Overview of Plant Life

© Jones & Bartlett Learning, LLC © Jones & BartlettOUTLINE Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Overview of • Concepts • Overview of Plant Structure Plant Life • Overview of Plant Metabolism © Jones & Bartlett Learning, LLC • Overview© of Jones Information & Bartlett in Plants Learning, LLC NOT FOR SALE OR DISTRIBUTION • OverviewNOT of Plant FOR Diversity SALE and OR DISTRIBUTION LEARNING OBJECTIVES Evolution After reading this chapter, students will be able to: • Overview of Plant Ecology • Describe the basic internal and external organization of plants. Box 2-1 Alternatives: Familiar Plants and • Compare© Jones plant & and Bartlett human Learning,metabolism. LLC © JonesSome & BartlettConfusing Learning, Look-Alikes LLC • ListNOT three FORsources SALE from whichOR DISTRIBUTION plants receive information. NOT BoxFOR 2-2 SALEAlternatives: OR PlantsDISTRIBUTION Without • Define and give examples of haploid and diploid plants. Photosynthesis • Explain the concept of clades. Box 2-3 Plants and People: Toxic Plants • Describe the interconnected dynamic between photosynthetic Box 2-4 Botany and Beyond: Noah’s Flood © Jones & organismsBartlett andLearning, organisms LLC that respire. © Jones & Bartlett andLearning, Population LLC Biology NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Did You© Jones Know? & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Chapter OpenerNOT Image: FOR The SALEhabitat here OR in DISTRIBUTION Yellowstone National Park changed dramatically • Plants, as distinct from algae, have existed for more than and suddenly in 1959. An earthquake caused 420 million years. this landslide, which blocked the Madison River, • Photosynthesis captures energy in sunlight and is almost the creating a lake and drowning the trees in the only© sourceJones of & energy Bartlett for all Learning, life on Earth. LLC © Jonesright foreground.& Bartlett Although Learning, the landslide LLC looks • There are almost 297,000 species of living plants and about barren, small plants are growing and life is NOT FOR SALE OR DISTRIBUTION NOT FORrecovering. SALE OR DISTRIBUTION 1,260,000 species of animals. • Plants are adapted to live everywhere on land in extraordinarily diverse conditions except where it is severely cold (under permanent snow and ice) or dry (parts of the Sahara Desert). © Jones &• PlanBartlettts defend Learning, themselves LLC from herbivores with spines ©and Jones poisons & Bartlett Learning, LLC NOT FOR SALEbut simultaneously OR DISTRIBUTION provide food for animals that pollinateNOT them. FOR SALE OR DISTRIBUTION 22

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❚❚ Concepts © Jones Anyone& Bartlett reading Learning, this text is probably LLC familiar with animal © Jones & Bartlett Learning, LLC NOT FORlife. SALE We each OR know DISTRIBUTION quite a bit about our own body, our organs,NOT FOR SALE OR DISTRIBUTION our metabolism, and the way in which we inherited DNA from our parents. We know that all humans are members of one extremely diverse species, Homo sapiens, a species in which individuals differ from each other in almost every possible character such as height,© athletic Jones ability, & Bartlettintelligence, Learning, health, LLC © Jones & Bartlett Learning, LLC talent, interests, goals, ambitions,NOT FOR spirituality, SALE and OR more. DISTRIBUTION We NOT FOR SALE OR DISTRIBUTION know that we had ancient ancestors, hominids who preceded the first Homo sapiens, and we had ancient relatives such as Homo neanderthalensis (Neanderthal Man) and Homo habilis. These other members of Homo are extinct now, but several distant relatives© Jones such as& chimpanzees,Bartlett Learning, orangutans, andLLC gorillas are © Jones & Bartlett Learning, LLC part ofNOT our evolutionary FOR SALE family. OR Most DISTRIBUTION of us are probably not too NOT FOR SALE OR DISTRIBUTION familiar with our own ecology except that we are social animals (we live in cities and do things in groups), we consume a large part of Earth’s resources, and produce harmful pollution. © Jones & BartlettBeyond our Learning, knowledge ofLLC our own biology, most of us are© Jones & Bartlett Learning, LLC also familiar with the biology of other animals such as dogs, NOT FORcats, SALE mosquitoes, OR DISTRIBUTION bees, whales, and so on. Even if this is the NOT FOR SALE OR DISTRIBUTION first biology text you have ever read, you are almost certainly a knowledgeable biologist already. Your knowledge of animal biology is an excellent foun- FIGURE 2-1 Shoot tip of cottonwood (Populus deltoides) in late dation for learning about© plant Jones biology. & BartlettPlant life is Learning,based on LLCautumn. It has a central stem with© 15 Jones leaves attached & Bartlett (only the Learning, LLC all the same fundamental principles that underlie the lives of petioles are visible in this close-up view); each petiole attaches animals, fungi, and all otherNOT living FOR beings. SALE Of course, OR DISTRIBUTION plants to the stem at a node. Five nodesNOT each contain FOR one SALE prominent OR DISTRIBUTION do many things differently, but let your knowledge of your axillary bud, each covered with protective bud scales. The very tip own biology guide your study of plant biology. And always of the shoot has a terminal bud. Bud scales protect the delicate keep the two fundamental questions in mind: What are the cells at the center of each bud; after surviving the winter, these alternatives? What are the consequences of each alternative? five axillary buds will grow and produce many small flowers. In © Jones & Bartlett Learning, LLC springtime, the© terminalJones bud & willBartlett grow as aLearning, continuation ofLLC the NOT FOR SALE OR DISTRIBUTION shoot, producingNOT more FOR leaves, SALE nodes, andOR internodes, DISTRIBUTION making the ❚❚ Overview of Plant Structure branch longer. Think about the many types of plants you know. Trees, garden TABLE 2-1 Organs That Comprise Most Plants flowers, grass, bulbs, cacti, and vines for example. Tremen- © Jones &dous Bartlett diversity Learning,is present, but ifLLC we examine each of these, we© JonesVegetative & Bartlett organs Learning, RootsLLC find they all share the same pattern of body organization. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONStems With only a few exceptions, the body of every plant is organized in the following simple way. Leaves Almost every plant consists of one or several stems, each Reproductive organs of flowers Sepals of which has leaves attached at regions called nodes (FIGURE 2-1; TABLE 2-1). Just above© Jones each attachment & Bartlett point Learning,is an axil- LLC © JonesPetals & Bartlett Learning, LLC lary bud, some of whichNOT develop FOR into branches SALE whereasOR DISTRIBUTION others NOT FOR SALE OR DISTRIBUTION Stamens develop into flowers, but many axillary buds remain dormant and never do anything. Stems are typically slender, less than 5 Carpels mm in diameter, but wide ones occur in cacti and other desert plants that use them to store water (FIGURE 2-2). Some stems are extremely© Jones short, & asBartlett in carrots Learning, and cabbage, butLLC vines and texture and in© being Jones evergreen & Bartlett or deciduous, Learning, but the import LLC- bambooNOT typically FOR have SALE extremely OR longDISTRIBUTION stems. ant thing is thatNOT almost FOR all stemsSALE bear OR leaves; DISTRIBUTION they are a part of Leaves, too, are diverse. They range in size from the the fundamental pattern of plant bodies. Hornworts and some gigantic leaves of palms to ones that are merely large, as in liverworts are plants that never produce any kind of leaf at all. Philodendron, down to ones that are small, such as those of Another aspect of the fundamental organization of rosemary (FIGURES 2-3 and 2-4). Although cacti are often plants is that almost all plants have roots (FIGURE 2-5). In © Jones &said Bartlett to be leafless, Learning, all have tiny LLC foliage leaves that are almost © Jonesalmost &all Bartlettplants, roots Learning, are confined LLC to one end of the stem, NOT FORmicroscopically SALE OR DISTRIBUTIONsmall. Leaves vary greatly in shape and NOTbut FOR it is also SALE common OR to DISTRIBUTION see roots emerge along a stem, such Overview of Plant Structure 23

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FIGURE© Jones2-2 Like many& Bartlett plants adapted Learning, to deserts, LLC golden barrel FIGURE 2-4 ©This Jones is a very & common Bartlett weed Learning, in most gardens, LLC and cactusNOT (Echinocactus FOR grusoniiSALE) storesOR DISTRIBUTIONwater in very broad stems you may haveNOT already FOR spent someSALE time OR pulling DISTRIBUTION it up. It is in the composed of thousands of water-filled cells. Spines prevent genus Chamaesyce (pronouned cam ee SIGH see), and plants animals from eating the cactus to obtain water. Because the tend to grow flat against the ground, often with a circular form stem is so broad, it is exceptionally heavy, so succulent plants only a few centimeters in diameter. These leaves are tiny, only typically branch much less than nonsucculent plants: This plant about 1 mm across. The plant is covered in flowers. Plants of © Jones &has Bartlett only one stem, Learning, somewhat likeLLC the single stem of a palm tree.© JonesChamaesyce & Bartlett bloom even Learning, while only a fewLLC weeks old; each flower The spines are highly modified bud scales (compare with the bud here is emerging from an axillary bud. NOT FORscales SALE of cottonwood OR DISTRIBUTION in Figure 2-1), so each spine cluster is an NOT FOR SALE OR DISTRIBUTION axillary bud. The leaf that makes the axil for each spine cluster is microscopic and cannot be seen here.

© Jones & Bartlett Learning, LLC © JonesFIGURE & 2-5 Bartlett These onions Learning, are whole LLCplants, with roots at one end, the shoot at the other. Onion leaves are a bit unusual NOT FOR SALE OR DISTRIBUTION NOTbecause FOR theySALE are part OR of DISTRIBUTIONa shoot called a bulb: The purple portion FIGURE 2-3 Like many palms, Bismarkia nobilis has gigantic of each leaf (the leaf base) is swollen and stores water and leaves. Each petiole is more than 1 m long, and the giant leaf nutrients, the green upper portion carries out photosynthesis. blades are both long and wide. An individual palm usually has many fewer leaves than do other trees, but because each palm leaf is so large, palms have© as Jones much total & photosyntheticBartlett Learning, surface LLCcarry out sexual reproduction. When© Jones a plant &is readyBartlett to repro Learning,- LLC area as do many other plants. For some unknown reason, many duce, reproductive organs develop. The reproductive organs people refer to the leavesNOT of palms FOR and ferns SALE as “fronds” OR DISTRIBUTIONeven NOT FOR SALE OR DISTRIBUTION though they are true leaves. of most ferns are barely distinguishable from vegetative organs: They are basically just foliage leaves that produce sporangia on their underside (FIGURE 2-8). Without turning a leaf over to as in ivy that climbs on fences and trees, attached to them see if it has sporangia and spores, one would never guess that by numerous© Jones groups & Bartlettof roots (FIGURE Learning, 2-6). Underground LLC it is not just an© ordinaryJones leaf. & Bartlett Reproductive Learning, structures are LLC a bit stemsNOT like those FOR of irisesSALE and OR ginger DISTRIBUTION also produce roots along more complexNOT in the FOR seed plants. SALE Conifers OR DISTRIBUTION make seed cones their length rather than at just one end (FIGURE 2-7). Roots and pollen cones, angiosperms make flowers (FIGURES 2-9 are less varied than stems or leaves, and most roots are usu- and 2-10). Only flowers will be discussed here in this overview. ally easy to recognize as roots. Details about conifers and ferns are presented in later chapters. Roots, stems, and leaves are the vegetative organs of a Flowers appear to be so diverse it seems as if there must © Jones &plant. Bartlett By that, weLearning, mean that they LLC are responsible for obtaining© Jonesbe thousands & Bartlett of types. Learning, Just think of how LLC diverse roses, irises, NOT FORenergy SALE and OR materials DISTRIBUTION for growth and survival, but they do notNOT lilies, FOR snapdragons, SALE OR and DISTRIBUTIONpetunias are. But here, too, there is only 24 Chapter 2: Overview of Plant Life

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 2-6 This is an old vine of poison ivy (Toxicodendron radicans), climbing up a tree trunk, attached to it by clusters of adventitious roots. These roots mostly just attach to the tree’s B bark, and the poison ivy also has ordinary roots at the base of FIGURE 2-8 (A) This is the upper surface of a leaf of sword the vine that absorb water and nutrients. Even though this part © Jones & Bartlett Learning, LLC fern (Polystichum© Jones munitum ),& and Bartlett it carries outLearning, photosynthesis. LLC of the poison ivy plant is so old that it has shed its leaves, it is still But in many ferns, some leaves also produce spores on their extremelyNOT poisonous FOR SALE and should OR not DISTRIBUTION be handled. undersides, andNOT it is necessaryFOR SALE to turn ORthe leaf DISTRIBUTION over to be certain. (B) This is the lower surface of a sword fern leaf, and it is involved in reproduction. Each of the round structures is called a sorus (plural, sori; pronounced SOAR eye), a group of dozens of minute structures (sporangia) that each produce spores. Only some of © Jones & Bartlett Learning, LLC © Jonesthe leaves & ofBartlett sword ferns Learning, have sporangia; LLC other leaves would NOT FOR SALE OR DISTRIBUTION NOThave FOR nothing SALE special OR when DISTRIBUTION turned over.

one basic organizational plan, and once you know it, you can easily understand almost any flower. Each flower is a reproductive shoot; that is, each flower has a short stem with leaflike © Jones & Bartlett Learning, structuresLLC attached to it. Sepals protect© Jones the rest & ofBartlett the flower Learning, as LLC NOT FOR SALE OR DISTRIBUTIONit develops, and petals attract pollinatorsNOT FOR after SALEthe sepals OR spread DISTRIBUTION apart allowing a flower to open. Above the petals are stamens that produce pollen, followed by carpels (often called pistils) that each contain one or more ovules (FIGURE 2-11). Stamens and carpels are essential because each pollen grain contains two FIGURE© Jones 2-7 This &is aBartlett rhizome of gingerLearning, (Zingiber LLC officinale) sperm cells and© Joneseach ovule & contains Bartlett an egg Learning, cell. Insects, LLCbirds, that was purchased at a grocery store, planted for a few weeks, and wind carry pollen from stamens to carpels, usually from and thenNOT dug FOR up for examination.SALE OR By DISTRIBUTION planting the rhizome, we NOT FOR SALE OR DISTRIBUTION activated it and stems grew upward; new adventitious roots the stamens of one plant to the carpels of a different plant of the spread in all directions but would have soon turned downward. same species. After a sperm cell fertilizes an egg cell, an embryo All new parts are white because plants cannot synthesize and the surrounding tissues grow to be a seed while at the same chlorophyll while in the dark. The new adventitious roots emerge time some carpel tissues develop into a fruit. In angiosperms, © Jones &from Bartlett the new shoots: Learning, As each shootLLC grows upward toward the © Jonesall seeds & develop Bartlett inside Learning, a fruit—that isLLC one of the defining char- NOT FORlight, SALE it makes OR its DISTRIBUTIONown particular supply of roots. NOTacters FOR of beingSALE an angiospermOR DISTRIBUTION (FIGURE 2-12). Overview of Plant Structure 25

