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Home , Plant physiology

General the main sensitive able to absorb solar energy in both and is

this chlorophyll is contained with the probably the most characteristic “thing” that plants “do” is photosynthesis plants also have other “accessory ”:

– mainly yellow, orange almost all plants are autotrophs but usually their are masked by an abundance of !use energy from the sun to make and chlorophyll

other organic out of simple fall colors are seen as a deciduous plant shuts down and chlorophyll is broken down and recycled leaving the colors of the other pigments photosynthesis requires dioxide & come from made to protect as they recycle nutrients from the breakdown of chlorophyll CO2 enters through stomata or pores

[Application] water is absorbed through researchers are studying the structure of the chloroplasts to light improve efficiency in the design of solar collectors

CO2 + H2O sugar + O2 chlorophyll (glucose) today (2006) the most efficient solar cells capture only ~17% of solar energy that lands on them, while plant [photosynthesis converts water and carbon dioxide capture 30-40% to sugar and ]

!these can then be broken down as needed for energy photosynthesis uses several chemical pigment to absorb the energy from sunlight

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 1 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 2

Plant Nutrition heterotrophs must eat a variety of organic compounds to build cells and to break down for energy since plants produce their own organics they require in most cases; & are most relatively few simple inorganic nutrients likely to limit plant growth (hardest to get nutrients), like most living organisms plants need some form all fertilizers contain: N, P and K, in various concentrations of Carbon, , Oxygen & Nitrogen [Application] carbon, hydrogen and oxygen come from the air in the form of CO2 H2O & O2 & gardening plants, mostly nonnative species, are nitrogen & most other nutrients such as Phosphorus and selected for fast, lush growth comes from the soil: need many more nutrients (and water) than native plants van Helmont (1600’s) took tub with 200 lbs of must supplement with fertilizers soil and planted a 5 lb willow in it

after 5 years: eg. Nitrogen the willow weighed 164 lbs the soil weighed 2 oz in most plants, Nitrogen is absorbed as inorganic

minerals from the soil

much of global climate change is being caused by increasing amounts of CO2 in the however some plants are able to get their nitrogen in other ways: many oil and coal companies have touted the beneficial effects of CO2 on plant growth some plants can grow in N-poor soil using a eg. bristlecone pines and other native species have symbiosis with N-fixing that can shown enhanced growth over the past 50 extract N from the atmospshere and convert it years to a more useable form

what they ignore is that many other native species do

not benefit from increasing CO2 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 3 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 4 and in general weedy plants grow much better than do native plants with enhanced carbon dioxide levels

some plants are carnivorous and get their they are therefore (at least partially) nitrogen from digesting and other heterotrophic a few of these have completely given up ! tend to grow nitrogen poor soil photosynthesis

over 500 species have been described eg. parasitic plants

! N America has the most diverse 3000 species of parasitic plants

fauna largest group are the mistletoes (~800 sp)

most prefer damp boggy soils mostly tropical and subtropics

attract insects through , smell, but also includes:

indian paintbrush (a hemiparasite) a few plants not considered to be sandalwoods “carnivorous” may still be able to get at dodders (eg. Cuscuta sp.) of the morning glory family least some nutrition from them: broomrapes and figworts rafflesia

eg. petunias - covered with sticky hairs roots grow into host plant eg. potato, tobacco, rhododendron and teasel produce poisons that kill insects and may extract water, minerals and nutrients from absorb some nutrition from them vascular system of host

eg. a rare Brazilian plant produces underground leaves that trap, kill and absorb roundworms some have given up photosynthesis altogether and get all their organics from Heterotrophic Plants their host a few plants get at least some of their organic eg. dodder, coral orchid, broom rape, molecules in other ways than photosynthesis eg. pants parasitic on fungi

