BIOL3316 Plant Diversity Week 10 Angiopsperms

BIOL3316 Chapter 19 Angiosperms

Domain Eukarya Kingdom Plantae

Phylogenetic tree of plants.

Angiosperm Classification 4. Flowering Plants Phylum Anthophyta (angiosperms, or flowering plants) Synapomorphies that link the angiosperms Largest phylum of photosynthetic organisms. All have: (These characters were present in the common ancestor § Flowers that provide a means of exchanging genetic of all angiosperms): information. Both male and female reproductive structures are § Flowers much smaller than the gametophytes of non-flowering plants: § Fruit • Stamens are the reproductive structures found in flowers that § Rolled and closed megasporophylls (carpels) produce pollen grains that carry the male genetic information. These are small more easily spread from flower to flower. § Double fertilization (and the resulting triploid • Smaller female reproductive parts allow them to produce seeds endosperm) more quickly. § Three-nucleate microgametophyte (pollen) • Allows the process of fertilization and seed formation to occur § rapidly. Eight-nucleate megagametophyte § Carpels enclose developing seeds and may turn into a fruit. § Absence of archegonia in megagametophyte § Production of endosperm (a material that forms after § Anthers with two pairs of pollen chambers fertilization and serves as an initial food source for the § Sieve tubes and companion cells in the phloem developing seed and seedling).

Characteristics of monocots: Most angiosperms belong to one of two classes: the Monocotyledones (“monocots”) or the Eudicotyledones (eudicots, AKA, “dicots”).

Scattered vascular bundles. A) vascular bundle; B) ground tissue. Parallel leaf venation.

Flower parts in multiples of 3.

Page 1 BIOL3316 Plant Diversity Week 10 Angiopsperms Characteristics of dicots: Flower Structure Flowers are the reproductive structure of angiosperms. A flower is a shoot bearing sporophylls. All flowers have at least one carpel and/or one stamen. § Carpel: a structure in a flower that contains the female reproductive parts. Consists of a style, a stigma and an ovary. The carpel or carpels in a flower make up the gynoecium. • Style: the (usually elongated) part of a carpel through which pollen tubes grow. Flower parts in multiples of 4 or 5. • Stigma- At the top of the style, it is the location on the carpel that receives the pollen. The stigma and style together are often called the pistil. • Ovary: the part of a carpel that encloses the ovules. § Stamen: a microsporophyll a structure in a flower that contains the male reproductive parts: • Consists of a slender stalk, or filament, upon which is a two-lobed Vascular bundles in a ring. A) epidermis; anther containing four microsporangia, or pollen sacs, in two pairs. B) vascular bundle; C) ground tissue; D) • Stamens make up the androecium. Net-like leaf venation. cortex.

Flower! Flower! Structure Structure

Fig. 19-6. Lily flower.

Flower Structure Flower Structure

Flowers are categorized by describing the presence/absence of flower parts: § A complete flower contains a perianth (calyx and corolla), an androecium, and a gynoecium: • The calyx has all of the sepals in the flower. • The corolla has all of the petals in the flower. § A bisexual (“perfect”) flower contains both an androecium and gynoecium. § A unisexual (“imperfect”) flower contains either an androecium or gynoecium: • Staminate: the flower contains the androecium. • Carpellate: the flower contains the gynoecium. A monoecious plant contains both staminate and carpellate flowers on the same individual. In a dioecious plant, the staminate and carpellate flowers are on different individual Fig. 19-12. Apple flower. plants.

Page 2 BIOL3316 Plant Diversity Week 10 Angiopsperms Flower Structure Flower Structure Flowers may be borne singly, on a peduncle, or in a § An indeterminate inflorescence has new buds growing at the cluster called an inflorescence. The tiny stalk of an apex while mature flowers appear on lower pedicels. Buds individual flower in an inflorescence is called a pedicel. open first from the base of the inflorescence. § A determinate inflorescence has new buds growing at the base while mature flowers appear on upper pedicels. Buds open first at the top of the inflorescence.

