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Evolution of Plants

Ch 29-30

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Plants multicellular, photosynthetic

autotroph and eukaryotic cell walls made of cellulose,

starch is storage Land based take up water via capillary

action from the ground have alternation of

generation

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Evolution of Plants – p.602-603

Major adaptations for land survival 1) Except for Bryophytes (moss), dominant

generation is the diploid sporophyte generation, so? this masks mutations, greater survival

2) Cuticle = waxy covering, p.604, so?reduce water loss

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3) Vascular system → p.612reduced dependency on water (store it) so it can

be farther away from it, tissue specialization

4) Evolution of pollen & seeds (from spores)- ability to move in the air (vs. water), p.620

5) In Anthophyta - gametophytes→ gametes enclosed & protected in an ovary, p.626

6) Conifers and Anthophyta have developed adaptations to seasonal variations in availability of water and light → ex. Deciduous trees

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Divisions– (division is after kingdom, before phylum) 0) Charophytes (green algae) - precursor of plants, how know? 4 reasons, p.600

rosette-shaped cellulose-synthesizing complexes peroxisome enzymes structure of flagellated sperm formation of phragmoplast

1) Bryophytes - simplest plants, no true stems or leaves, can't live far from water or grow tall

Repro. in water, antheridia (male) and archegonia (female) gametophyte is dominant generation, p.607 ex. moss, hornworts, liverworts, p.608

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2) Tracheophytes/Pteridophytes – seedless, vascular xylem (water up) and phloem (sugar), p.614 roots, hairs sporophyte is dominant, makes spores, ex. ferns3) Gymnosperms - "naked seed” or pollen replaced the spore,

better dispersal, *p.622-623 cone bearing = conifers, includes cycads and ginkgo increased vascular tissue, ex. evergreens, spruce, pine4) Angiosperms - flowering plants, p.630-631, life cycle p.629

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Flower petals, sepals attract pollinators Stamen – male parts

Anther – produces pollen or microspores

Filament – holds the anther Pistil – female parts (carpel(s))

Stigma – sticky, capture pollen Style – long tube, connects stigma and ovary Ovary – where fertilization occurs, ovules are here, eggs are

called megaspores, fruit here ovary develops into a fruit, disperses seeds by insects, birds and mammals – coevolution →plants use for medicines, wood and food

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Plant Structure and Growth- structure and function Ch 35-39

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Angiosperm - flowering plants

2 classes: 1) Monocots- 1 cotyledon (storage

seed), parallel veins, complex vascular bundle, floral parts in groups of 3's

2) Dicots - 2 cotyledons, web-like veins, vascular tissue in a circle, taproots, floral parts in 4's or 5's

Plant Tissues Dermal – protective

cover (water loss and disease)

Ground – metabolic functions

Vascular – transports materials between root and shoots systems

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Types of plant cells- p744

Protoplast – contents inside the cell wall1) Parenchyma – unspecialized cells, most metabolic

functions2) Collenchyma- most growing cells, elongate stems,

support3) Sclerenchyma- don’t grow, very strong, some are

dead, strengthened by lignin (p.612)

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Types of plant cells (con’t)- p.745

Vascular system4) Xylem - water & minerals up the plant,

made of tubes called tracheids and vessel elements, dead at functional maturity

5) Phloem - food up and down to the plant, made of sieve tubes, alive, but reduced organelles to speed up transport

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Root system

Roots = anchor, absorb, storage taproot – 1 large root, strong and

large, ex. carrot fibrous root – has extensions called

root hairs, increases SA

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Shoot system

= Stems and Leaves Stem – attachment of

leaves, similar structure to roots

Leaves – photosynthetic organ

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Plant Growth = Germination seeds remain dormant until a cue (ex. water, light

or temp.)= photoperiod 1st growth occurs when water is absorbed, seed

coat cracks Seeds – contain the embryo and storage material the top of the embryo produces a shoot Indeterminate Growth – grow throughout life, p.746

Annual – complete entire life cycle in 1 year or less Biennial – need 2 growing seasons to complete life cycle Perennial – live many years