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 5 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 6

some plant roots parasitize the abundant fungi that grow in and on the forest floor eg. aspens tend to grow in large interconnected colonies and typically all members of the colony begin to show fall colors at the same time some of these have also completely lost the ability to do photosynthesis but some can also spread directly from tree to tree through these root grafts eg. snow plant

also produces its own heat that can actually eg. oak wilt often spread this way melt snow

a common method to control oak wilt is to trench Root Grafts around an infected tree one other way that perennial plants might get access ! breaks any root grafts with other

to both organic and inorganic foods are through Halophytes root grafts

so far we’ve talked about how plants get nutrients and as roots grow they encounter roots of other plants minerals when they are in short supply can be same or different species

under some situations plants have to deal with the may grow together to form graft opposite problem

root grafts are known for over 160 species of trees ! too many minerals and salts in the soil

eg. birch, maple, oaks, aspen if soil contains too many minerals; ie. is too salty the nutrients can pass between them plant may be unable to absorb water effectively

may be of advantage for a plant growing in poor soil that is connected to a plant nearby growing in good soil or near a ! salty soil can actually suck the water out of the creek or pond plant by osmosis (“water follows salts”) can also be exchanged most plants are fairly sensitive to high concentrations of salts in soil sometimes events like flowering or autumn colors in deciduous

plants are coordinated eg. too much fertilizer can kill a plant Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 7 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 8 ! aerobic respiration eg. farmland that is continually irrigated becomes less fertile as salts and minerals build up from evaporation since plants are much less active than animals they =soil salinization have a very low O2 requirement;

millions of acres of farmland have been removed from 1-2% is sufficient to maintain aerobic respiration cultivation because of salinization

!some O2 diffuses across cuticle and closed especially in dry climates stomata of leaves and herbaceous stems but a few plants can grow in high salt concentrations !in roots, well drained soil usually has enough air equivalent to the saltiness of sea water ~3% salt spaces to provide oxygen for roots these plants are called halophytes !when soil is saturated with water cells can use anaerobic respiration temporarily eg. many plants of the sea shore and salt marshes but cant grow and do normal metabolism halophytes have special cellular adaptations that until the soil drains

prevent them from taking up salt if soil remains flooded too long they will die

or !cypress & mangrove trees have adapted to living

in continuously saturated soil by producing allow them to secrete excess salt pneumatophores (“cypress knees”) which

eg. ( hairs) act like snorkels to bring O2 to the roots

Oxygen for Respiration in addition to needing oxygen atoms to build organic molecules plants also need oxygen molecules

(O2) to break down organic molecules for energy

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 9 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 10

Transport in Plants ! in one direction only most plants are large enough that they need some

way to be able to move materials around

the driving force of water movement in the xylem only the smallest plants lack a transport is the “pull” of system

the key to transpiration is the stomata of the leaves transport in plants is not like fluid transport in animals as water is evaporated from the stomata In most animals fluids are circulated in the body, usually using a muscular pump to push them along !tension is produced

Plants have no “muscle” cells – they have no pumps to resembling the “sucking” on a straw push fluids around !cohesion of water molecules “pulls” more water plants mainly use passive physical processes such up the plant to replace it as diffusion and osmosis to move things around water must form an unbroken of water There are two major transport systems found in most molecules for process to work plants: xylem a single bubble destroys the flow and stops transpiration phloem eg. cut , cut christmas trees A. Xylem Transport dissolved minerals are carried passively by the xylem is generally made of larger thicker-walled water cells that die at maturity to form long hollow ‘straws’ that extend and branch throughout the plant does not expend any energy the plant; from roots to leaves transpiration also helps to cool the plant water & minerals are absorbed by root hairs and mycorrhizae and are transported from the the only limit to how “high” a plant could draw roots to the stomata in the leaves water by transpiration depends : Plant Physiology - General, Ziser, Lecture Notes, 2012.10 11 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 12 stomata are usually open in the !the cohesion of water molecules, daytime and closed at night !the diameter of the “straws” (xylem cells), !the pull of gravity, and !the weight of water wilting = too much transpiration

eg. biologists have calculated that transpiration stomata will close should be able to pull water up “pipes” as long as remain closed until water is available 450’ (=150 m) local environmental variations can affect water the tallest trees on earth are 375’ loss & trigger opening and closing of stomata how tall could a tree get on the moon? mars? 1. high

transpiration requires lots of water 10º C increase doubles rate of evaporation

99% of all water taken up by plants ends up in 2. high

the atmosphere hot windy days increase transpiration and cause water stress in plants ! the water is used to get a small amount of water and minerals to leaves for metabolism 3. low

eg. 1 corn plant ! 52 gallons/season eg. Houseplants are usually tropical in origin: have large leaves, open exposed stomata eg. on a warm day a maple tree may lose 50-60 gallons/hour no adaptations for conserving water

eg. an acre of temperate forest transpires ~8000 these plants may spend most of their time with gallons/day closed stomata and little growth

stomata can be open or closed by the action of watering heavily doesn’t solve problem unless two guard cells that surround each pore done correctly