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Most of us have no trouble© Jonesrecognizing & Bartletta very large Learning, num- LLC“Grass” is used correctly almost© allJones the time & but Bartlett applied to Learning, LLC ber of plants, at least whileNOT they FOR are in bloomSALE or OR if certain DISTRIBUTION the wrong groups sometimes. NOTLawn grassesFOR areSALE grass (exceptOR DISTRIBUTION characteristic features are present. Apples, oranges, peaches, for clover), as are wheat, rye, barley, rice, corn, and even and pears are fruits we all recognize, and if they are still on giant bamboo (no, it is not a tree; it is a giant, very tough their trees, we have no trouble recognizing the whole plant grass; FIGURE A14). If you see a grasslike plant growing in as well (FIGURE A1). Strawberries are very familiar, but you standing water, however, it is almost certainly a sedge and might© be Jones initially uncertain& Bartlett if you Learning, saw them growing LLC on the not a grass (©FIGURE Jones A15 &). BartlettSedges are distinguishedLearning, from LLC soil surface,NOT supportedFOR SALE by thin, OR delicate DISTRIBUTION stems (such stems grasses by feelingNOT the FOR stems SALE and remembering OR DISTRIBUTION this mne- are runners). Daisies (often called asters) are also usually monic: “Sedges have edges, but grasses are round from tip easy to recognize because even though there are hundreds of to ground.” Using the wrong name is not a terrible problem; species, most all look like the one in FIGURE A2. The same few of us know the names of very many plants, and as we is true for morning glories (FIGURE A3), lilies, water lilies, discuss plants with our friends, using exactly the right name © Jones &and Bartlett many others Learning, (FIGURE A4 LLC). © Jonesis not &often Bartlett necessary. Learning, It is like using LLC the word “bug” for NOT FOR SALEIn contrast, OR DISTRIBUTIONseveral groups of plants can cause confu- NOT spiders,FOR SALEinsects, andOR various DISTRIBUTION other tiny animals. sion. Many people believe any plant that is succulent and The situation is similar with the words we use for plant spiny is a cactus (FIGURE A5), whether they are looking parts. You will often hear the word “frond” when people talk at an Agave (FIGURE A6), a Yucca (FIGURE A7), an Aloe about the leaves of palms or ferns. “Frond” is just fine, but it (FIGURE A8), or one of the succulent spurges—“spurge” is not a precisely defined term; it is just that for some reason, may be an unfamiliar name© Jones and refers & to Bartlett members Learning,of the LLCsome people use it instead of the© Jonesword “leaf” & forBartlett palms and Learning, LLC genus Euphorbia (FIGURENOT A9). FOR These SALE are all succulent, OR DISTRIBUTION most ferns. Similarly, “stalk” is not aNOT precisely FOR defined, SALE technical OR DISTRIBUTION are spiny, and most live in deserts, but agaves and yuccas are term, and neither are “rind,” “peel,” “skin,” and several others. much more closely related to lilies and irises than to cacti Just keep in mind that some precise botanical terms such as (their long, thick leaves are extreme versions of lily leaves). “stem” and “leaf” are the same as ordinary English words, Furthermore, although many botanists also mistakenly call and some like “epidermis” are identical to the terms used by spurges© cacti,Jones the spurges& Bartlett are in aLearning, completely different LLC family zoologists, even© Jones though &a plant Bartlett epidermis Learning, is completely LLC dif- and areNOT mostly FOR native SALE to Africa, OR whereas DISTRIBUTION cacti are native ferent fromNOT an animal FOR epidermis. SALE If OR you haveDISTRIBUTION already studied to the Americas. I heard a person guess that a giant Agave a lot of zoology, be very careful as you come across botanical americana must be an Aloe vera: He made a really good words that are the same as zoological or medical words: The guess because the plants do look alike, even though that meanings are probably very different. agave is hundreds of times larger than an aloe. Plants have common names and scientific names, and © Jones & BartlettDoes it really Learning, matter if people LLC confuse these plants? © Jonesa great & deal Bartlett of effort Learning, is made to ensure LLC that each species of NOT FORNot SALE really, ORbecause DISTRIBUTION they are correct that the plant is a large, NOT plantFOR or SALE animal orOR any DISTRIBUTION other organism has only one scien- succulent spiny desert plant. If it is important to have the tific name. For some plants the name of the plant’s genus correct name, they can ask at a garden center or a botany is the same as its common name; agaves are in the genus department or perform a Google image search. Agave, and citruses are in the genus Citrus. When we write Other plants that are often confused with each other are the common name, we do not capitalize or italicize it, roses and camellias (the ©flowers Jones are &quite Bartlett similar; FIGURE Learning, LLCbut we do if we are referring ©to theJones scientific & Bartlett name of the Learning, LLC A10) and palm trees, cycads,NOT and FOR ferns SALE (some have OR similar DISTRIBUTION genus: oranges, lemons, and limesNOT are FOR all citruses SALE in OR the DISTRIBUTION shapes and leaves; in fact, in areas where cycads are com- genus Citrus. Lemons are Citrus limon, oranges are Citrus mon, people often use cycad leaves instead of palm leaves sinensis, and limes are Citrus latifolia. It is natural to think on Palm Sunday; FIGURE A11). People often describe most of “limon” as the species name of lemons, but that is not aquatic plants as “moss,” but true mosses almost never grow exactly correct; the species name is Citrus limon. The sci- in water:© Jones Long stringy & Bartlett ones that floatLearning, are usually LLC algae; those entific name© Jonesof all species & Bartlett always has Learning, two words: LLCThe first with stems,NOT leaves,FOR andSALE flowers OR are DISTRIBUTION flowering plants; and is the genusNOT name FOR and the SALE second OR is the DISTRIBUTION species epithet; a few very small water plants are ferns. Many of us (even therefore, the species name is the genus + species epithet. professional botanists) use the word “moss” for any very tiny When I mentioned agaves above I used the common name plant whether it is a moss or just a small plant that resembles agave, the genus name Agave, and the scientific name of a moss (FIGURES A12 and A13). the giant agave, Agave americana. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 26 Chapter 2: Overview of Plant Life

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7 © Jones & Bartlett Learning, LLC8 © Jones & Bartlett9 Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

10 11 12 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

13 14 © Valentina De Menego/Shutterstock 15 FIGURE A (1) An orange tree. (2) Daisies. (3) Morning glories. (4) Oxblood lilies. (5) All the tall or globe-shaped plants are cacti; those with thick gray, yellow, or green leaves are agaves. (6) Agave americana. (7) Yucca torreyi. (8) Aloes. (9) A spurge (Euphorbia, not a cactus). © Jones &(10) Bartlett Camellia flower. Learning, (11) A cycad, LLC often called a “sago palm.” (12) Selaginella© Jones peruviana & Bartlett (despite Learning, the species epithet LLC this plant grows in NOT FORTexas, SALE not Peru;OR not DISTRIBUTION a moss). (13) A liverwort (Frullania inflata, notNOT a moss). FOR (14) Bamboos SALE are OR giant DISTRIBUTION grasses. (15) A sedge, not a grass. Overview of Plant Structure 27

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Stigma

Ovary

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 2-11 Carpels consist of three parts: a stigma, a style, and an ovary. Within the ovary is one or several ovules, each of which contains an egg cell (only one ovule is shown here). If the carpel is pollinated and the egg is fertilized, the fertilized egg © Jones & Bartlett Learning, LLC © Jonesdevelops & into Bartlett an embryo, Learning, the rest of the LLC ovule develops into a seed, and the ovary develops into a fruit. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 2-9 This is a seed cone of a pine tree (Pinus). It was pollinated many months ©ago, Jones and now & the Bartlett cone is growing Learning, larger, LLC © Jones & Bartlett Learning, LLC as are the many seeds inside it. Tough, hard cells and sticky resin protect the seeds as they NOTgrow. When FOR the SALE seeds are OR mature, DISTRIBUTION the NOT FOR SALE OR DISTRIBUTION cone will expand enough to cause the scales to separate and allow the seeds to fall out.

Sepal © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 2-12 A seed pod of coral bean (Erythrina herbacea) is a FIGURE 2-10 This is a simplified, diagrammatic representation fruit similar to the pod of a bean or pea: When it is ripe, it opens of the four basic organs of flowers. © Jones & Bartlett Learning, LLC by twisting, releasing© Jones the mature& Bartlett seeds. This Learning, is a dry fruit, LLCin contrast to an apple or tomato, which are fleshy fruits. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION If flowers have this fundamental organization of sepals, petals, stamens, and carpels, how can there be so many types insects, then having brightly colored petals helps a flower to of flowers? And especially so many flowers in which this orga- be noticed. But if pollen is carried by wind, then it is a waste nization is not easy to see? One reason is that in many flowers, of resources to produce petals: Wind-pollinated flowers often © Jones &one Bartlett or two of theseLearning, organs are LLC extremely underdeveloped or © Joneslack petals & Bartlett completely Learning, (FIGURES 2-13 LLC and 2-14). Similarly, NOT FOReven SALE absent OR completely. DISTRIBUTION If a flower is pollinated by birds or NOTcertain FOR plants SALE produce OR clustersDISTRIBUTION of tiny flowers, and rather than 28 Chapter 2: Overview of Plant Life

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© Jones & Bartlett Learning, LLC FIGURE 2-15© InJones this flower & Bartlettof Datura wrightii Learning,, the five greenLLC NOT FOR SALE OR DISTRIBUTION sepals have fusedNOT to eachFOR other, SALE making OR a tube, DISTRIBUTION and the five white petals have fused to each other, making a second tube. The tip of each petal remains separate and recognizable. The five stamens do not fuse to each other and are distinct. The five carpels have fused to each other, so only a single style and stigma are present. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TABLE 2-2 Tissues That Comprise Most Plants*

Epidermis

FIGURE 2-13 These are three clusters of ash (Fraxinus) flowers; Cortex† ash is wind pollinated, so© there Jones is no need & Bartlett for large colorful Learning, petals LLC © Jones & Bartlett Learning, LLC to attract animal pollinators. Each of these three clusters consists Vascular tissues almost entirely of anthers,NOT the part FOR of a stamen SALE that OR produces DISTRIBUTION a. Xylem NOT FOR SALE OR DISTRIBUTION pollen. b. Phloem Pith (occurs only in stems)2

Mesophyll (occurs only in leaves and flowers)2 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Secondary xylemNOT (wood) FOR SALE OR DISTRIBUTION Secondary phloem (occurs as part of bark)

Cork (occurs as part of bark)

* Reproductive structures such as flowers and cones have additional © Jones & Bartlett Learning, LLC © Jonestissues. & These Bartlett are discussed Learning, in Chapters 10 LLC and 23. † NOT FOR SALE OR DISTRIBUTION NOT FOR People oftenSALE speak OR of cortex, DISTRIBUTION pith, and mesophyll as tissues but technically each is a region of an organ, and each might be composed of various tissues. For example, leaf mesophyll is the region between the upper epidermis and the lower epidermis, and it consists of both photosynthetic tissue (the green cells) and vascular tissue (the leaf veins). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC FIGURE 2-14 We often NOTnever notice FOR the SALE flowers OR of wind- DISTRIBUTIONIn addition, flowers differNOT from eachFOR other SALE because OR in DISTRIBUTION pollinated trees because they are very small, lack petals, and some the various organs are fused to each other; whereas in are located so high in trees. But after they release their pollen, other flowers all organs remain separate and distinct. It is the flowers are abscised from the trees and fall. Shown here are common to see all the sepals of a flower fused to each other long, stringlike clusters of the staminate flowers of pecan (Carya such that they form a tube, and petals often fuse to each other illinoensis© Jones); although & we Bartlett often do notLearning, notice them LLC while still in the (FIGURE 2-15© ).Jones Such fusions & Bartlett almost never Learning, occur among LLC trees,NOT they are FOR hard to SALE miss when OR on DISTRIBUTION sidewalks, cars, and roofs. leaves. We couldNOT go FORon listing SALE flower OR modifications, DISTRIBUTION but the important thing is that each and every type of flower, no matter how exotic, is just a modification of one basic plan. making sepals for each flower, they just make one set of large The internal organization of plants is even simpler and bracts that protects the entire cluster; these flowers lack sepals. more uniform than the external form (TABLE 2-2). While © Jones &Stamens Bartlett and carpels Learning, can also LLCbe missing from the flowers of© Jonesyoung, &every Bartlett part of a Learning, plant—every root,LLC stem, leaf, petal, NOT FORcertain SALE species. OR DISTRIBUTION NOTand FOR all the SALE rest—consists OR DISTRIBUTION of an external epidermis, internal Overview of Plant Structure 29

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Vascular Pith Cortex bundles Fiber cells © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Phloem

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 2-16 This cross-section of a buttercup (Ranunculus) shows an arrangement of tissues that occurs in almost all seed plant stems: epidermis, cortex, a ring of vascular bundles, and pith in the center. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORground SALE tissues, OR andDISTRIBUTION vascular tissues (FIGURE 2-16). Simi- NOT FOR SALE OR DISTRIBUTION lar to our own epidermis, the epidermis of a plant protects the body from bacteria and fungi, and it inhibits water from FIGURE 2-17 This is a light microscope view of a vascular evaporating out of the body. “Ground tissue” is a somewhat bundle in a stem of sunflower (Helianthus annuus). The eight large vague term that refers to inner tissues in general. The ground round open cells at the bottom are xylem vessels that carry water tissue in roots is cortex; ©in stemsJones it is & both Bartlett pith and Learning,cortex; and LLCupward from the root to leaves and© flowers.Jones Just & Bartlettabove these Learning,are LLC small, angular phloem cells that carry sugar. The upper mass of in leaves and flowers it NOTis referred FOR to asSALE mesophyll. OR GroundDISTRIBUTION NOT FOR SALE OR DISTRIBUTION red cells are fiber cells that make a cap along the outer edge of tissues of stems are easy to see in potato tubers: Each tuber the phloem, not only giving the stem strength to stand upright, is a short, wide stem that consists of very broad pith and a but also to protect the phloem from insects that might try to eat moderately wide cortex. Leaves of Aloe have a thick succulent into it or suck the sap through a long proboscis, as aphids do. ground tissue, the watery mesophyll. Plants© Jones have two & distinctlyBartlett different Learning, vascular LLC tissues. © Jones & Bartlett Learning, LLC XylemNOT (pronounced FOR SALE ZY lem) OR transports DISTRIBUTION water and miner- NOT FOR SALE OR DISTRIBUTION als upward from roots to all aerial parts, especially leaves and flowers (FIGURE 2-17). The air around a plant absorbs most of that water but some of the water and all the minerals remain inside the plant for its own use. Phloem (pro- © Jones &nounced Bartlett FLOW Learning, em) carries LLCsugars and various organic © Jones & Bartlett Learning, LLC NOT FORcompounds SALE OR as well DISTRIBUTION as minerals and water throughout the NOT FOR SALE OR DISTRIBUTION plant. For example, leaves produce sugar by photosynthesis, and phloem carries most of that sugar out of the leaf into the stem; some is transported downward where it nourishes roots, while some is transported upward to flowers and fruits. Xylem and phloem© almostJones always & Bartlett occur together Learning, in a LLC © Jones & Bartlett Learning, LLC small number of vascularNOT bundles. FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION It can be confusing to compare the vascular systems of plants and animals without thinking about each carefully. We humans pump blood out of our heart into a single wide aorta, which then branches into many large arteries, each of which, in turn,© branchesJones into& Bartlett narrower arteriesLearning, that finally LLC branch FIGURE 2-18© ThisJones is a cross-section & Bartlett of a Learning,small wisteria vine, LLC and the many dark holes are vessels in the xylem. Each is the into arterioles and capillaries. No plant ever puts all its water, NOT FOR SALE OR DISTRIBUTION open end of aNOT long tube FOR that SALE runs deeply OR into DISTRIBUTION the stem, and the sugars, and minerals into just one large vascular bundle. Even other part of each tube extended far into the part of the stem the most slender stem will have 10 to 20 vascular bundles; this that was cut away. Even in this narrow young vine water is carried provides plants with safety through redundancy. If an insect by hundreds of vessels, and if one or two become damaged, the bites into a stem and breaks one or two vascular bundles, the rest can still function. Each year, the vine would add even more © Jones &stem Bartlett will still haveLearning, many others LLC that are intact and functional© Jonesvessels as& itBartlett made more Learning, wood along the LLC edge of this wood, just NOT FOR( FIGURESALE 2-18 OR). DISTRIBUTION NOTinterior FOR to SALE the bark. OR DISTRIBUTION 30 Chapter 2: Overview of Plant Life