Flower Structure Flower Structure Position of ovary in a flower: Placentation: The position of the ovary has to do with where flower parts are § Placenta–the part of the ovary where the ovules are attached (‘inserted’), in relation to the ovary. If the sepals, petals, attached and remain until! and stamen are attached below the ovary, the ovary is superior. If attached near the top of the ovary, the ovary is inferior: maturity. § Hypogynous (superior ovary)–perianth and androecium are § The arrangement of the! inserted below the gynoecium. placenta (or placentae) in! § Perigynous (also a superior ovary)–perianth and androecium are the ovary, and the! attached to the rim of a cuplike or tubular structure (hypanthium) arrangement of the ovules,! that surrounds the gynoecium. § Epigynous (inferior ovary)–the hypanthium is fused, and the differs among different! perianth and androecium! types of flowering plants. appear to be inserted at! the top of the ovary.

Fig. 19-9. Different types of! Fig. 19-11. placentation in ovaries.

Angiosperm Diversity Angiosperm Diversity There are more than 60 Orders of Angiosperms, and more The exact reasons for angiosperm success are than 300,000 known species. unclear: § Traditionally, the orders are arranged by flower § Do specialized anatomies and functions, increase structure, plus some other morphological characters. speciation rates or decrease extinction rates? § Evidence from molecular biology is rearranging the § The role of flowers in the diversification and increased taxonomy. For example, ‘monocot’ and ‘dicot’ are no phenotypic diversity may depend on the system: longer valid descriptors. • Plants such as orchids have packets of pollen and Plant reproduction by means of flowers has long high pollination precision. been thought to promote the success and • Other plants with granular pollen are less precise. diversification of angiosperms. Hedging against extinction likely represents a § The major source of angiosperm diversity is floral specialization: adapting the flower to specific tradeoff between enhancing local reproductive pollinators. Ostensibly, this limits wasted reproductive success and occupying new locations or ecological effort. niches.

Page 3 BIOL3316 Plant Diversity Week 10 Angiopsperms Angiosperm Evolution Angiosperm Evolution The ancestors of flowering plants diverged from gymnosperms during the Triassic Period (245–202 Mya). § Fossils of angiosperm-like pollen have been dated to between 247.2–242 Mya, suggesting that angiosperms § Although disputed, the early Jurassic Nanjinganthis may have evolved much dendrostya from China seems to have had several earlier than previously exclusively angiosperm features, e.g., a thickened thought. receptacle with ovules. § The early-middle Jurassic Schmeissneria, which as been considered to be a type of ginkgo, may be the earliest known angiosperm (or a close relative).

BIOL3316 Chapter 19 Angiosperm Evolution Angiosperm Evolution Between the early and late Cretaceous (about 100.5 million to 66 million years ago), angiosperms further diversified and dispersed: § Many woody angiosperms evolved during that time, as did several modern groups, such as the ancestors of magnolias, laurels, sycamores and roses. § Herbaceous plants such as water lilies! and some of the early monocotyledons! (ancestors of modern grasses) also! § A few angiosperm leaves and flowers date from the Cretaceous, evolved during that time. ca. 125-113 Mya. § Some of the oldest and most diverse! § A 2015 reanalysis of fossils of the aquatic plant Montsechia vidalii, indicate that they date from ca. 130 Mya. angiosperm groups are found in Africa! § Angiosperms diversified extensively during the early Cretaceous near the Equator, followed by low-latitude, angiosperms in (145–65 Mya). They became widespread by 120 Mya, and North America. replaced gymnosperms as the dominant trees between 100–60 § Angiosperms are thought to have evolved near the Equator Mya. They have dominated since the Cenozoic Era began. and radiated into new biomes as they spread toward the poles.