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growth occurs at the tips of roots and shoots called apical meristem = meristematic tissue

3 zones of growth zone of cell division - newly dividing

cells zone of elongation- new cell growth zone of differentiation - cells

differentiate

Primary Growth

Secondary Growth Also lateral meristems = cylinders of dividing cells that

increase the girth (width) of stems and roots Vascular cambium – adds vascular tissue called

secondary xylem (wood) and secondary phloem Cork cambium – replaces the epidermis with thicker,

tougher layer

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Leaves photosynthetic organ made of blade (end), and petiole (connects the stem) 1) epidermis

Cuticle- waxy layer, holds in water2) palisade mesophyll- many parenchyma cells and

chloroplasts, photosynthesis3) spongy mesophyll - space for CO2 and O2

contains vein = xylem and phloem4) Lower epidermis- bottom layer

Stomata- opening for gas exchange Guard cells – surround stoma, control their opening

Modifications – see page 742, protection, water storage

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Transport of water & sugar

Ch 36

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Water absorbed in roots and

passes up the xylem also moves through

the cell wall or plasmodesmata

Short distance flow, p.773 – regulated by Casparian strip

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3 mechanisms

1) Osmosis moves into roots, then into xylem high mineral gradient inside

= root (turgor) pressure chemiosmosis, proton pumps

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2) Capillary action – movement by adhesion Adhesion – water "sticks" to sides of the tubes

3) Transpiration-Cohesion-Tension theory – most water moves this way, water potential

transpiration (bulk flow)– evaporation of water from the leaves, lower [water] in the leaves, so water goes up, works by negative pressure, p.774

cohesion – attraction of water molecules

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Control of the Stomata

regulates amount of CO2 , O2 and H2O aids in control of photosynthesis the guard cells control opening of stomata light, CO2 depletion in leaves, high temps,

and circadian rhythms regulate opening

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Sugar, p.779 Translocation = movement of

sugar through the phloem source/sink – sugar moves from

the source of sugar (leaf) to the place where it is used = sink

pressure flow – high solute at source→ lowers water potential →water into sieve tubes→ causes lower pressure at sink →the pressure difference moves sugar through

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Nutrition

Ch 37

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soil, water, nitrogen, minerals

Rhizobacteria, p.793

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Mycorrhizae, p.767

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Life cycle of plants

Ch 38

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Alternation of generation

Gametophyte – haploid(n) generation, produces haploid gametes by mitosis

gametes then combine to form a diploid plant protected within the sporophyte plant Sporophyte – diploid(2n) part, makes haploid

spores by meiosis →In bryophytes gametopyte is dominant →In others, sporophyte is dominant

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Cycle p.802 1)  spores (n) develop from the sporophyte plant 2)  spores form gametophyte (n) part of plant 3)  gametophyte forms gametes(n) 4)  gametes combine (fertilization) to form zygote (2n) mitosis, develop into mature sporophyte (2n), back to 1

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Double Fertilization

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Plant controls

Ch 39

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Plant Hormones

Auxin – made at apical meristem or embryo, elongation of stem, root growth, fruit growth

Gibberellins – made at meristems, growth in young parts, flowering, leaf growth, excess can cause bolting, germination

Cytokinins – stimulate cell division and differentiation, growth of lateral buds, slows leaf aging

Ethylene gas– ripening of fruit, stimulates flower growth Abscisic acid – inhibits growth, closes stomata, aids

dormancy

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1) gravitrophism – response to gravity, p.841

2) thigmotrophism – response to touch, p.842

3) phototropism –response to light, auxin is made →plant grows, stem bends toward light because auxin collects on shady side

Plant stimuli = tropisms

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Photoperiodism

response to a change in the photoperiod or length of daylight

this is circadian rhythm of a plant (internal clock) controlled and reset by proteins called phytochromes night light is responsible for resetting the internal

clock

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3 types of plants based on light – p839 1) long day plants – (short night) flower in the

spring when night is shorter than a critical night period

2) short day plants – (long night) flower in late summer, early fall, when night exceeds a critical dark period

3) day neutral – plants don’t respond to daylight changes, flowering triggered by temp. or water amount

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