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The description of plant structure to this point refers to young plants as well as to young growth at the ends of © Jones branches& Bartlett and roots.Learning, This is called LLC the primary plant body, and© Jones & Bartlett Learning, LLC NOT FORall SALE the tissues OR and DISTRIBUTION organs are produced by cells located at theNOT FOR SALE OR DISTRIBUTION very tips of stems and roots. Herbs are plants that have only this primary body; examples include lilies, lettuce, lawn grass, and ferns. Herbs are usually small plants that live only a few months before they reproduce and die. Woody plants are defined as those that produce© Jones a secondary & Bartlett body inside Learning, their LLC © Jones & Bartlett Learning, LLC primary body. This is easierNOT to FORunderstand SALE with OR less DISTRIBUTIONtechnical NOT FOR SALE OR DISTRIBUTION words: Woody plants are those that produce wood and bark (FIGURE 2-19). In an herb, all cells mature into epidermis, ground tissue, or vascular tissue; once these are formed, no immature cells are left. But in plants that will become woody, a sheet© of Jones cells runs & through Bartlett all the Learning, vascular bundles; LLC the © Jones & Bartlett Learning, LLC cells withinNOT thisFOR sheet SALE do not ORmature. DISTRIBUTION Instead they divide and NOT FOR SALE OR DISTRIBUTION produce new cells; this region is the vascular cambium. Cells produced to the inner side of the vascular cambium become wood (technically called secondary xylem); those on the outer side become secondary phloem (which is part of the bark). © Jones &All Bartlett vascular cambia Learning, share the LLC same basic organization, but can© Jones & Bartlett Learning, LLC NOT FORvary SALE greatly OR in the DISTRIBUTION speed with which they produce cells and NOT FOR SALE OR DISTRIBUTION in the amount of cells they produce. The vascular cambia of giant conifers and hardwood trees produce massive amounts of wood and bark, whereas those of roses and other shrubs produce much less. Woody plants also have cork cambia, sets FIGURE 2-20 This is Pereskia grandifolia, one of the few cacti of dividing cells that contribute© Jones waterproof, & Bartlett damage-resistant Learning, LLC © Jones & Bartlett Learning, LLC that still produce large, easily recognizable foliage leaves. The cork cells to the bark. NOT FOR SALE OR DISTRIBUTIONspines that emerge from its leaf axilsNOT are FORmodified SALE bud scales: OR DISTRIBUTION A word of caution before we leave this overview of There is an axillary bud there as we would expect, but the bud plant structure. Although almost all plants are organized as scales develop as spines, rather than as the typical scales as in described here, many plant parts have evolved such that they cottonwood (Figure 2-1). All plants produce at least two types of carry out unusual functions and have shapes that fool even leaves: foliage leaves and bud scales. professional© Jones botanists. & Bartlett The spines Learning, of cacti are modifiedLLC bud © Jones & Bartlett Learning, LLC scalesNOT of axillary FOR buds SALE even though OR DISTRIBUTION they have almost no fea- NOT FOR SALE OR DISTRIBUTION tures typical of a bud scale (FIGURE 2-20). The beautiful white flowers rather than being one single flower as it would appear or yellow flowers of daisies are actually entire groups of tiny (see Figure A2 in Box 2-1). And palm trees, despite being big, hard, and long-lived, are herbs: They never make even a single cell of wood nor do they have a vascular cambium. Plant struc- © Jones & Bartlett Learning, LLC © Jonesture is one& Bartlett of the easiest Learning, aspects of biology LLC to study because NOT FOR SALE OR DISTRIBUTION NOTplants FOR do SALE not run orOR fly DISTRIBUTION away; we can walk up to them and look at them closely. Most structures are easy to see with the naked eye, even more are visible with an inexpensive hand lens.

© Jones & Bartlett Learning, ❚LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION❚ Overview of PlantNOT FOR SALE OR DISTRIBUTION Metabolism All organisms—plants, animals, fungi, and all the rest—must take in energy and raw materials from their environment. © Jones & Bartlett Learning, LLC This generalization© Jones has no& exceptions Bartlett whatsoever; Learning, there LLC is no NOT FOR SALE OR DISTRIBUTION alternative. WeNOT animals FOR take SALE in both energyOR DISTRIBUTION and raw materi- FIGURE 2-19 It is easy to distinguish woody plants from als as the organic materials we call food. Plants do not eat, of herbs here: The trees are woody plants, the grasses are herbs. course; instead they take in resources through several separate Even though grasses may live for many years, they never form processes. Energy is provided by sunlight and is captured by the secondary xylem or phloem (they never make wood or bark), process of photosynthesis. The bulk of a plant’s body is com- © Jones &whereas Bartlett almost Learning, all trees begin toLLC add secondary xylem and © Jonesposed of& organic Bartlett molecules Learning, that can allLLC be traced back to the NOT FORphloem SALE to theirOR bodies DISTRIBUTION even when they are only a few months old.NOTreaction FOR ofSALE carbon ORdioxide DISTRIBUTION and water during photosynthesis. Overview of Plant Metabolism 31

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Are ordinary stems and ©foliage Jones leaves & really Bartlett adaptations Learning, that LLCphotosynthesis, mutations that ©curtail Jones leaf development & Bartlett Learning, LLC improve photosynthesis?NOT Or do FOR plants SALEhave plantlike OR DISTRIBUTIONstructure became beneficial: Most holoparasitesNOT FOR have eitherSALE small, OR scale DISTRIBUTION- just because that is the way things are? It is easy to take really like leaves or none at all. Dodder (Cuscuta) is one of the few common things for granted and not even ask ourselves if there holoparasites that has any ordinary plantlike features left in its are alternatives. We can create many models and consider body (FIGURE A). It has long, slender stolonlike shoots with theoretical aspects, but we always want to verify our theories tiny leaves; it twines around host plants, inserting haustoria with real© Jones data, with & empirical Bartlett evidence. Learning, That is LLCa principle of (modified roots)© Jones into them & Bartlettand then growing Learning, onward. LLCIts the scientificNOT FOR method. SALE To see ORjust howDISTRIBUTION much of ordinary plant plantlike featuresNOT of FORnodes andSALE internodes OR DISTRIBUTION seem to be neces- structure is the result of natural selection that improves pho- sary for it to spread from branch to branch of a host or from tosynthesis, we need plants that do not photosynthesize, that one plant to another. are heterotrophic, and that have been heterotrophic for so long Most holoparasites are subterranean. Their seedling roots that their bodies have had many millions of years to evolve invade host roots, then the parasite’s embryo develops into © Jones &without Bartlett being restrictedLearning, by the LLC need to photosynthesize. The© Jonesa rhizomelike & Bartlett shoot with Learning, small, tough, LLC protective, scalelike NOT FORplants SALE we need OR are DISTRIBUTION parasitic plants. NOTleaves. FOR Being SALE underground, OR DISTRIBUTION it is invisible to herbivores, and Approximately 4,000 species of parasitic plants occur temperatures and humidity are more stable, less variable than in about 18 families (TABLE A), and the ability for one plant above ground. Many photosynthetic plants also have rhi- to attack another has arisen evolutionarily about 12 times. zomes, but many of their axillary buds grow upward as aerial, Because there have been a dozen different starting points and chlorophyllous branches; this never occurs in holoparasites. A because some groups had© moreJones time & than Bartlett others to Learning,become LLCfew of their axillary buds grow ©above Jones the soil & surface Bartlett as inflo Learning,- LLC adapted to their hosts, parasiticNOT FOR plants SALEdiffer widely OR fromDISTRIBUTION each rescences, displaying flowers toNOT pollinators FOR (FIGURE SALE B ).OR DISTRIBUTION other in structure, physiology, and so on. Two fundamental In other holoparasite species, development is even less types of parasitic plants occur. like that of ordinary plants: The subterranean “rhizome” has Hemiparasites have chlorophyll and produce all, or at no leaves at all, no axillary buds, nodes, or internodes. The least part, of their own glucose; they merely obtain water, growing apex consists of a mass of meristematic cells but has minerals,© Jones and perhaps & Bartlett some organic Learning, compounds LLC from their neither leaf primordia© Jones nor & a Bartlettroot cap. Internally, Learning, the “rhi LLC- hosts.NOT Hemiparasites FOR SALE still have OR leaves DISTRIBUTION with stomata and rather zome’s” tissuesNOT are not FOR typical SALE of either OR root DISTRIBUTION or shoot, having ordinary stems. Their roots, however, penetrate the epidermis neither a single ring of bundles typical of a stem nor a central or bark of host plants rather than soil. mass of xylem as ordinary roots do. Even the surface is just Holoparasitic plants have neither chlorophyll nor photo- a rough, irregular proliferation of cells rather than a smooth synthesis: All of their ATP is produced by aerobic respiration sheet of epidermis. The term “runner” is often used to indicate © Jones &of glucoseBartlett obtained Learning, from the LLChost plant, and they probably © Jonesthat it is& not Bartlett an ordinary Learning, plant organ. LLC NOT FORneed SALE little reducingOR DISTRIBUTION power. In all cases, after the ancestral NOT FORSeveral SALE holoparasitic OR DISTRIBUTION plants live entirely within the body parasitic plants became holoparasitic and lost any need for of their hosts. After their seedling root penetrates the host, the rest of the embryo dies. The “roots” grow deeper into the TABLE A Families That Contain Parasitic Plants host, penetrating its cortex, phloem, xylem, and pith, and they make up 100% of the parasite’s body. The parasite has no Balanophoraceae © Jones & Bartlett Learning, shootLLC at all. The term “roots” is© in Jones quotation & marksBartlett because Learning, LLC these structures have no features typical of roots. Technically Hydnoraceae NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION this is an endophyte, a plant that lives within another. The Loranthaceae (mistletoes native to North America) endophyte of the mistletoe Tristerix aphyllus, which grows inside the cactus Trichocereus chilensis, consists only of a Orobanchaceae branching web of uniseriate filaments of parenchyma cells; Rafflesiaceae© Jones & Bartlett Learning, LLC after some ©months Jones (?) or & years Bartlett (?), the Learning,filaments become LLC NOT FOR SALE OR DISTRIBUTION multiseriate NOTas their FOR cells undergo SALE longitudinal OR DISTRIBUTION divisions Santalaceae (FIGURE C). At some point, a bit of phloem develops and an Viscaceae (mistletoes native to Europe) occasional, isolated vessel element—the entire plant body has no roots, stems, leaves, epidermis, cortex, pith, and only a few Note: Parasitic plants occur in many families, but these listed here have some of the most common or most familiar parasites. For more cells of xylem and phloem. Detailed studies are needed, but it © Jones &information Bartlett and Learning, excellent images, LLC go to The Parasitic Plant Connec- © Jonesappears & that Bartlett every surface Learning, cell of the LLC endophyte body absorbs NOT FOR tionSALE (www.parasiticplants.siu.edu/index.html). OR DISTRIBUTION NOTwater, FOR minerals, SALE and OR organic DISTRIBUTION molecules from the host’s 32 Chapter 2: Overview of Plant Life

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tissues. With the entire body being absorptive, there is little merely obtain glucose from their hosts and then use various need for conduction. When stimulated to flower, parenchyma types of respiration and anabolic pathways to synthesize all © Jones cells& Bartlett just below Learning, the host epidermis LLC proliferate into a nod- © Jonesother organic & Bartlett molecules. Learning, It would not LLC be surprising, however, NOT FORule SALE of callus, OR an adventitiousDISTRIBUTION inflorescence apical meristem NOTto FOR find some SALE species OR of DISTRIBUTIONparasitic plants that have become forms, and then it breaks its way through the host epidermis. dependent on their hosts for at least some amino acids, lipids, Because it has an ordinary apical meristem, the inflores- or vitamins. Despite being so modified, the endophytic bodies cence has epidermis, cortex, a ring of vascular bundles, and of holoparasites are healthy, thriving, and well adapted to pith (but no chlorophyll). Endophytes of Viscum minimum, respiration-based metabolism in a unique environment. Pilostyles thurberi, and several© Jones Rafflesia & Bartlettspecies are Learning,similar LLCHoloparasitic plants show ©us thatJones many & features Bartlett of ordi Learning,- LLC (FIGURE D). NOT FOR SALE OR DISTRIBUTIONnary plants must be very expensiveNOT and FOR risky: SALEAfter a ORplant DISTRIBUTIONhas After a green photosynthetic photoautotroph has pro- an alternative to photosynthesis, ordinary plant features are duced glucose, it then synthesizes all other organic compounds no longer adaptive, and mutations that prevent their develop- needed for its structure and metabolism (see Figure 2-21). It ment are advantageous. On the other hand, for plants that do may be that some holoparasites do the same thing; they may photosynthesize, plantlike bodies are worth the trouble. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE A The slender orange stems are Cuscuta, a holoparasite FIGURE B Prosopanche (pronounced pro so PAN key) americana that still has leaves and stems, but its internodes are extremely is holoparasitic, and most of its highly modified body remains long and slender and its leaves are tiny. It is producing underground; it has no need for photosynthesis, obtaining all its adventitious roots that develop as haustoria, penetrating to the water and nutrients from the roots of its host. This flower is also vascular© tissuesJones of the& Bartletthost, Justicia Learning,. LLC highly modified:© Jones The black-and-white & Bartlett structure Learning, is a massive LLC set of NOT FOR SALE OR DISTRIBUTION fused stamens.NOT FOR SALE OR DISTRIBUTION

Cactus cortex © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Body of Tristerix aphyllus

Cactus phloem © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Cactus xylem NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Cactus pith

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE C The small cluster of cells with large red-stained nuclei are part of the body of Tristerix aphyllus, a holoparasite whose FIGURE D The dark blobs do not belong to the visible shoot; vegetative body grows entirely within the body of its host, in instead, they are the flowers of a holoparasitic plant, Pilostyles this case, the cactus Trichocereus chilensis. The body of T. aphyllus thurberi, growing completely inside its host, the shrub Dalea. © Jones &consists Bartlett of just parenchymaLearning, and LLC lacks leaves, stems, epidermis, © JonesHoloparasites & Bartlett typically Learning,must emerge from LLC underground or from NOT FORand SALE virtually OR all other DISTRIBUTION features of an angiosperm body. NOTinside FOR their SALE hosts when OR they DISTRIBUTION flower. Overview of Plant Metabolism 33

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Sunlight 6CO2 + 6H2OC6H12O6 + 6O2 © Jones & Bartlett Learning, LLC Chlorophyll © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONCarbon dioxide + Water NOTSugar FOR + Oxygen SALE OR DISTRIBUTION Released to atmosphere

Some used by the leaf © Jones & Bartlett Learning, LLC for its own needs © Jones & Bartlett Learning, LLC

NOT FOR SALE OR DISTRIBUTIONMost transported to NOT FOR SALE OR DISTRIBUTION the rest of the plant