!need to water entire root zone transpiration only occurs when the stomata are open: otherwise new growth areas will die

more houseplants are killed by overwatering than underwatering Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 13 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 14

6. narrow needlelike leaves or rolled leaves

4. low CO2 reduce surface area for evaporation

! stomata open even after dark eg. conifers

5. water stress B. Phloem Transport

! stomata closed even in daytime phloem is composed of living cells joined end to 6. end

! internal clock; stomata open and close at same time each day phloem generally moves organic molecules such as sugars, hormones, secondary plant in many habitats or certain seasons, water can compounds, etc throughout the plant become limited in phloem, materials can move in any direction !some plants have evolved many adaptations = translocation to conserve water in some plants glucose and fructose are combined to 1. desert plants, eg cacti, have changed their make sucrose which is then transported in phloem physiology so that stomata are open at night and closed during the day eg. sugar cane, sugar beets, maple

2. succulents store scarce water in leaves or movement of sugar in phloem stems

3. desert & cold climate plants often have much is partly by passive diffusion of materials thicker cuticles down a concentration gradient

1-3% of water can be lost through moves from areas high in sugar (leaves)

to areas low in sugar (eg. roots, stem) 4. some plants lack stomata on top of leaves,

only have them on protected side eg. new growing

5. sunken stomata or thick leaf hairs and partly an active process that requires not as exposed to air currents energy

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 15 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 16 sugars are actively moved from cell to cell or Plant Behaviors concentrated in certain plant parts

translocation in phloem is much slower than most regard plants as completely unresponsive transpiration in xylem organisms

[6-22’/hr in phloem vs 500’/hr in xylem] however, more and more we find plants capable of some pretty complex activities that, in animals, we would call “behaviors”

some common plant behaviors:

a. plant movements

b. control in plants

c. parasitic plants “pursuing” hosts

d. plants fighting each other for resources

e. plant defensive behaviors

A. Plant Movements

while plants are generally unable to move about as individuals; like all living organisms they are capable of at least some simple forms of movements:

three general kinds of movement in plants: a. simple movements (=) b. rapid leaf movements

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 17 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 18

c. cyclic plant movements produced by specialized cells that form a hingelike area (=pulvinus) at the base of two leaves or leaflets

A. Simple Movements (Plant Tropisms) when stimulated by touch, electricity or chemicals causes and water to quickly leave cells = any permanent change in position of a plant or a part of a plant ! leaf wilts and folds

we’ve already discussed some tropisms: recovery takes considerably longer than original response and geotropism C. Cyclic Plant Movements also slower than rapid movements and occur ! response to mechanical stimuli repeatedly over some kind of cycle eg. twining of tentrils eg Solar Tracking other tropisms can be cause by water, temperature, chemicals and oxygen for leaves or flowers it allows maximal exposure to light for photosynthesis B. Rapid Leaf Movements eg. sunflowers, soybeans, cotton eg. sensitive plant is a slower but probably similar mechanism to ! folds leaves and droops in response to touch, electrical or chemical stimuli rapid movements

eg. eg. “sleep” movements

! captures insects day – leaves are horizontal

very rapid response night – they fold up or down

can spread throughout plant

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 19 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 20 B. Temperature Control (“warm blooded” eg. philodendron can maintain a temperature of 46º C plants?) even in 4º weather the temperature of most plants reflects the ! to enhance pollenation temperature of their surroundings eg. plants in arum family generate heat to attract flies for pollenation but some plants are able to generate relatively large amounts of heat eg. voodoo lily (Sauromatum guttatum) parts of heat up to vaporize and disperse attractants for pollenators they can turn this ability on and off C. Parasitic Plants “pursuing” Hosts eg. some generate heat in late winter/early spring

plants produce heat much more efficiently than do animals (ie. all the parasitic plants such as dodder are able to follow a energy extracted from food by the mitochondria is converted to “scent trail” to find their host heat; in animals only about 40% is converted to heat, the rest into ATP ! they grow toward host some plants generate this heat by burning fat just like animals D. Plants Competing for Resources this heat is used in several ways:

some plants, often desert plants or where ! so plant can get a jump on the growing season resources are scarce secrete chemicals into

eg. skunk cabbage (Symplocarpus foetidus; arum family) the soil to prevent other plants from growing can maintain temperature of 16-24º C in all nearby weather can even melt snow eg. creosote bush generates heat by burning in special cells

eg. Blue moonwort of Swiss Alps (primrose fam) E. Plant Defenses & Defensive autumn develops thick leathery leaves that lie flat on Behaviors ground covered by snow to depth of several feet in spring melting snow trickles to plant plants must defend themselves from a variety of generates heat that further melts snow