Angiosperm Evolution Angiosperm Evolution § Between ca. 100.5–93.9 Mya, angiosperms § The evolution of seed plants and later angiosperms appears to be the result of two distinct rounds of whole probably dominanted vegetation along many genome duplication. This paleopolyploidy could either: coastal tropical and, following the coasts • Double the genome of a single species (autopolyploidy) northward and southward. • Combine the genome of two species (allopolyploidy). § During this time, angiosperms also spread to § Because of functional redundancy, genes were rapidly low-elevation warm temperate and inland silenced or lost from the duplicated genomes. Most paleopolyploids have lost their polyploidy by a process continental areas. called diploidization, and are currently considered § Between ca. 95 million–93.9 Mya, therefore, diploids. angiosperms became the predominant form of § These events occurred ca. 319 Mya and ca. 192 Mya. vegetation in many areas of the world. Another possible event ca. 160 Mya perhaps created the ancestral line that led to all modern flowering plants: • This last event was studied by sequencing the genome of Amborella trichopoda (addresses Darwin’s “abominable mystery”).

Page 4 BIOL3316 Plant Diversity Week 10 Angiopsperms Angiosperm Evolution Angiosperm Diversity and Coevolution During the early Cretaceous, angiosperms Angiosperms developed a close association underwent rapid genome downsizing, while with insect pollinators early in their evolution: genome sizes of ferns and gymnosperms remained § This promoted outcrossing, resulting in unchanged. genetically vigorous offspring. § Smaller genomes (with smaller nuclei) allow for § The short generation time in which angiosperms smaller cells and faster cell division rates. reproduce relative to gymnosperms allows rapid § Species with smaller genomes can contain more smaller population growth and easier colonization of cells (particularly veins and stomata within their leaf volume. disturbed habitats. • Facilitates faster growth and higher rates of leaf gas § The seeds of angiosperms are small and can be exchange (transpiration and photosynthesis). eaten and otherwise transported to new areas by • Increased uptake of CO2 (despite concurrent decrease in animals. atmospheric [CO2]) was a competitive advantage. § Fruits further refine seed dispersal.

Flower Color and Pollinator Angiosperm Fruits About 75% of all flowering plants require the help Fruits have two major and two minor functions: of pollinators. Because most pollinators fly, the § Protection of seeds: fruits ripen as the seeds colors of a flower must attract them. The brighter mature. the flower, the more likely it will be visited. § Dispersal of seeds: Fruits assist in the § Bees are attracted to bright blue and violet colors. transportation of seeds to new areas by § Hummingbirds prefer red, pink, fuchsia or purple flowers. animals and other mechanisms. § Butterflies prefer bright colors such as yellow, § Rotting fruits may help fertilize the soil orange, pink and red. around seeds (relatively rare). § Night-blooming flowers are generally white they § Some fruits (e.g., black walnuts) have attract moths and bats using odors. allelopathic substances that prevent seedlings § Flowers may have “honey guides” that are visible in from growing too close to the parent. the UV range.

Types of Fruits Fruits and Seed Dispersal § Drupe (or stone fruit) is a fruit in which an outer fleshy part (exocarp, or skin; and mesocarp, or flesh) surrounds a single shell (the pit, stone, or pyrene) of hardened endocarp with a seed (kernel) inside, e.g., plum, peach, avocado. § Pome: composed of one or more carpels surrounded by accessory tissue, e.g., apple, pear, quince. The core is the true fruit. § Berries: are the most common type of fleshy fruit. The entire outer layer of the ovary wall ripens into a potentially edible pericarp. May be formed from one or more carpels from the same flower. • Botanical and common definitions differ: grapes, tomatoes, cucumbers, eggplant, chili peppers, and bananas are berries, while blackberries and raspberries are not. § Nuts: a fruit composed of an inedible hard shell and a seed, which is generally edible. • In general usage, a wide variety of dried seeds are called nuts, but in a botanical context ‘nut’ implies that the shell does not open to release the seed. Acorns and chestnuts are nuts, while walnuts and cashews are not.

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