FIGURE 2-21 Simple diagram representing the raw materials and products of photosynthesis; carbohydrates produced by photosynthesis are subsequently converted © Jones & Bartlettto many other Learning, compounds. LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Plants obtain the needed water through their roots, and carbon dioxide is absorbed from air through the epidermis. Miner- als are a fourth raw material plants need, and these, too, are © Jones &absorbed Bartlett by roots. Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEPhotosynthesis OR DISTRIBUTION is the central metabolism by which NOT FOR SALE OR DISTRIBUTION plants acquire energy. For the vast majority of plants and algae, there is absolutely no alternative at all. The exceptions are parasitic plants that absorb organic material from a host plant. Plants are green because they contain the pigment chlorophyll, a molecule ©that Jones both captures & Bartlett the energy Learning, of light LLC © Jones & Bartlett Learning, LLC and then passes that energyNOT to otherFOR chemicals, SALE ORtransforming DISTRIBUTION NOT FOR SALE OR DISTRIBUTION them. Through several metabolic steps, the captured light energy forces carbon dioxide to react with water, which yields oxygen and carbohydrate. The oxygen diffuses out of leaves as a waste product; the carbohydrate is used as the starting point FIGURE 2-22 Only the leaves of these palms (Washingtonia for all© metabolic Jones pathways & Bartlett (FIGURE Learning, 2-21). LLC filifera) are green© Jones and photosynthetic; & Bartlett they Learning, are the only parts LLC of PhotosynthesisNOT FOR SALEonly occurs OR when DISTRIBUTION light, chlorophyll, and the trees thatNOT produce FOR sugar. SALE All other ORparts, DISTRIBUTION such as the long carbon dioxide are present. It does not occur at night, in dark stems and the underground root systems, have no chlorophyll caves, deep in the oceans, nor does it occur after a plant has and must obtain all their energy in the form of sugars transported shed its leaves in autumn. Photosynthesis also does not occur downward from the leaves by phloem. in organs such as roots, bark, and flowers that do not have © Jones &chlorophyll Bartlett (FIGURE Learning, 2-22). ConsequentlyLLC the light energy © Jones & Bartlett Learning, LLC NOT FORcaptured SALE by OR photosynthesis DISTRIBUTION must be moved from leaves out toNOT Respiration FOR SALE breaks OR down DISTRIBUTION glucose and transfers its energy other organs that do not photosynthesize, and this transport to ATP. During photosynthesis, light energy is captured as is carried out by phloem. Also energy must be stored from carbon dioxide combines with water, producing oxygen and daytime to night and from summer to winter. Most plants glucose. Respiration is more or less the reverse: Oxygen and store energy by polymerizing glucose molecules together glucose react, producing carbon dioxide and water, with the into starch, which is more© compactJones and & Bartlettstable than Learning,sugar. A LLCenergy being transferred to ATP© rather Jones than & being Bartlett given off Learning, LLC few plants, such as peanuts,NOT sunflower FOR SALE seeds, and OR avocados, DISTRIBUTION as light. NOT FOR SALE OR DISTRIBUTION convert glucose to fats and store those as lipid droplets within Plants also need minerals such as nitrogen, phosphorus, their cells, but plants never have adipose tissue like ours. potassium, iron, and others. Plants use these in much the same Respiration is another type of energy metabolism and way we do; phosphate is needed for ATP; nitrogen becomes part it occurs in all organisms, with no exceptions whatsoever. As of amino acids and nucleic acids; iron is attached to molecules just mentioned,© Jones glucose & Bartlett is used toLearning, store energy LLCand to move that transfer electrons,© Jones and & so Bartlett on. Also like Learning, us, plants are LLCnot energyNOT from FOR organ toSALE organ. ORBut aDISTRIBUTION problem with glucose is especially effectiveNOT atFOR recycling SALE minerals; OR weDISTRIBUTION lose minerals as we that it stores too much energy for certain needs. Cells force sweat, urinate, and defecate. Plants lose minerals has they shed many metabolic pathways to run by adding a small bit of their leaves, withered flowers, and fruit. They pack their seeds energy to two or three steps of the reaction. A molecule with minerals that the seedlings will need, and all those minerals called ATP (adenosine triphosphate) provides just the right are provided by the parent plant. The amount of minerals a plant © Jones &amount Bartlett of energy Learning, for most of LLC the steps (FIGURE 2-23). Glu-© Jonesneeds is & surprisingly Bartlett small; Learning, the ash that LLC remains after a fire con- NOT FORcose SALE has about OR 36 DISTRIBUTION times as much energy as is carried by ATP.NOT tains FOR all the SALE minerals OR that DISTRIBUTION had been present in the wood. 34 Chapter 2: Overview of Plant Life

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Consider two facts: (1) NOTPlants liveFOR among SALE herbivores, OR DISTRIBUTION and power of ATP to pump sodiumNOT and potassium FOR SALE across aOR mem- DISTRIBUTION (2) the world is full of uneaten plants. What is the cause? brane. When this pump is blocked in heart cells, it leads to Many plants produce toxic compounds: Poison ivy, death an increase in the concentration of calcium within the cells. camas, poison hemlock, and deadly nightshade are familiar Although foxglove leaves are injurious if eaten improperly, examples, but the full list of toxic plants is very long. Many these chemicals are used medicinally to slow and strengthen plants© we Jones think of &as Bartlettbeing nonpoisonous Learning, are only LLC harmless heartbeat. © Jones & Bartlett Learning, LLC becauseNOT we stop FOR eating SALE things OR that DISTRIBUTIONare bitter or that burn our CyanogenicNOT glycosides. FOR SALEThese areOR nontoxic DISTRIBUTION in the plant, mouths: Few people would eat enough chili peppers to get a but enzymes in our digestive system cleave them into two lethal dose. The following are some toxins in plants we live parts: a sugar and cyanide. Cyanide inhibits the final step with. Fascinating and well-illustrated accounts of many are in aerobic respiration, preventing generation of ATP. These given in Handbook of Poisonous and Injurious Plants by Lewis toxins are found in some of our most common fruits— © Jones &S. Nelson,Bartlett Richard Learning, D. Shih, and LLC Michael J. Balick (2007, © JonesMalus (apples)& Bartlett and Prunus Learning, (“stone fruits”LLC such as cherries, NOT FORSpringer). SALE OR DISTRIBUTION NOTpeaches, FOR SALEapricots)—but OR DISTRIBUTION in parts that we do not eat such Anticholinergic (antimuscarinic) poisons. Many nerve as apple seeds or peach pits. Poisoning most often occurs cells have receptors that detect the presence of a small mole- when apricot seeds are used as components of herbal cule called acetylcholine, which causes a reaction in the nerve medicines. cells when it binds to the receptors. Plants such as Atropa Mitotic inhibitors. Microtubules create the spindle that (deadly nightshade) and© Datura Jones (jimsonweed) & Bartlett produce Learning, LLCpulls chromosomes to opposite© endsJones of the & cellBartlett during Learning, LLC chemicals that bind to oneNOT of these FOR receptors SALE (called OR DISTRIBUTIONthe mus- nuclear division. The alkaloidNOT colchicine FOR in SALE autumn OR DISTRIBUTION carinic receptor), preventing acetylcholine from stimulating crocus, Colchicum autumnale, prevents the assembly of proper nerve transmission. microtubules. Cells exposed to this poison cannot form a Nicotine-like alkaloids. Alkaloids are small molecules spindle, and division fails. We humans have many tis- that contain nitrogen and somewhat resemble amino acids. sues with rapidly dividing cells, such as the lining of our Alkaloids© Jones of Conium & Bartlett(poison hemlock), Learning, Nicotiana LLC (tobacco), digestive tract,© Jonesbone marrow & Bartlett cells that Learning, produce red LLCblood and SophoraNOT FOR(mescal SALE bean) block OR anotherDISTRIBUTION acetylcholine cells, and seminiferousNOT FOR tubules SALE in men.OR DISTRIBUTIONCatharanthus receptor (this one called the nicotinic subtype). Symptoms roseus (also called Vinca rosea, periwinkle) produces the occur in the parasympathetic and sympathetic parts of the alkaloids vinblastine and vincristine that also block cell nervous system, the brain, and the junctions where nerves division; these are used in chemotherapy to stop cancer attach to muscles. cells from dividing. © Jones & BartlettConvulsant Learning, poisons. The LLC small tree Strychnos produces © JonesToxalbumins. & Bartlett These Learning, proteins bind LLC to ribosomes and NOT FORstrychnine, SALE OR which DISTRIBUTION causes motor nerve cells to be hyperexcit-NOTprevent FOR them SALE from OR translating DISTRIBUTION messenger RNA into protein. able and results in convulsions. Several other plants produce Ricinus (castor bean) produces the toxalbumin ricin, one convulsants. of the most toxic substances known. Jatropha species (coral Capsaicin. Chili peppers such as habaneros, jalapeños, bean) has a higher concentration of a related toxalbumin, and and tabascos in the genus Capsicum contain capsaicin, which a single seed can cause severe poisoning. induces some of our sensory© Jones nerve cells & Bartlett to release aLearning, chem- LLCUrushiol. About half of all© people Jones are &allergic Bartlett to Learning, LLC ical called substance P, whichNOT specifically FOR SALE stimulates OR DISTRIBUTIONother urushiol, an oily substance in NOTspecies FOR of Toxicodendron SALE OR DISTRIBUTION nerve cells that normally respond when we are being burned. (poison ivy [FIGURE A], poison oak, and poison sumac). Artificial selection by humans has resulted in chili peppers All parts of these plants can trigger an allergic reaction that range from having almost no capsaicin (bell peppers) (FIGURE B). to some that are dangerous (cayenne, chiltepin, and Thai). Remember that these plants do not have toxic com- Capsaicin© Jones is hydrophobic, & Bartlett so drinking Learning, water will LLC not cool pounds in order© Jones to protect & themselves,Bartlett Learning,or with the purpose LLC your NOTmouth; FOR however, SALE the fat OR in cheese, DISTRIBUTION butter, and milk will of keeping herbivoresNOT FOR away. SALE It is just OR that DISTRIBUTIONtoxic or injurious absorb it and give some relief. plants are more likely to be left uneaten compared with non- Cardioactive compounds. Digitoxin and digoxin in toxic plants and therefore are more likely to produce more Digitalis (foxglove) inhibit a set of proteins that use the seeds and more progeny.

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FIGURE A Each leaf of poison ivy has three leaflets and the FIGURE B This is the initial, mild reaction of a cautious, light defensive compound urushiol. brush with stinging nettle (Urtica dioica), just to see the effect. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

TABLE 2-3 Chemicals That Plants Produce Starting NH2 with Glucose © Jones & Bartlett Learning, LLC C N © JonesChemicals & Bartlett All sugars Learning, LLC N C NOT FOR SALE OR DISTRIBUTION CH NOT thatFOR contain SALE OR DISTRIBUTION Adenine Carbohydrates HC C no minerals O– O– O– NN Lipids – O ~~OP OP OP CH2 O Waxes O O O HHH © JonesHH & Bartlett Learning, LLC Most pigments© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION OH OH Many vitamins

Chemicals Amino acids Adenosine that contain Nucleic acids Adenosine monophosphate nitrogen © Jones & Bartlett Learning, LLC © JonesSome hormones & Bartlett Learning, LLC NOT FOR AdenosineSALE OR diphosphate DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Some pigments Adenosine triphosphate Chemicals Some amino acids contain sulfur. that contain Chlorophyll contains magnesium. various FIGURE 2-23 Adenosine triphosphate. Breaking off the last © Jones & Bartlett Learning, LLC © Jonesminerals & Bartlett Learning, LLC phosphate (on the left) to produce adenosine diphosphate (ADP) Cytochromes that carry electrons contain iron. NOT FORresults SALE in a moreOR stableDISTRIBUTION set of electron orbitals, and energy is NOT FOR SALE OR DISTRIBUTION ATP contains phosphorus. given off. The same is true of removing the second phosphate, but not the third. Calcium pectate is the glue that binds each cell to its neighboring cells.

Plants are master chemists.© Jones Starting & Bartlett with just glucose,Learning, LLCNote: All chemicals in a plant are produced© Jones with glucose & Bartlett as a starting Learning, LLC point. Even fragrances and nectars that are released from the plant minerals, and water, theyNOT synthesize FOR every SALE single OR molecule DISTRIBUTION are synthesized from glucose. Only NOTthe most FOR familiar SALEchemicals ORare DISTRIBUTION they need for all aspects of their life (TABLE 2-3). They listed here. synthesize all amino acids, nucleic acid, and fatty acids; they make all the pigments of flowers and fruits; they make waxes, oils, resins, and fragrances. And poisons—many plants© defend Jones themselves & Bartlett from pests Learning, with an amazing LLC array ❚ © Jones & Bartlett Learning, LLC of poisons.NOT SomeFOR are SALE bitter or OR irritating, DISTRIBUTION others kill animals ❚ OvervieNOT FORw of SALE Information OR DISTRIBUTION quickly; some of the most toxic chemicals interfere with cells in Plants in the brain and nervous system. Although we humans need a complex diet that includes several amino acids, fatty acids, A universal feature of all known life on Earth is that DNA and vitamins that we cannot make for ourselves, that is never (deoxyribonucleic acid) is used to store information. Just as © Jones &true Bartlett of plants. Learning,Their balanced LLC diet is sunlight, carbon dioxide,© Joneswith energy & Bartlett and matter, Learning, organisms take LLC in information, store NOT FORwater, SALE and ORminerals. DISTRIBUTION NOTit, FOR move itSALE from place OR to DISTRIBUTION place, transform it, use it, and then 36 Chapter 2: Overview of Plant Life

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pass it onto their offspring when they reproduce. The greatest source of information for any individual is its parents: the © Jones DNA& Bartlett contained Learning, in the sperm LLCcell and egg cell that initiated © Jones & Bartlett Learning, LLC NOT FORthe SALE life of the OR individual. DISTRIBUTION In plants, DNA is stored in the NOT FOR SALE OR DISTRIBUTION nucleus of each cell, as well as in plastids and mitochon- dria, which are also present in all living plant cells. When a cell needs to use some of the information, it transforms the needed information by making messenger RNA (ribonucleic acid), and then it transfers© Jonesthat information & Bartlett to the areaLearning, of the LLC © Jones & Bartlett Learning, LLC cell where it is needed. MostNOT of FORthe information SALE OR is further DISTRIBUTION NOT FOR SALE OR DISTRIBUTION transformed as the messenger RNA guides the production of specific proteins. Smaller pieces of RNA, often called microRNA, act by binding to various components of the cell, activating some, inhibiting others, and in general fine- tuning© the Jones activities & of Bartlett many genes. Learning, The DNA ofLLC each species FIGURE 2-24© AllJones plants here & Bartlett obtain energy Learning, from their LLC is unique;NOT for FOR example, SALE cherries OR (Prunus DISTRIBUTION avium) and peaches environment,NOT but think FOR of the SALE two trees. OR They DISTRIBUTION both obtain (Prunus persica) have almost identical DNA, but the infor- information about which way is up (the opposite direction of the mation in several genes in one differs just enough from that force of gravity pulling on all parts). For the grasses in the pasture, of the other so that cherries are small, red, and shiny, whereas up is in the direction of the brightest light, but for the tree on peaches are large, yellow, and fuzzy, and each has distinct the right (closer to the shed), the brightest light is away from © Jones &flavors Bartlett and aromas. Learning, LLC © Jonesthe larger & treeBartlett that is shading Learning, it, so “bright” LLC and “up” are not the A plant, just like any other organism, also uses infor- same thing for it. These trees also need to detect the approach of NOT FOR SALE OR DISTRIBUTION NOTwinter FOR and SALE abscise ORtheir leavesDISTRIBUTION while they can, and they probably mation from the environment. Environmental information detect the presence of many insects and fungi as well. must be perceived then transferred to where it is needed, and finally the plant must respond appropriately. While the plant is still nothing more than a dormant seed, the environmental information it responds© to Jonesis often very& Bartlett simple: It is Learning, warm LLC © Jones & Bartlett Learning, LLC enough to germinate. AsNOT temperatures FOR SALE climb from OR winter DISTRIBUTION to NOT FOR SALE OR DISTRIBUTION springtime, at some point they are warm enough, and many seeds then respond by becoming active, respiring more rapidly, and germinating. Seeds of other species remain dormant because they are dry, not cold; they need to detect when their surroundings© Jones have & become Bartlett wet enough Learning, to support LLC a growing © Jones & Bartlett Learning, LLC seedling.NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The environment also supplies a large amount of more complex information, in many forms (FIGURE 2-24). Sun- light provides the energy for photosynthesis, of course, and it also indicates the direction up (the direction of brighter © Jones &light) Bartlett from down Learning, (the direction LLC of less light and more © Jones & Bartlett Learning, LLC NOT FORshade). SALE In ORall parts DISTRIBUTION of the world except near the equator, NOT FOR SALE OR DISTRIBUTION sunlight provides information about seasons: Days are shorter in winter, longer in summer. By detecting this, a FIGURE 2-25 When these bulbs became active and started plant measures the season and responds by flowering and growing, all parts were so deeply buried in soil that they could fruiting at the correct time and by becoming dormant in not detect any sunlight. But both new roots and new leaves autumn. Roots are not exposed© Jones to sunlight, & Bartlett but they Learning, detect detectLLC gravity, with roots growing© downward, Jones leaves& Bartlett growing Learning, LLC gravity and thus know whichNOT direction FOR SALE is down. OR Deeply DISTRIBUTION upward. NOT FOR SALE OR DISTRIBUTION buried bulbs also detect gravity and respond in two opposite ways: Roots follow gravity downward, whereas shoots grow upward (FIGURE 2-25). We are now learning that some A large amount of hormone indicates the leaves are active plants are much more perceptive than we ever suspected. and need water. The roots respond by growing and absorb- Tendrils© Jones bend toward & Bartlett anything thatLearning, gives them LLC even the ing water and© nutrients.Jones &In Bartlettautumn, as Learning,leaves prepare LLC to be slightestNOT touch, FOR leaves SALE detect OR the growthDISTRIBUTION of a single fungus shed, they stopNOT producing FOR SALEthe hormone, OR DISTRIBUTION so the amount of spore on their surface, and some orchids detect whether a the hormone decreases, indicating the leaves no longer need pollinator has merely landed on one of their flowers or if it water. Roots respond by slowing their growth and conserv- has actually taken the pollen. ing their energy. After a flower is pollinated, the developing Various parts of a plant itself create information that fruit sends signals indicating that it needs nutrients for © Jones &informs Bartlett the rest Learning, of the plant LLCof their activities. Healthy © Jonesitself and & theBartlett embryonic Learning, seeds inside. LLC This communica- NOT FORleaves SALE produce OR hormonesDISTRIBUTION that are carried to the roots: NOTtion FOR among SALE the parts OR of DISTRIBUTION a plant is necessary to keep the Overview of Information in Plants 37