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 21 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 22

pests: birds, insects, mammals, fungi, , plants produce 1000’s of chemicals that are used for bacteria, roundworms protection and defense

>200 known bacterial diseases of plants eg. Alkaloids (N containing cmpds) & Tannins

! symptoms: soft rots, leaf spots, blights, wilts, galls very bitter tasting chemicals >7600 viral plant diseases known alkaloids ! symptoms: stunted growth, leaf deformities, tumors

eg. nicotine, caffeine, quinine >2000 species of parasitic roundworms as well as other

parasites tannins !usually attack roots eg. taste of tea, tartness of persimmons, >millions of herbivorous animals, especially insects and some of the flavor of certain mammals that feed on plants most of these chemicals seem to be poisonous since plants can’t actively avoid such confrontations or even fatal to animals if ingested they have developed a wide variety of mechanical and chemical defenses to protect themselves both fungi and plants produce these compounds but mainly in only a few plant families Mechanical Defenses animals cannot make them

eg. spines, hairs, tough surfaces, thorns, prickles, plants produce alkaloids that protect them coat, etc against and

eg. some grasses have silica crystals in leaves to eg. poison ivy, nightshade

deter herbivores alkaloids are often localized in specific plant

causes cuts in humans parts

Plant Defensive Chemicals eg. potato plants: leaves, and skins of tubers (if exposed to light)

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 23 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 24 in potatoes some are concentrated in the skin of defensive chemical that helps prevent fungal the potato infections and damage

most are usually removed by peeling eg. Capsaicum !cooking potatoes in their skin may cause these chemicals to move into the “flesh’ of the potato capsaicum (give peppers their ) inhibits herbivorous mammals from eating the ! don’t eat raw potato skins if on inside

[Application] in small doses, some alkaloids have medicinal prevents certain fungi from infecting its properties eg. Some Protective 1000’s of prescription and OTC medication

some are addictive &/or hallucinogenic in humans some plants produce proteins that inhibit digestion in insect gut and therefore eg. nicotine, cocaine, heroin cause the animal to eat less or to move to another plant

eg. many crop plants damaged by feeding insects send a [Application] message throughout the plant causing it to synthesize tannins are widely used as stains, , inks or tanning proteins that inhibit digestion in the gut of the insect agents for leather

may be a link between high levels of exposure to certain some plant chemicals are used to communicate to tannins in foods and the workplace and some forms of other plants of the same species cancer eg. corn plants release a volatile chemical when being eaten by but people who drink large amounts of green tea may caterpillars that attracts predatory wasps that parasitize the be more protected from cancer due to other kinds of caterpillars that feed on them tannins plants can also detect chemicals produced by nearby eg. Resins herbivores

mainly produced by conifers ! triggers them to produce more alkaloids to make leaves less palatable Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 25 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 26

Plant Hormones virtually all multicellular produces hormones to help coordinate and control growth, , many of the plant activities above are regulated by and development hormones multicellular fungi, simple plants and simple animals

that lack an elaborate transport system = chemical produced in one tissue or ! chemicals diffuse from cell to cell has its effect in another tissue or organ (=target

cell or organ) or maybe carried by water if aquatic to other cells

in same individual since plants are relatively large & complex they also

need to have some way to coordinate and control organisms with vascular systems, higher plants and these activities animals transport chemicals in fluid

in plants ! phloem !make sure activities throughout the plant are in animals ! circulatory system timed properly only animals have a nervous system as an additional method of coordination and control activities of complex organisms (plants & animals) can be coordinated by Major Plant Hormones:

A. !nerve impulses (only in animals) B.

! hormones (found in all kingdoms) C. D. chemical controls is a common feature of all E. Abscissic Acid

organisms A. Auxins

single celled organisms secrete chemicals that affect their environment and each other Auxins are a group of hormones that regulate growth in many parts of a plant eg. bacteria !colonial species ! attraction eg. mating ! Paramecium 1st identified eg. repelling BG bacteria !