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plant integrated and all parts developing in coordination. of them will be given here. Definitions of important terms are It is especially remarkable considering the long distances grouped together in TABLE 2-5. © Jones involved& Bartlett between Learning, the thousands LLC of leaves, flowers, branches,© JonesMosses, & Bartlett liverworts, Learning, and hornworts LLC are often grouped NOT FORand SALE roots ofOR a large DISTRIBUTION tree. NOTtogether FOR andSALE called OR bryophytes DISTRIBUTION (pronounced BRY oh fights) (FIGURES 2-26 to 2-29). They are similar to each other because they not only lack vascular tissues and seeds, but also because plants in all three groups are haploid. Mosses, liver- ❚❚ Overview of Plant worts, and hornworts are unique among plants because they Diversity and© Jones Evolution & Bartlett Learning, LLClive their lives with only one set© of Joneschromosomes, & Bartlett not two. Learning, LLC NOT FOR SALE OR DISTRIBUTIONTheir bodies are very simple, notNOT much FOR more SALEcomplex OR than DISTRIBUTION All the thousands of species of plants of the world are not the algae that were the ancestors of plants. just a hodgepodge of randomly associated features. Instead All other groups of plants have vascular tissue and are there are several large, recognizable groups such as mosses, diploid. Many vascular plants resemble bryophytes in being ferns, conifers, and angiosperms. Within each group, we are unable to form seeds; they reproduce using spores and are typ- likely ©to findJones certain & Bartlettfeatures and Learning, unlikely to find LLC others. For ically called the© Jonesspore-bearing & Bartlett plants. These Learning, are often LLCreferred example,NOT mosses FOR never SALE have xylemOR DISTRIBUTION or phloem and they never to as ferns andNOT the “fern FOR allies” SALE (FIGURES OR DISTRIBUTION2-30 to 2-32). have seeds either. As a second example, ferns always have An old way of thinking about plants is that ferns and vascular tissue but they never reproduce with seeds. Several “fern allies” had advanced above the bryophytes as they aspects of the groups in TABLE 2-4 are not quite accurate, evolved to have vascular tissue, but then their evolution “stag- but the groups and terms presented there have been used for nated” while other vascular plants continued to advance evo- © Jones &more Bartlett than 100 years, Learning, and you LLC will still encounter them often© Joneslutionarily & Bartlett to the point Learning, where they could LLC make seeds as well as NOT FORin SALE books about OR gardeningDISTRIBUTION and roadside flowers. An overviewNOT vascular FOR tissues.SALE The OR moreDISTRIBUTION advanced seed plants then divided

TABLE 2-4 Overview of the Main Clades of Organisms

Archaea © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Bacteria NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Eukarya Animals

Fungi

Plants (also Plants without Mosses called true vascular tissue © Jones & Bartlett Learning, LLC plants, land © Jones &Liverworts Bartlett Learning, LLC plants, or em- Hornworts NOT FOR SALE OR DISTRIBUTIONbryophytes) NOT FOR SALE OR DISTRIBUTION Plants with Plants without Lycophytes vascular tissues seeds (vascular (often called (vascular cryptogams) “fern allies”) plants) © Jones & Bartlett Learning, LLC Ferns © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONPlants with CycadsNOT FOR SALE OR DISTRIBUTION seeds (spermatophytes) Ginkgo Gnetophytes

NOT FOR SALE OR DISTRIBUTION NOT FORAngiosperms SALE OR DISTRIBUTION Basal angiosperms (several groups)

Monocots © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Eudicots NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 38 Chapter 2: Overview of Plant Life

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TABLE 2-5 Terms Used for Plant Groups* © Jones &Thallophytes Bartlett andLearning, A thallus LLC (plural, thalli; pronounced THAL© eye)Jones is a body & Bartlett that is not composed Learning, of roots, LLC stems, and leaves, NOT FOR CormophytesSALE OR DISTRIBUTIONand which does not have typical plant tissues.NOT TheFOR only SALE plants that OR are DISTRIBUTION thallophytes are hornworts and the “thalloid” liverworts (liverworts without stems and leaves). Many algae are unicellular, but in those that have a multicellular body, the body is called a thallus. For example, the body of a kelp is a thallus. The bodies of fungi (mushrooms, puffballs, brackets) and lichens are also called thalli. The term is never used for animals. All plants that are not thallophytes are cormophytes, plants whose body consists of at least stems (the earliest plants lacked leaves and roots). The term “cormophyte” is rarely used because virtually all plants are cormophytes,© Jones &and Bartlett we simply Learning,say “plant.” The bodyLLC of a cormophyte is just a “body,”© Jones it is not “corm” & Bartlett (“corm” Learning, LLC refersNOT to FOR modified SALE subterranean, OR DISTRIBUTION vertical stems with papery leaves, as in GladiolusNOT). FOR SALE OR DISTRIBUTION Many algae are unicellular; that means their body consists of just one cell. This never occurs in plants: All plants have multicellular bodies, there are no exceptions.

Nonvascular and Plants that lack vascular tissues are nonvascular plants. The only ones are mosses, liverworts, and horn- vascular© Jones plants & Bartlettworts. All otherLearning, plants have LLC vascular tissues and so are vascular© Jones plants, also& Bartlett known as tracheophytesLearning, .LLC Spore-bearingNOT FOR and SALEWe need OR to DISTRIBUTIONbe careful here because popular books and manyNOT biology FOR texts SALE are misleading OR DISTRIBUTION about spore- seed plants bearing plants. All plants produce spores; there are no exceptions. The term “spore-bearing plant” usually refers to those plants that never make seeds, which are mosses, liverworts, hornworts, lycophytes, and ferns. All other plants make seeds as well as spores. A common term for “spore-bearing plant” is cryptogam: Before the invention of lenses, spores could not be seen, so botanists thought that ferns and the others had “hidden © Jones & Bartlett Learning,seeds” LLC (crypto = hidden; gam = seed). Ferns© Jones and lycophytes & Bartlett have vascular Learning, tissue but LLC no seeds, so they are vascular cryptogams, whereas mosses, liverworts, and hornworts are nonvascular cryptogams. NOT FOR SALE OR DISTRIBUTIONWhereas all plants produce spores, onlyNOT seed FOR plants SALEproduce seeds,OR DISTRIBUTION and a technical term for them is spermatophytes. All seed plants are vascular plants, with no exceptions, so it is not necessary to say “vascular seed plants” or “vascular spermatophytes.”

Gymnosperms Until just a few years ago, all seed plants that did not produce flowers were grouped together as “gymno- (cone-bearing sperms,”© Jones which & included Bartlett cycads, Learning, Gnetales (sometimes LLC called gnetophytes),† ginkgos,© Jones and conifers. & Bartlett But new Learning, LLC seed plants) and evidenceNOT FOR is interpreted SALE as OR showing DISTRIBUTION that angiosperms have the same ancestor NOTas these FOR groups SALE (they all ORshare DISTRIBUTION angiosperms a common ancestor), so all seed plants should either be grouped together, or each group should be kept (flower-bearing separate: It is incorrect to include some groups (“gymnosperms”) and leave out others (angiosperms). At plants) present, we use the general term “seed plant” to refer to all of them, or we refer to each small group individu- ally. The term “gymnosperm” should not be used, but you will still see it even in modern books and papers. The term “angiosperm” is derived from the formal name for flowering plants, Angiospermae in older classi- © Jones & Bartlettfications, Learning,Magnoliophyta LLC or Angiospermophyta in most modern© Jones treatments. & Bartlett Many authors, Learning, even in technical LLC NOT FOR SALEjournals, OR use DISTRIBUTION the term “flowering plants” rather than “angiosperms.”NOT FOR SALE OR DISTRIBUTION Basal As explained in the text, until recently all angiosperms were classified as either monocots (“monocotyledons” angiosperms, is a longer, older name) or dicots (dicotyledons), but now we realize some of the species we had classified as monocots, and dicots had become evolutionarily distinct very early in angiosperm history, so now we refer to those as basal eudicots angiosperms; examples are Amborella trichopoda (the most basal of all known living flowering plants), water © Jones & Bartlett Learning,lilies, MagnoliaLLC and its relatives, and a few© others).Jones The & old Bartlett term “dicot” Learning, had to be abandoned, LLC and a new NOT FOR SALE OR DISTRIBUTIONterm, “eudicot,” refers to “all the dicots minusNOT the FOR basal angiosperms.”SALE OR Most DISTRIBUTION basal angiosperms resemble eudicots very strongly; their leaves are similar (broad and with a petiole, not long and strap-shaped like leaves of monocots), as is the arrangement of vascular bundles in their stems and many other features. Therefore, it is still common to see people refer to “dicot leaves” rather than “basal angiosperm and eudicot leaves.”

Lower plants and These are completely nontechnical terms and have no set definition. All people would consider seed plants higher plants to© be Jones among the& “higherBartlett plants” Learning, and cryptogams LLC to be “lower plants,” but it is often© Jones difficult & to Bartlett be certain Learning, LLC exactlyNOT whatFOR an SALEauthor means OR whenDISTRIBUTION these terms are used. These terms designateNOT grades, FOR a system SALE no longerOR DISTRIBUTION used, and these two terms should not be used any longer.

* Several informal terms are used for various plant groups. You will encounter many of these in books and articles about plants. † Names in formal classifications are capitalized but informal names are not. The informal names of some of the groups here are: angiosperms, conifers, gnetophytes, and mosses. Their formal names are: Angiospermophyta, Coniferophyta, Gnetales (some people use Gnetophyta), and Musci (an© Jones old name & for Bartlettmosses) or Bry Learning,ophyta (a newer LLC name for mosses). © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

into two groups, those with naked seeds (the gymnosperms) a pine cone is extremely young; at that point, its scales are and those with “clothed seeds” (the angiosperms, often far enough apart that you can look in and see the individual called the flowering plants). Here, “clothed seeds” refers to naked ovules. The carpels of angiosperms are always sealed, © Jones &seeds Bartlett formed insideLearning, a fruit in LLC contrast to naked seeds that are© Jonesand the & ovules Bartlett are never Learning, visible without LLC cutting the young NOT FORproduced SALE inOR a cone. DISTRIBUTION The term “naked” refers to the time whenNOT fruit FOR open. SALE There ORare other DISTRIBUTION differences between gymnosperms Overview of Plant Diversity and Evolution 39

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FIGURE© Jones2-26 Mosses & Bartlett cover the rocksLearning, in this stream LLC in the FIGURE 2-28© ThisJones is a rather & Bartlett common thalloid Learning, liverwort LLC OlympicNOT National FOR Park. SALE Mosses ORhave DISTRIBUTIONno xylem or phloem and (ConocephalumNOT conicum FOR) that SALE is easy to OR recognize: DISTRIBUTION Its bodies cannot conduct water very well, so they are typically very small never have any hint of leaves or stems, they are flat and about plants. Although we associate mosses with damp places, many 1 cm wide, and they occasionally fork into two growing points. are adapted to deserts, being inactive except on rare days when it Their upper surface has a distinctive diamond-like pattern that there is rain, fog, or dew. resembles reptile skin. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 2-29 Hornworts such as this Phaeoceros laevis are widespread, but they only thrive when it has been rainy for FIGURE 2-27 These are plants of the leafy liverwort Bazzania © Jones & Bartlett Learning, LLC © Jonesawhile; &they Bartlett grow in shady Learning, places, sometimes LLC on bare soil, trilobata. As with mosses, the bodies of leafy liverworts consist sometimes mixed among grasses. Each long projecting cylinder NOT FORof SALE a stem and OR leaves, DISTRIBUTION but never any roots, xylem, or phloem. It NOT(about FOR 1 cmSALE long) isOR the “horn”DISTRIBUTION and is actually the diploid portion is usually necessary to have a hand lens or magnifying glass to of the plant (technically, a sporophyte): Each horn is the same distinguish between a leafy liverwort and a moss. phase of the life cycle as is a tree, bush, shrub, or any other familiar plant. The small flat patches of tissue in contact with the soil are the gametophytes, the haploid part of each plant: It is and angiosperms that make© Jones us think &of angiospermsBartlett Learning, as being theLLC part that is similar to mosses, ©leafy Jones liverworts, & Bartlettand thalloid Learning, LLC more advanced: AngiospermsNOT haveFOR more SALE complex OR wood DISTRIBUTION and liverworts. The life cycle of plantsNOT is much FOR more complexSALE than OR DISTRIBUTION leaves, as well as several modifications that improve photosyn- that of animals, but is fascinating. thesis. Angiosperms also cooperate with animals that pollinate their flowers and distribute their seeds, whereas conifers than all the rest, to the point of having flowers and fruits. never rely on animals for pollination, and only a few cooper- Some would even refer to angiosperms as the “pinnacle” of ate with© Jonesanimals for & seedBartlett dispersal. Learning, LLC plant evolution.© Jones In this method,& Bartlett emphasis Learning, is placed on LLC the WeNOT can FORarrange SALE the different OR DISTRIBUTION groups in a linear level to whichNOT a group FOR has SALE evolved. OR The DISTRIBUTIONtechnical word for sequence that seems to reflect plant evolution. The earliest level is grade; we are grouping plants into grades, with the true plants were more advanced than algae because they lowest grade being nonvascular plants, the highest grade had simple tissues and organs but little else. This would be being angiosperms. We still encounter this concept of grade the moss level of evolution. Other plants advanced to the when people refer to the “lower plants” and “higher plants.” © Jones &level Bartlett of having Learning, vascular tissues; LLC others continued evolving © JonesThis grouping & Bartlett by grade Learning, is very handy LLC if you are not too wor- NOT FORto SALE the point OR of havingDISTRIBUTION seeds. Then one group evolved moreNOT ried FOR about SALE accuracy, OR but DISTRIBUTION we now have a newer method of 40 Chapter 2: Overview of Plant Life

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A © Jones & Bartlett Learning, LLC B © Jones & Bartlett Learning, LLC FIGURENOT 2-30 FOR (A) This SALE Selaginella OR lepidophylla DISTRIBUTION is used as an example of a “fern ally” NOTbecause FOR of its interesting SALE OR biology: DISTRIBUTION It is a resurrection plant. It is a diploid vascular plant with xylem and phloem, and it grows in harsh deserts with long dry periods. This photograph shows the plant after autumn rains, when the plant is hydrated, healthy, and active. Compare with Figure 2-30B. (B) This is also Selaginella lepidophylla but after a long dry period; the plant has curled up, minimizing the amount of surface exposed to dry air and UV light. Although it looks dead, it is not only alive but very healthy, merely dormant, somewhat like a dry seed that is alive. After a rain, these © Jones &plants Bartlett would uncurl Learning, and look like LLC those in Figure 2-30A. If forcibly© uncurledJones now, & Bartlett the inner parts Learning, would be bright LLC green. Although called resurrection plants, they do not really return from the dead. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 2-31 These plants of Equisetum telmateia are diploid FIGURE 2-32 This is a single plant of sword fern (Polystichum © Jones &vascular Bartlett plants Learning,that are now considered LLC to be part of the ferns. © Jonesmunitum &); itBartlett has a short Learning,vertical stem that LLC supports the many leaves, NOT FORThese SALE are descendants OR DISTRIBUTION of an ancient group: Fossils of plants thatNOT and FOR below SALE ground areOR many DISTRIBUTION fibrous roots. Ferns are diploid and have similar features can be found in rocks as much as 150 million have xylem and phloem, but their spores grow into tiny haploid years old. Equisetums are called horsetails or scouring rushes, plants that resemble the bases of hornworts (Figure 2-29). This and are distinctive in having a very coarse surface (due to having large sword fern pictured here is the equivalent of a hornwort horn silica in their cell walls); they can be found almost everywhere, (both are sporophytes). In rainy areas of the Pacific Coast of the particularly along streams and along railroad tracks in moist © Jones & Bartlett Learning, UnitedLLC States, sword ferns are so abundant© Jones they &resemble Bartlett meadows Learning, LLC areas. of grass; indeed, millions of years ago before grasses evolved, NOT FOR SALE OR DISTRIBUTIONmost “grasslands” were actually hugeNOT patches FOR of ferns. SALE Ferns ORand DISTRIBUTION dinosaurs were abundant at the same time, long before grasslands grouping plants, one based on groups that consist of all the existed—the herbivorous dinosaurs ate ferns and “fern allies.” species that evolved from a common ancestor. Such a group is a clade. Fortunately,© Jones grouping& Bartlett plants Learning, into clades gives LLC us almost into cycads, ©others Jones became & ginkgos,Bartlett another Learning, group evolved LLC the sameNOT result FOR as grouping SALE them OR into DISTRIBUTION grades (FIGURE 2-33). into conifers,NOT and still FOR another SALE group OR became DISTRIBUTION angiosperms. We need to abandon only a few of the old terms. For exam- There are two important points here. The first is that a ple, we no longer use the term “gymnosperm.” We suspect— clade consists of an ancestor and all its descendants, so the but are not at all certain—that seeds evolved only once. group “seed plants” is acceptable—it is a clade. But the word If so, then all seed plants alive today descended from that “gymnosperms” refers to all seed plants except angiosperms; © Jones &original Bartlett species Learning, of seed plant, LLC and we say it was the common© Jonesit includes & Bartlett the common Learning, ancestor of seedLLC plants but only NOT FORancestor SALE toOR all seedDISTRIBUTION plants. Some of its descendants evolvedNOT some, FOR not SALE all descendants, OR DISTRIBUTION so “gymnosperms” is not a clade. Overview of Plant Diversity and Evolution 41

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Vascular plants plant that made flowers but not cones. At present, we are able to analyze the sequence of nucleotides in the genes of Seed plants © Jones & Bartlett Learning, LLC © Jonesorganisms & Bartlett (we say that Learning, “we sequence LLC their genes”), and we NOT FOR SALE OR DISTRIBUTION NOThave FOR sequenced SALE all OR the DISTRIBUTIONgenes (the entire genome) of many Cryptogams “Gymnosperms” Angiosperms species. This provides an abundance of new information for constructing and testing our theories and models. The old concept of grades assumed that cycads, ginkgos, BOX 2-4 Noah’s Flood and Population Biology orts s

nw and conifers were evolving more slowly than angiosperms cads rn cophytes © Jones & Bartlett Learning, LLCand, given enough time, they would© Jones finally &at longBartlett last evolve Learning, LLC Liverworts Mosses Hor Ly Fe Cy Gnetophytes Ginkgo Conifers Basal angiosperms Monocots Eudicots NOT FOR SALE OR DISTRIBUTIONup to the level of having flowers.NOT Similarly, FOR maybeSALE one ORday inDISTRIBUTION the future, ferns would evolve to the point of having seeds, H and so on. It is like moving from grade to grade in school: Origin of Everyone starts out in the first grade and then all move along flowers G toward graduation, some moving faster than others, some © Jones & Bartlett Learning,Origin LLC of seeds stopping completely.© Jones This & is Bartlettthe second Learning,problem with LLCgroup- (once? twice?) NOT FOR SALE OR DISTRIBUTIONF ing plants intoNOT grades: FOR It assumes SALE that OR all plantsDISTRIBUTION have the same E goal, that having vascular tissue and seeds and flowers is the D optimum way a plant can be adapted to its environment. We C B no longer believe this. A We now realize that there are multiple ways for an organ- © Jones & Bartlett Learning, LLC © Jonesism to be& adaptedBartlett to its Learning, environment. LLC This is reflected in the NOT FOR SALE OR DISTRIBUTION NOTquestions FOR SALE “What areOR the DISTRIBUTION alternatives?” and “What are the con- FIGURE 2-33 This cladogram is a hypothesis about the ways sequences?” Consider mosses and angiosperms, two groups in which modern plants are related to each other. At the very at the opposite end of the old grade system. Mosses are tiny base (marked by A) would be the ancestral plants, not much different from algae. Many years later, at B, some plants began and simple, whereas most angiosperms are large and complex. to evolve into liverworts while the rest of the plants continued But mosses are very well-adapted to their environment: They evolving other features. At© C, Jones some plants & Bartlettbegan to evolve Learning, into LLCthrive in low light, on brick walls© orJones bare stone; & Bartlett they need onlyLearning, LLC mosses, and so on. At someNOT point FOR between SALE D and E,OR vascular DISTRIBUTION enough sunlight, water, and mineralNOT nutrients FOR SALE to make ORa few DISTRIBUTION tissue evolved in the main group of plants, and all plants that spores and then they can reproduce. In the moss clade, evolu- descended from these early vascular plants still have vascular tion by natural selection has found solutions to survival that tissue as well. That means that the xylem in ferns resembles the work well for small, simple plants. Having vascular tissue and xylem in flowering plants not by accident but because both seeds and so on would not make a moss any more adapted evolved© fromJones the same & Bartlett ancestral xylem Learning, (to be really LLC careful: than it is without© Jones them. This & Bartlett is a crucial Learning, point I will empha LLC- The genesNOT that FOR control SALE the development OR DISTRIBUTION of xylem in ferns and size many times:NOT There FOR are SALEmany diverse OR DISTRIBUTIONways to be adapted, the genes that control the development of xylem in flowering numerous ways of thriving. There is not one single structure plants resemble each other because both sets of modern genes evolved from the same set of ancestral genes). The lines that or physiology that will be optimum for every organism. No show the ancestry of cycads, gnetophytes, Ginkgo, and conifers organism is a pinnacle of evolution. all start from the same point (G): That means we do not yet know Botanists are working harder than ever trying to fig- © Jones &which Bartlett diverged Learning, earliest, and we LLC do not know which group is © Jonesure out & how Bartlett plants are Learning, related, which LLC clades are valid. The NOT FORmost SALE closely OR related DISTRIBUTION to which other group. Putting the basal NOTfollowing FOR SALE are the ORones DISTRIBUTION you should know as you continue angiosperm at H is a rather new discovery; we used to think they into this text. Plants are a clade: True plants originated were together with the eudicots. from green algae only once. The technical name for plants, to distinguish them from algae, is embryophytes, We prefer to not to use the term “gymnosperm” if we care but this is used in only the most technical writing. It had about being accurate. © Jones & Bartlett Learning, beenLLC suspected that mosses, liverworts,© Jones and & Bartletthornworts Learning, LLC The second importantNOT point FOR is that SALE the ancestors OR DISTRIBUTION of any might have had a completely separateNOT FOR origin, SALE that perhaps OR DISTRIBUTION clade of living organisms all lived in the past, and for clades they did not descend from the same ancestor that pro- such as angiosperms or conifers or seed plants, the ancestors duced all the other plants. But the sequences of nucleo- lived in the very distant past. Consequently, we can never tides in the genes of bryophytes are so similar to those of be completely certain which ancient, extinct group was the all other plants that we are now confident they, too, are common© Jones ancestor & of Bartlett any modern Learning, clade; instead LLC we have to true plants. ©The Jones terms “vascular & Bartlett cryptogams” Learning, and “fernLLC studyNOT the living FOR organisms SALE and OR try DISTRIBUTION to infer the features the allies” are handyNOT but FOR not accurate.SALE OR Early DISTRIBUTION diploid plants common ancestor had. Using angiosperms as an example, all diverged into two clades, both with vascular tissue and modern as well as fossil angiosperms have vascular tissues; without seeds. One clade, which we call the lycophyte they produce flowers and they make seeds; they never make clade (pronounced LIE co fight), was very successful anything similar to a pine cone; and they are never haploid initially and evolved to be large trees with many complex © Jones &like Bartlett bryophytes. Learning, From this we LLC assume that the common © Jonesfeatures, & butBartlett almost allLearning, became extinct. LLC At present, the NOT FORancestor SALE of OR all flowering DISTRIBUTION plants was a diploid vascular seedNOT surviving FOR SALE descendants OR DISTRIBUTION are Lycopodium, Selaginella, and a 42 Chapter 2: Overview of Plant Life

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The biblical story of Noah’sNOT flood FOR in SALEGenesis providedOR DISTRIBUTION a Could just 12 cattle (clean) breedNOT rapidly FOR enough SALE to ORpro- DISTRIBUTION powerful stimulus for developing the sciences of popula- duce all the herds and wild cattle on Earth in 1700 ad? Could tion biology, biogeography, and evolution. Various biblical just two pigs (unclean) be the source of all swine now present? scholars had studied Old Testament texts, the Jewish Torah, The first step in answering this was to determine the fecundity of and archaeological© Jones & evidence, Bartlett trying Learning, to establish LLCdates such as animals: How© old Jones do they have& Bartlett to be before Learning, they produce LLC their the birth of Jesus (1 ad, which is 2,020 years ago now) and the first young? How many young do they produce in each litter? constructionNOT FOR of Solomon’s SALE temple OR (832DISTRIBUTION bce). Although there is How many surviveNOT long FOR enough SALE to breed? OR And DISTRIBUTION how many sets no archaeological evidence, various Bible scholars concluded of offspring do they produce in their lifetime? Fortunately it was that the flood of Noah occurred in 2348 bce. Noah’s flood about this time that wealthy landowners began keeping track of was of special interest to early scientists because at that point these sorts of numbers for cattle, poultry, fish, fowl, and even the © Jones &according Bartlett to the Learning, Bible, all life LLCon Earth had been destroyed © Jonesdeer in &their Bartlett private forests. Learning, The answer LLC for every type of animal by God except for the creatures in the Ark. Scientists formu- was the same: Yes, all animals produce young rapidly enough to NOT FORlated SALE the question OR DISTRIBUTION “Do plants and animals reproduce rapidlyNOT repopulate FOR SALE Earth in OR much DISTRIBUTION less than 4,000 years. enough to repopulate a completely denuded Earth in the time The early scientists then began to refine their thoughts since Noah?” Thus a scientist posing this question in 1700 ad, and reformulate the question. At present we believe in a “bal- for example, could assume that Earth had been repopulated in ance of nature”: Plants capture carbon and energy through 2,348 + 1,700 = 4,048 years.© Jones & Bartlett Learning, LLCphotosynthesis, then the plants© are Jones consumed & byBartlett herbivorous Learning, LLC First consider the Bible passages that the scientists relied animals or by pathogenic fungi and bacteria. The herbivores on. Genesis 7:2–3 states NOTthat God FOR told SALENoah to takeOR seven DISTRIBUTION are eaten by carnivores. If thereNOT are too FOR many herbivores,SALE OR they DISTRIBUTION pairs of every kind of “clean animal” (those that could be damage the plants too much, and some herbivores starve, used for sacrifice; Genesis 8:20); only one pair of every kind which, in turn, affects carnivores. An outbreak of a patho- of “unclean animal” (which could not be used for sacrifice); genic fungus that damages plants will cause various animals and also© Jonesseven pairs & ofBartlett every kind Learning, of bird. Genesis LLC 7:20 states to starve, and© so Jones on. The &balance Bartlett between Learning, all these factors LLC that the flood completely covered the tops of all mountains; changes from year to year, so the relative numbers of organ- that meansNOT that FOR there SALE was no ORdry place DISTRIBUTION anywhere that animals isms also changeNOT yearly. FOR But SALE prior to ORthe analysis DISTRIBUTION of Noah’s could use as a refuge and survive. Although we are all familiar flood, people believed that a different kind of “balance of with the rain lasting 40 days and 40 nights, the Bible states nature” was maintained by God: God had created the various that it took a long time for the waters to drain away after the carnivores, herbivores, and plants such that plants would rain stopped. For the early scientists the critical passages prosper just enough to supply the herbivores with exactly the © Jones &are Bartlett Genesis 8:4 Learning, and 5 that state LLC that the Ark was floating for © Jonesright amount & Bartlett of food, Learning,and likewise the LLC number of herbivores NOT FOR7 SALEmonths beforeOR DISTRIBUTION it settled on Mount Ararat, and it was 10 NOTwould FOR be SALE perfectly OR correct DISTRIBUTION for the numbers of carnivores in months before the tops of other mountains were visible and the world. The balance would be perfect, never changing, and Noah opened the doors. Especially important was the explicit with no waste or shortage unless God specifically causes a statement that God’s plan succeeded: Genesis 7:23 states that drought or pestilence. everything outside the Ark had been killed. As early scientists studied animal fecundity, they real- In the book of Genesis,© Jones God had & set Bartlett up the perfect Learning, izedLLC that the numbers did not fit© togetherJones to & makeBartlett a divinely Learning, LLC experiment in populationNOT biology. FOR All SALE animals ORhad beenDISTRIBUTION balanced system. All organismsNOT are too FOR fertile. SALE If the previous OR DISTRIBUTION killed (there is no mention of Noah needing to collect seeds interpretation of Genesis was correct, God had created plants to save the plants), and Earth had to be completely repop- and animals with the wrong properties to fit into a system ulated with all types of animals and birds starting with just that would be perfectly balanced and unchanging to the end one male© Jones and one & female Bartlett of each Learning, of the unclean LLC animals and of time. They© realizedJones that & theBartlett story of Learning,Genesis as well LLCas their just six males and six females of each of the clean animals own research pointed not to a stable, harmonious, gardenlike (GenesisNOT states FOR that SALE Noah sacrificed OR DISTRIBUTION one male and one Earth but ratherNOT to oneFOR of changeSALE and OR competition, DISTRIBUTION of some female of each type of clean animal after the doors of the organisms increasing at the expense of others. Population Ark were opened). biology was born and has thrived ever since.