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 27 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 28 discovered by Charles Darwin and son, 1880 others become quite bushy

growth in ‘non-bushy’ plants occurs mostly from apical they noticed that plant on windowsill bends rather than axillary buds = apical toward light dominance

auxins produced in apical meristem inhibit they shielded tip of canary grass seedlings from light development of axillary buds ! no bending occurred

eg. pruning, pinching when tip was removed

! no bending snip off apical to get branching

when bottom of was shielded ! shoot still bent toward light 4. stimulates fruit development

conclusion: some influence is transmitted from the the growth and development of the of a flower into a upper to the lower part of the plant causing it to fruit are controlled by auxins produced after the flower bend has been pollinated: today we have identified several important when unpollenated flowers are treated with auxins: ovary enlarges and becomes a seedless fruit functions of auxins: eg. tomatoes, watermelons, peppers, strawberries 1. promotes phototropism 5. leaf (& fruit drop) ! stems () bend toward light (=phototropism) the loss of leaves or dropping of ripe fruit depend on 2. promotes geotropism changing levels of auxins on each side of the “abscission zone” at the base of the leaf or fruit ! roots bends downward toward ground (away from light) (=geotropism) eg. in leaves higher levels (in leaf vs stem) promote loss of leaves has inhibitory effect on “down” side of root eg. in fruits lower auxin levels (in fruit vs stem) cause 3. promotes fruit drop

eg. artificially applied auxins to fruit (=growth of a single main stem or trunk)

!delay fruit drop and produce larger fruits some plants tend to branch out very little as they grow,

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 29 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 30

eg. synthetic auxins are used as herbicide/defoliant for 1. promotes stem elongation broadleaved plants (doesn’t kill grasses – don’t know why) causes sudden & excessive lengthening of stem

many of the worlds most important crops are grasses: eg. when biennial plants such as lettuce and cabbages, eg. wheat, corn, rice or yuccas, century plant send up long flower stalks(=bolt) these herbicides are used to kill weeds that compete with these crops in the fields dwarf plants such as in sub arctic, lack gibberellins

eg. 2,4-D; Agent Orange ! when is added they grow to normal during Vietnam war they were used to defoliate large heights areas to expose hiding places of enemy and to destroy their crops eg. most grape growers spray with gibberellins to increase length of branches between fruit clusters a. the dioxin in the mix was later found to cause: (more air, fewer fungal infections) >health problems >incidence of some forms of cancer ! produces larger, healthier grapes >birth defects and stillbirths b. over a third of the commercial and natural 2. gibberellins may also be involved in plant forests and 1000’s of acres of farmland were destroyed movements and flowering

6. promotes adventitious root development C.

auxins also control the developmentof adventitious roots produced in roots and move throughout the plant ! treating stem with auxins promotes root development 1. promote cell division & differentiation

eg. root stimulators are synthetic auxins used to they must be present in cells for them to divide stimulate root development on cuttings for asexual propagation !plant cells grown in culture without it will enlarge enormously but will not divide until cytokines are added B. Gibberellins

2. delays senescence & aging gibberellins are produced mainly in developing leaves, shoots, roots and seeds plants receive a continuous supply of cytokines from roots

! when cut they age and die rapidly Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 31 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 32 !a mutant corn unable to make abscissic acid eg. if sprayed on cut leaves and stems they will remain germinates on the ear green longer while unsprayed leaves will turn yellow and die spring rains wash out the abscissic acid allowing seed to germinate D. Ethylene eg. soak seeds before planting

a gas 3. acts as plant stress hormone

1. promotes fruit protects cells from drought, freezing, salination

as fruit ripens it produces ethylene which accelerates the process

eg. “one rotten apple spoils the lot”

eg. black spots on bananas are spots of ethylene production

ethylene is used commercially to promote uniform ripening in bananas that are picked while green (longer shelf life)

E. Abscissic Acid

[does NOT induce abscission]

1. promotes in woody stems

as winter approaches, woody plants cease growth and develope protective bud scales under influence of abscissic acid

2. promotes seed dormancy

seeds have a high concentration of abscissic acid and cannot germinate until these levels are reduced

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 33 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 34

Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 35 Plants: Plant Physiology - General, Ziser, Lecture Notes, 2012.10 36