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few other genera; these are the “fern allies” you will see in wildflower books (see Figure 2-30). The second clade © Jones was& Bartlett a bit slower Learning, at the start, LLC and for millions of years was© Jones & Bartlett Learning, LLC NOT FORovershadowed SALE OR byDISTRIBUTION the abundant members of the lycophyteNOT FOR SALE OR DISTRIBUTION clade. Many of the early members became extinct, but this clade produced all the ferns and seed plants. The term most often used now is the euphyllophyte clade (pronounced YOU fill oh fight). The ferns make up a subclade of the euphyllophytes, ©and Jones they have & Bartlettbeen very successfulLearning, LLC © Jones & Bartlett Learning, LLC without having seeds (seeNOT Figures 2-31 FOR SALE and 2-32).OR DISTRIBUTION Ferns NOT FOR SALE OR DISTRIBUTION thrive in all sorts of habitats, not only shady, damp forests, but also hot, dry deserts. They never produce wood, so they are all herbs, even the very tall ferns called tree ferns. Some ferns have evolved to have sophisticated relation- A ships ©with Jones ants, relationships & Bartlett that Learning, are mutually LLC beneficial. © Jones & Bartlett Learning, LLC (See FigureNOT 14-19D.)FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The ferns make up a well-defined subclade within the euphyllophyte clade, but we are not certain how to group the remaining vascular plants. Many are known only as fossils of isolated leaves or wood or reproductive organs; it is very © Jones &rare Bartlett to ever find Learning, a fossil of anLLC entire plant with all parts still© Jones & Bartlett Learning, LLC NOT FORattached SALE to OR each DISTRIBUTION other. Some especially intriguing fossils NOT FOR SALE OR DISTRIBUTION look like fern leaves with seeds on them, so they were named “seed ferns.” But no seed fern is alive today, and no living fern ever has anything that even slightly resembles a seed. We believe that the name “seed fern” was a poor choice, but by now it is very commonly© Jones used. The & Bartlettmany fossils Learning, of seed LLC © Jones & Bartlett Learning, LLC ferns are too incompleteNOT for us FOR to know SALE if there OR was DISTRIBUTIONonly one B NOT FOR SALE OR DISTRIBUTION group of early seed plants or several. If there was only one group of seed ferns, then probably seeds evolved just once. If so, all seed plants make up one clade, the seed plants (more technically, spermatophytes). But if seeds evolved two or© three Jones times, & then Bartlett “seed plants” Learning, is not a clade,LLC not a © Jones & Bartlett Learning, LLC closelyNOT related FOR group SALE that all ORdescended DISTRIBUTION from the same com- NOT FOR SALE OR DISTRIBUTION mon ancestor. If seeds evolved several times, “seed plants” would then be the name of a grade and could only be used informally. Other extinct seed plants lived after seed ferns. Many © Jones &look Bartlett like intermediates Learning, in the LLC evolution of modern seed plants© Jones & Bartlett Learning, LLC NOT FORfrom SALE seed ferns,OR DISTRIBUTIONbut the picture is not yet clear. Many peopleNOT FOR SALE OR DISTRIBUTION are taking a cautious approach now, tentatively considering all the seed plants as being related. They assume that seed plants C evolved only once, and then diverged into several major FIGURE 2-34 (A) These avalanche lilies (Erythronium montanum) groups, most of which have some members that are still alive are shown as representative monocots, but the monocots are a today. According to this© theory Jones (which & isBartlett the one followed Learning, large,LLC diverse group. Many have large© Jones showy flowers, & Bartlett although Learning, LLC in this book), the early seedNOT plants FOR gave SALE rise to these OR clades:DISTRIBUTION flowers of grasses and sedges areNOT small. FORMost monocotsSALE OR DISTRIBUTION cycads, gnetophytes, Ginkgo, conifers, and angiosperms. have parallel venation in their leaves, and many die back to Until recently, it was thought that all members of a persistent subterranean bulb or rhizome. (B) These Joshua the angiosperm clade were either monocots or dicots trees (Yucca brevifolia) are shown as another representative (FIGURE 2-34). We used to think that after the first flower- type of monocot. Many people think of monocots as small, ing plants© Jones originated, & Bartlettthe group immediately Learning, diverged LLC into delicate plants© like Jones lilies, irises, & Bartlett crocuses, and Learning, so on, but many, LLC such as Joshua trees, become very large and tough; other two distinct clades, monocots and dicots. But new evidence NOT FOR SALE OR DISTRIBUTION strong monocotsNOT are FOR palms, SALEagaves, yuccas, OR DISTRIBUTION bamboos, and indicates that split did not occur immediately. Early flower- many bromeliads. (C) This lupine, Lupinus latifolius, is shown as a ing plants evolved and diverged into several groups before representative eudicot, but eudicots are a gigantic and diverse the monocots originated and became so distinctive. The term group. Of the plants you see every day, unless a plant is obviously “dicot” had referred to all the angiosperms except monocots, a monocot, conifer, or fern, then it is probably a eudicot. Eudicots © Jones &but Bartlett like the term Learning, “gymnosperm,” LLC this is unacceptable because it© Jonescan be trees,& Bartlett shrubs, herbs, Learning, vines, parasites, LLC and succulents, as NOT FORdoes SALE not include OR DISTRIBUTIONall the descendants of the common ancestor ofNOT well FOR as many SALE other ORtypes DISTRIBUTION of plants. 44 Chapter 2: Overview of Plant Life

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the group (it leaves out monocots). At present, we use the terms and have only recently arrived in the southern United States. basal angiosperms for those angiosperms that diverged early; Unfortunately, sabre-tooth tigers migrated south, and as © Jones monocots& Bartlett for theLearning, clade of lilies, LLC palms, agaves, orchids, and © Jonesthey spread & Bartlett into South Learning, America they LLC killed off many large NOT FORtheir SALE relatives; OR and DISTRIBUTION eudicots (pronounced you DIE cots) for allNOT animal FORs, drivingSALE many OR speciesDISTRIBUTION to extinction. Cacti originated the rest of the angiosperms. You will still see the term “dicot” in South America and were confined to just that continent used in many books, and it most often means “basal angio- until continental drift finally brought North and South sperms plus eudicots.” America together; cacti could migrate north into Mexico and Although the terms “dicot,” “gymnosperm,” and “fern the deserts of the United States as animals carried their seeds allies” are being abandoned,© Jones it is good & for Bartlett you to know Learning, why LLC(FIGURE 2-35). The creosote ©bush Jones that gives & allBartlett the deserts Learning, LLC they were invented and NOThow they FOR were SALE being used. OR Even DISTRIBUTION of the southwestern United StatesNOT their FOR distinctive SALE aroma OR also DISTRIBUTION though you will still see them occasionally, it is best if you came from South America (FIGURE 2-36). avoid using them.

❚❚ Overvie© Jones &w Bartlett of Plant Learning, Ecology LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Plants live in a complex, dynamic, and changing world. Earth’s complexity is easy to see. Some areas are mountainous with cold temperatures and thin, rocky soil, but other areas are low, warm, and moist. Volcanoes release lava and ash that are © Jones &initially Bartlett sterile Learning,but that gradually LLC change into rich acidic soil.© Jones & Bartlett Learning, LLC NOT FORIn SALE contrast, OR limestone DISTRIBUTION breaks down to form alkaline soil. In NOT FOR SALE OR DISTRIBUTION addition, some soils are so rich in certain minerals they are toxic and plants cannot grow on them, whereas other soils have a balance of mineral nutrients that encourages luxuriant plant growth. On mountains and in valleys, the slopes that face the equator receive ©more Jones sunlight & and Bartlett are much Learning, warmer LLC © Jones & Bartlett Learning, LLC than the sides that face away.NOT FOR SALE OR DISTRIBUTIONFIGURE 2-35 This cactus, StetsoniaNOT coryne, FOR is at SALE home in OR DISTRIBUTION Earth is dynamic—energetic—for many reasons. As Earth Argentina; it is one of many South American cacti. For almost any rotates on its axis, a particular area faces the hot sun during cactus you would encounter north of the Panama Canal, similar the day but faces the extreme cold of outer space at night. but unrelated species exist in South America. Cacti were not Throughout a year, seasons change from spring to summer and present in North America until continental drift brought North so on,© each Jones characterized & Bartlett by the amountLearning, of energy LLC available and South America© Jones close enough & Bartlett together Learning, for seeds to be LLC carried northward. from NOTsunlight. FOR Earth’s SALE atmosphere OR andDISTRIBUTION its oceans are two NOT FOR SALE OR DISTRIBUTION gigantic fluids that circulate, moving energy from place to place. We experience the circulation as cold fronts of frigid polar air that move southward, pushing warm air aside, or as storms and hurricanes that carry water and energy in such © Jones &concentrated Bartlett forms Learning, they destroy LLC buildings and push over trees.© Jones & Bartlett Learning, LLC NOT FOR SALEEarth’s OR hot interiorDISTRIBUTION is another source of energy that affectsNOT FOR SALE OR DISTRIBUTION life on the planet’s surface. Erupting volcanoes catch our attention, but Earth’s interior heat also powers continental drift (technically known as plate tectonics): Hot, molten rock rises along the center line of each ocean then spreads outward as newly formed sea floor.© JonesThis pushes & Bartlettthe old sea Learning, floor to the LLC © Jones & Bartlett Learning, LLC side, which, in turn, pushesNOT continents FOR SALE from place OR to DISTRIBUTIONplace. NOT FOR SALE OR DISTRIBUTION North and South America formerly were widely separated by thousands of miles, but the continental drift of each changed direction and now they are moving toward each other. Central America is the result of this collision, which is still occur- ring: North and South America first made contact with each FIGURE 2-36 Creosote bush (Larrea tridentata) is at home in the © Jones & Bartlett Learning, LLC deserts of North© JonesAmerica but& itsBartlett closest relative, Learning, Larrea divaricata LLC other less than 2 million years ago. As they continue to push NOT FOR SALE OR DISTRIBUTION and two otherNOT species FOR of Larrea SALE, live in OR South DISTRIBUTION America. The plants into each other, they crumple Earth’s crust, pushing Central in South America resemble those in North America so closely America upward and causing numerous volcanic eruptions that we believe that at some very recent time a seed or two of throughout the region. As the two continents finally came L. divaricata was carried northward the entire distance and then into direct contact, many animals and plants could migrate thrived in the new habitat. Once in North America, the plants © Jones &from Bartlett one to the Learning, other. For example, LLC armadillos have been © Jonesgradually & evolvedBartlett just enoughLearning, that we LLC consider them to be a new NOT FORslowly SALE migrating OR DISTRIBUTION from South America into North America, NOTspecies, FOR L. SALE tridentata OR, distinct DISTRIBUTION from the ancestral L. divaricata. Overview of Plant Ecology 45

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Earth is a changing world. For comparison, think about our moon: It is complex but not dynamic. The craters we © Jones see& Bartletttoday are the Learning, same as they LLC were thousands or millions © Jones & Bartlett Learning, LLC NOT FORof SALE years ago, OR with DISTRIBUTION the only new activity to ever occur is an NOT FOR SALE OR DISTRIBUTION occasional new meteor strike. But Earth is never the same, not even from one year to the next. Mountains are lifted by volcanism or continental collision, and they are worn down by erosion. Flooding rivers carry silt that settles into rich deltas and marshlands filled© Jones with life. & FiresBartlett drastically Learning, alter LLC © Jones & Bartlett Learning, LLC the numbers of plants andNOT animals FOR in forestsSALE and OR prairies DISTRIBUTION that NOT FOR SALE OR DISTRIBUTION burn. As continents drift, their changing positions affect the circulation of the oceans, and thus the circulation of heat and moisture. During the time North and South America were widely separated, the Pacific and Atlantic Oceans were in contact© andJones water &circulated Bartlett around Learning, each continent. LLC But once FIGURE 2-37© ForJones most of & us, Bartlett it is difficult Learning, to imagine LLCwhat the continentsNOT FOR collided SALE and formed OR DISTRIBUTION Central America, oceanic Earth was likeNOT before FORthe evolution SALE of trueOR plants: DISTRIBUTION No life was circulation was altered. Water was forced to flow northward present on land at all. For billions of years, life existed as bacteria and southward, carrying warm water toward the poles and and archaeans in the oceans; later there were fish and algae, but making those areas warmer than they had been before. Plants nothing at all on land until, at the earliest, about 450 million years and animals located in the far northern parts of North Amer- ago. Most of the surface was rock, and if any soil particles formed, © Jones &ica Bartlettand Europe Learning, experienced climaticLLC warming. © Jonesthey would & Bartlett have mostly Learning, been washed LLCinto the oceans because Much earlier than that, just before plants evolved from there were no plant roots to hold them in place. The area shown NOT FOR SALE OR DISTRIBUTION NOThere FOR is in DeathSALE Valley OR National DISTRIBUTION Park, which does have plant and green algae, all continents had drifted together into one gigan- animal life, but it is widely scattered and confined to areas with at Pangaea tic continent called (pronounced pan GEE uh). This least occasional water. was so enormous that its center was a desert: Storms blowing in from the oceans would rain themselves out before they could reach the center of© the Jones supercontinent. & Bartlett But because Learning, all LLCsuch that it is a better habitat for© organisms Jones that& Bartlett respire, and Learning, LLC land was connected, theNOT newly FORevolved SALE plants could OR spreadDISTRIBUTION vice versa, organisms that respireNOT are a FOR source SALEof the carbon OR DISTRIBUTION easily from place to place such that by the time Pangaea dioxide needed by photosynthetic organisms (FIGURE 2-38). broke apart, each new continent carried some plants, and no Plants, animals, and all other organisms interact in more continent was left without any plants. The first splitting of immediate, direct ways as well. Interactions may involve one Pangaea ran from east to west, creating two gigantic conti- organism benefiting by harming the other (this is predation), nents,© Laurasia Jones (North & Bartlett America, Learning, Europe, Russia, LLC and China by both organisms© Jones helping & each Bartlett other (mutualism), Learning, by LLCone in theNOT north) FOR and Gondwana SALE OR (Africa, DISTRIBUTION South America, India, organism benefittingNOT FOR without SALE harming OR the DISTRIBUTION other (commensal- Australia, and Antarctica in the south). Imagine if Pangaea ism), or by one organism harming another with no benefit to had broken apart before plants evolved from algae. Plants itself (amensalism) (TABLE 2-6). Herbivores and omnivores would have originated on one continent but not the other. On are examples of predation. They benefit by eating plants; this one continent, plants would have spread and diversified, and of course harms the plants, so plants need to defend them- © Jones &would Bartlett have evolved Learning, into many LLC clades. But the other continent© Jonesselves from & Bartlett animals. There Learning, is no one LLC single optimal defense; NOT FORwould SALE have OR remained DISTRIBUTION barren until, at some point millions ofNOT instead FOR many SALE alternative OR DISTRIBUTION types of defense have evolved, such years later, some spores or seeds would have somehow blown as having spines or being poisonous (FIGURE 2-39). Patho- or drifted to it (FIGURE 2-37). genic fungi and bacteria also prey on plants. A crucial cause of Earth being a changing world is life Animals often harm plants without benefiting from the itself. Living organisms take up energy and nutrients from damage they do; this is an amensal relationship. For example soil, water, and air and then© Jones release their & Bartlett waste products Learning, back. theyLLC trample plants as they walk© across Jones them & or Bartlett when they Learning,lie LLC Plants take so much carbonNOT dioxide FOR out SALE of the air OR that DISTRIBUTION they down. Here, too, it is beneficialNOT for plants FOR to somehowSALE ORdefend DISTRIBUTION have changed the atmosphere. And because carbon dioxide is themselves. a greenhouse gas, the changing levels of carbon dioxide affect The presence of trees often creates a shady, cool area in the temperature of Earth’s surface—the biosphere—the place which smaller plants, such as mosses and ferns, can live. The where life occurs. Photosynthesis produces oxygen as a waste shade-loving plants benefit without affecting the trees; this is a product© Jonesthat is released & Bartlett into the air.Learning, Before the evolutionLLC of commensal relationship© Jones (&FIGURE Bartlett 2-40 ).Learning, LLC photosynthesis,NOT FOR Earth SALE had no OR free DISTRIBUTIONoxygen at all; there was no In mutualisticNOT relationships, FOR SALE both OR organisms DISTRIBUTION benefit. When aerobic respiration nor were there any animals. The photosyn- animals pollinate flowers, both the plant and the animal thetic production of oxygen is carried out by cyanobacteria, benefit: The animal obtains nectar or pollen as food, and algae, and plants; without these organisms, animals and fungi plants have their pollen grains carried from one flower to could not exist. Similarly, as animals and fungi respire their others, improving cross-pollination and sexual reproduction. © Jones &food, Bartlett they give Learning, off carbon dioxide, LLC which of course is valuable© JonesThe evolution & Bartlett of fleshy, Learning, nutritious fruitsLLC is similar: Animals NOT FORfor SALE plants. ThusOR DISTRIBUTIONphotosynthetic organisms have changed EarthNOT benefit FOR bySALE eating theOR fruits DISTRIBUTION whereas plants benefit from having 46 Chapter 2: Overview of Plant Life

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A © Jones & Bartlett Learning, LLC B © Jones & Bartlett Learning, LLC FIGURENOT 2-38 FOR (A) The SALE grass and OR herbs DISTRIBUTION here capture energy and minerals, convertingNOT them FOR into the SALE organic ORmolecules DISTRIBUTION of the plants’ bodies. Herbivores such as deer eat the plants, using the organic compounds as their own food. The respiration of the animals returns carbon dioxide back to the air; the animal dung also is broken down by fungi, releasing carbon dioxide. Thus, there is a cycling of carbon dioxide, minerals, oxygen, and other components. (B) In addition to large mammals such as deer, insects such as this caterpillar also consume immense amounts of plant material and are an important component of the carbon, nitrogen, and mineral cycles. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TABLE 2-6 Direct Interactions Among Organisms

Neutralism Neither organism benefits or is harmed.

Mutualism Both organisms benefit. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Predation One organism benefits by harming another. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Commensalism One organism benefits, whereas the other is neither harmed nor helped.

Amensalism One organism harms another without © Jones &receiving Bartlett any benefitLearning, itself. LLC © Jones & Bartlett Learning, LLC CompetitionNOT FOR BothSALE organisms OR DISTRIBUTIONharm each other. NOT FOR SALE OR DISTRIBUTION

FIGURE 2-40 Two trees have died and fallen across this stream, which keeps their wood moist enough for moss plants to grow on them. The mosses are benefitting from the presence of these © Jones & Bartlett Learning, LLC © Jonesdead trees, & Bartlett but the trees Learning, are deriving no LLC benefit at all from the NOT FOR SALE OR DISTRIBUTION NOTmosses. FOR Similarly, SALE surrounding OR DISTRIBUTION trees that are still alive provide shade that is beneficial to the mosses, but the mosses provide no benefit to the living trees either.

© Jones & Bartlett Learning, theirLLC seeds disbursed, often in ©a pileJones of “organic & Bartlett fertilizer” Learning, LLC NOT FOR SALE OR DISTRIBUTION(FIGURE 2-41). These cases ofNOT mutualism FOR differ SALE fundamen OR- DISTRIBUTION tally from those of predation and amensalism. In predation, for example, the organisms are battling against each other. When an animal eats a plant, some surviving seedling of that plant might have a defensive mutation that might make © Jones & Bartlett Learning, LLC it more spiny© or Jones poisonous & thanBartlett its parent Learning, was. If so, that LLC FIGURE 2-39 This pasture is being overgrown by prickly poppy seedling is more likely to survive and, over many generations, (ArgemoneNOT albiflora FOR) becauseSALE cattleOR andDISTRIBUTION deer will not eat it even if NOT FOR SALE OR DISTRIBUTION starving. The leaves and stems are covered with spines; it contains spininess or toxicity may gradually increase in that species of a toxic milky juice as well. If there were no herbivores, the grasses plant. But if so, then it will be helpful to the animals if they might grow well enough to compete against the prickly poppy have mutations that allow them to overcome the plant’s new and drive it out, but with cattle eating the grass, the prickly defenses. This battle between plants and animals has con- © Jones &poppies Bartlett have a Learning,distinct advantage LLC and might eventually take © Jonestinued for& Bartlettthe hundreds Learning, of millions ofLLC years that both have NOT FORover SALE the entire OR pasture. DISTRIBUTION NOTexisted. FOR SALE OR DISTRIBUTION Overview of Plant Ecology 47

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FIGURE© Jones 2-41 This & pile Bartlett of Texas lignum-vitae Learning, (Guaiacum LLC © alxpin/iStockPhoto© Jones & Bartlett Learning, LLC angustifoliumNOT FOR) seeds SALEhas passed OR through DISTRIBUTION an animal, probably FIGURE 2-42NOT Orchids FOR have SALE extremely OR complex DISTRIBUTION flowers as the a javalina, so all the fruit pulp has been digested but the seeds result of coevolution between each species of orchid and one are intact. Five have already germinated. The javalina probably particular species of pollinator. The benefit of this to the plant is ate the fruits far from this area and then defecated here, thus that a pollinator carries the orchid’s pollen only to other flowers spreading the seeds away from the parent plant. Both the plant of the same species; none is wasted by being accidentally carried © Jones &and Bartlett the animal Learning,benefit in this LLCmutualistic relationship. © Jonesto a different & Bartlett species ofLearning, plant. However, LLC if the pollinators die due NOT FOR SALE OR DISTRIBUTION NOTto FOR a disease SALE or bad ORweather, DISTRIBUTION the orchid then has no alternative But a completely new type of evolution began to occur means of transferring its pollen. This Phalaenopsis is popular in as animal-pollinated flowers evolved. Because plants benefit cultivation. when an animal carries its pollen to another flower of the same species, any mutation in the plant that helps the pollinator will before, there are many ways of being adapted, so there might be beneficial to both. Similarly© Jones any &mutation Bartlett in the Learning,animal that LLCbe small wildflowers growing ©between Jones the &oaks, Bartlett wildflowers Learning, LLC makes it a better pollinatorNOT helps FOR both itselfSALE and ORthe plant. DISTRIBUTION This that can tolerate growing in shadeNOT and FOR whose SALE small root OR DISTRIBUTION is called coevolution and it causes certain plants and animals systems will fit into any spaces between the roots of the oaks. to become well adapted to each other (FIGURE 2-42). Keep in Habitats are complex, so there may be rocky cliffs that are mind that at the same time that the plant’s flowers are produc- too dry for the oak trees but are just fine for junipers. In ing nectar that benefits a pollinator, the plant’s leaves may be this forest, the oak trees compete with each other for water, producing© Jones poisons & that Bartlett keep herbivores Learning, away. LLC minerals, and© light; Jones they &make Bartlett the habitat Learning, shady enough LLC for PlantsNOT interact FOR SALEwith each OR other. DISTRIBUTION Of course, plants never wildflowers,NOT and the FOR junipers SALE are usingOR aDISTRIBUTION resource (rocky eat each other; instead plants compete with each other for cliffs) that oaks cannot. water and minerals in the soil, for sunlight, and for the Because all organisms evolve, a set of organisms such as attention of pollinators and seed dispersors. In an oak forest, a forest never stays the same. At the same time, the physical for example, trees may grow so close together that the roots environment also is changing, due both to geological pro- © Jones &of anyBartlett one tree Learning, touch those ofLLC the surrounding trees and © Jonescesses and& Bartlett the effects Learning,of organisms. LLCThe biosphere is complex, NOT FORthere SALE is no OR room DISTRIBUTION for a new oak seedling. Because all the NOTdynamic, FOR SALE and changing. OR DISTRIBUTION The plants, animals, geology, and trees are the same species of oak, they probably are almost climate that were present in the past were different than they identical genetically and each is about as good as any other are now, and those of the future will also be different. But for at absorbing water and nutrients. Oaks are wind pollinated studying and understanding life, the process, principles, and so they are not competing for pollinators. But as mentioned concepts are always the same. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION At the Next Level

1. Alternatives© Jones and& Bartlett consequences Learning,. A theme of LLC this text is interesting© Jones examples & of Bartletthighly modified Learning, plants and LLC is to ask “What are the alternatives?” and “What are the well illustrated. Even as a beginning botanist, you will consequencesNOT FOR ofSALE various OR alternatives?” DISTRIBUTION Parasitic plants understandNOT most FOR of it SALEand benefit OR from DISTRIBUTION knowing how are discussed at several points because they often extreme certain alternatives can be. You might find it represent extremely unusual alternatives to the biology difficult to believe that some of these are actually plants. of nonparasitic plants. I recommend the book Parasitic 2. Evolution by natural selection. Charles Darwin and © Jones & BartlettFlowering Learning, Plants by Henning LLC S. Heide-Jørgensen (2008,© JonesAlfred & Bartlett Russel Wallace Learning, discovered LLC evolution by natural Brill Academic Publishers) because it provides many selection in the 1850s, and both evolution and natural NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 48 Chapter 2: Overview of Plant Life

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selection are dominant themes in this textbook. Darwin perfectly efficient? Are the feces and urine valuable to © Jones & Bartlettwrote The Learning, Origin of Species LLC in 1859, and it was the crucial© Jonesplants? & Bartlett Do they fertilizeLearning, plants? LLC NOT FOR SALEintroduction OR DISTRIBUTION of basic principles to the world. However INOT FOR SALEThink abo ORut an DISTRIBUTION entire grassland, covering much recommend at this point that you read Darwin’s Voyage of Yellowstone National Park, for example. Bison graze of the Beagle (1989, Penguin Books), which is his account almost all the grassland, and they urinate and defecate of his trip and his collecting. It is written as a narrative there, too, so minerals and nutrients stay within the and is wonderfully easy to read. Darwin wrote it shortly grassland. Bison eat all day long, feeding on thousands of after he returned from© Jones his voyage, & Bartlettmany years Learning, before he LLCplants, but then defecate and© urinateJones only & occasionally,Bartlett Learning, LLC had figured out theNOT principles FOR of SALEevolution OR by naturalDISTRIBUTION in one or two spots. Are theNOT plants FOR that benefit SALE from OR the DISTRIBUTION selection. As you read Voyage of the Beagle, you will have herbivores the same ones that suffer? a better understanding of evolution than Darwin did This herbivore–grass example is a form of preda- when he was writing it. In certain parts of the book, it tion, but the plants receive at least some benefit from is fascinating to see how Darwin puts the clues together the mineral-rich fertilizer. But this is not a mutualism, correctly© Jones and &comes Bartlett to key understandingsLearning, LLC using the such as a© flower Jones providing & Bartlett nectar to Learning, a pollinator. InLLC a scientificNOT FOR method. SALE But in OR other DISTRIBUTION parts, it is excruciating to true mutualism,NOT FOR the plant SALE that provides OR DISTRIBUTION nectar (the cost) read as he misses the clues and misses the point. Voyage to a pollinator is the same plant that obtains the benefit of the Beagle is an excellent example of how the scientific (pollination). method is used, how Darwin’s thought processes and 4. Grasslands. Let us think further about the grasslands in reasoning finally allowed him to see the principle that is the previous question. Imagine that all herbivores are © Jones & Bartlettthe basis ofLearning, all aspects of LLC biology. © Joneseliminated. & Bartlett If the Learning, leaves and stems LLC are not being eaten, NOT FOR 3.SALE Herbivores OR. DISTRIBUTIONLet us think more closely about interactionsNOT FORwhat SALE will happen OR to DISTRIBUTION them after they die in the autumn? between herbivores and the grasses of their habitats. How does the fate of the dead leaves and stems differ Herbivores eat grasses, a type of predation (Table 2-6). if they are in a habitat that is moist and warm as com- The plants suffer, but is it really true that they receive no pared to one that is dry and cold (moist can include rain, benefit from herbivores? What happens to the material snow, sleet; warm means that it rarely or never freezes)? eaten by herbivores?© Some Jones becomes & Bartlett part of the Learning, herbi- LLCWith no herbivores, how will© Jonesthe growth & ofBartlett the plants Learning, LLC vores’ bodies, but isNOT the digestive FOR tractSALE of an OR herbivore DISTRIBUTION be affected in the first severalNOT years FOR after SALE the removal OR DISTRIBUTION of 100% efficient? Are all the minerals and other nutrients herbivores? What other mechanisms release minerals absorbed out of their food? Is any biological process from dead plant parts if there are no herbivores?

1. Almost all plants consist of stems, leaves, and roots. 8. A grade is a level of evolution, and it is an artificial © Jones & BartlettFlowers and Learning, cones are modified LLC stems and leaves. © Jonesgroup & Bartlett because various Learning, unrelated LLC organisms might 2. One of the defining characters of angiosperms (flowering evolve to a particular level independently. A clade is a NOT FOR SALEplants) OR is that DISTRIBUTION their seeds always develop inside a fruit. NOT FORnatural SALE group OR because DISTRIBUTION it contains a common ancestor 3. The internal organization of plants is very uniform and and all the descendants of that ancestor. simple; virtually all stems have epidermis, cortex, vascular 9. There are multiple ways for an organism to be adapted tissues (xylem and phloem), and pith; roots lack pith; leaves to its environment; there is no single optimal solution to consist of epidermis,© mesophyll, Jones and& Bartlettvascular tissues. Learning, LLCany biological problem. © Jones & Bartlett Learning, LLC 4. All plants have a primary body but only woody plants 10. The biosphere is constantly changing due to physical and have a secondary body,NOT which FOR consists SALE of woodOR DISTRIBUTIONand geological forces, as well asNOT to the presenceFOR SALE of life itself.OR DISTRIBUTION bark. 11. Organisms interact with each other, often with animals 5. All organisms must take in energy and raw materials and fungi consuming plants and plants needing to defend from their environment; they also give off waste prod- themselves. But some interactions, such as pollination, ucts© Jones to the environment. & Bartlett Learning, LLC are mutually© Jones beneficial & Bartlettto both plants Learning, and animals. LLC Plants 6. AllNOT known FOR organisms SALE store OR heritable DISTRIBUTION information in DNA. also competeNOT with FOR each SALE other for OR various DISTRIBUTION resources. 7. Plants detect and respond to information from the environment as well as from various organs within the plant itself.

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IMPORTANT TERMS © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC angiosperm Gondwana NOT FOR SALE OR DISTRIBUTIONreproductive organ NOT FORbasal SALE angiosperm OR DISTRIBUTION grade respiration biosphere gymnosperm seed plant clade herb spermatophyte common ancestor Laurasia spore-bearing plant cormophyte © Jones & Bartlettlycophyte Learning, clade LLC thallophyte© Jones & Bartlett Learning, LLC cryptogam NOT FOR SALEmonocot OR DISTRIBUTION thallus NOT FOR SALE OR DISTRIBUTION dicot nonvascular plant tracheophyte embryophyte Pangaea vascular plant eudicot phloem vegetative organ euphyllophyte clade photosynthesis woody plant fern © Jones & Bartlett Learning,plant LLC © Jonesxylem & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION REVIEW QUESTIONS

1. Name the three vegetative organs of a plant. 11. Evolution by natural selection causes organisms to © Jones &2. Bartlett How do th Learning,e reproductive LLC organs of ferns differ from © Jonesbecome & Bartlett more adapted Learning, to their environment.LLC Is the envi- NOT FOR SALEfoliage OR leaves? DISTRIBUTION NOT FORronment SALE uniform OR acrossDISTRIBUTION all of Earth? Does the environ- 3. Name the four basic organs of a flower. Describe situ- ment change with time? Considering this, do you think ations in which flowers might not need one or two of that there is only one single optimum way for a plant to these organs. be adapted? If not, what is the alternative? 4. Name the two vascular tissues found in vascular plants. 12. Have North and South America always been connected What does each transport?© Jones & Bartlett Learning, LLCby Central America? Once© the Jones two continents & Bartlett joined, Learning, LLC 5. Are there any typesNOT of organisms FOR SALEthat do notOR need DISTRIBUTION plants and animals could moveNOT from FOR one SALE to the other; OR DISTRIBUTION to take in energy and raw materials from their envi- animals can walk, fly, or swim, but how does a plant ronment? Discuss the source of energy for plants as species spread from one area to another? South America opposed to animals; describe some of the raw materials has thousands of plants adapted to the Amazon rainfor- that are needed by plants. est; do you think it is likely that any of those plants will © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 6. is the central metabolism be able to migrate to North America across the deserts byNOT which FOR plants SALE acquire ORenergy; DISTRIBUTION it occurs only when of Mexico,NOT Texas, FOR and SALEArizona? OR DISTRIBUTION , , 13. The concept of biosphere was touched on only briefly and are present. in this chapter, but you have many resources in this text 7. Each plant receives a great deal of information from and online to explore this concept. What are some of its parents by means of the DNA in which two cells? the geological and biological components of the bio- © Jones & BartlettDescribe theLearning, types of information LLC that plants receive © Jonessphere? & Bartlett We humans Learning, are burning LLC fossil fuels and adding NOT FOR SALEfrom theOR environment. DISTRIBUTION Why is it that environmental NOT FORcarbon SALE dioxide OR to theDISTRIBUTION atmosphere; how does this affect information cannot be stored in DNA? the biosphere? 8. The activity of the roots of a plant must be coordinated 14. Plants and animals usually battle each other; describe with the activity of leaves. Describe how this occurs. why and how this occurs. Once animal-pollinated flow- What type of information molecule is used? ers evolved, a new type of plant–animal interaction was 9. Which three groups© of Jones plants are & referred Bartlett to as Learning, bryo- LLCpossible; describe it. How is© it Jonespossible for & aBartlett mutation in Learning, a LLC phytes? They differNOT from FOR all other SALE plants ORin two DISTRIBUTION main plant to be beneficial for bothNOT the FORplant and SALE for an ORanimal? DISTRIBUTION features; name the features. 15. Earth is constantly changing, and so are all organisms 10. Which group of plants does the term “angiosperm” as they evolve. But despite so much change, it is possible refer to? What are the three main subgroups of angio- to study and understand life because several things are sperms? Do angiosperms have vascular tissue? Do they always constant; what are those things? have© Jones seeds? In & conifers, Bartlett seeds Learning, develop inside LLC cones, © Jones & Bartlett Learning, LLC butNOT in angiosperms, FOR SALE seeds OR always DISTRIBUTION develop inside of NOT FOR SALE OR DISTRIBUTION .

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Design Credits: Did You Know: © Daniel Bruce/FlatIcon; Alternatives: © Dhoxax/Shutterstock; Plants and People: © alxpin/iStockPhoto; Botany and Beyond: © Kenny Yeoh/Shutterstock; At the Next Level: © Freepik/FlatIcon; all photos, unless otherwise credited, NOT FORare courtesySALE of James D.OR Mauseth DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 50 Chapter 2: Overview of Plant Life

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