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Evolution of Plants Ch 29-30 5/8/2017 1 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 5/8/2017 2 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 5/8/2017 water loss 3 3) Vascular system → p.612 reduced 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 5/8/2017 4 5/8/2017 5 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 5/8/2017 6 2) Tracheophytes/Pteridophytes – seedless, vascular xylem (water up) and phloem (sugar), p.614 roots, hairs sporophyte is dominant, makes spores, ex. ferns 3) 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, pine 4) Angiosperms - flowering plants, p.630-631, life cycle p.629 5/8/2017 7 5/8/2017 8 5/8/2017 9 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 5/8/2017 10 5/8/2017 11 Plant Structure and Growth- structure and function Ch 35-39 5/8/2017 12 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 5/8/2017 13 Plant Tissues Dermal – protective cover (water loss and disease) Ground – metabolic functions Vascular – transports materials between root and shoots systems 5/8/2017 14 Types of plant cells- p744 Protoplast – contents inside the cell wall 1) Parenchyma – unspecialized cells, most metabolic functions 2) Collenchyma- most growing cells, elongate stems, support 3) Sclerenchyma- don’t grow, very strong, some are dead, strengthened by lignin (p.612) 5/8/2017 15 Types of plant cells (con’t)- p.745 Vascular system 4) 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 5/8/2017 16 Root system Roots = anchor, absorb, storage taproot – 1 large root, strong and large, ex. carrot fibrous root – has extensions called root hairs, increases SA 5/8/2017 17 Shoot system = Stems and Leaves Stem – attachment of leaves, similar structure to roots Leaves – photosynthetic organ 5/8/2017 18 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 – complete entire life cycle in 1 year or less Biennial – need 2 growing seasons to complete life cycle Perennial – live many years Annual 5/8/2017 19 Primary Growth 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 5/8/2017 20 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 5/8/2017 21 5/8/2017 22 Leaves photosynthetic organ made of blade (end), and petiole (connects the stem) 1) epidermis Cuticle- waxy layer, holds in water 2) palisade mesophyll- many parenchyma cells and chloroplasts, photosynthesis 3) spongy mesophyll - space for CO2 and O2 contains vein = xylem and phloem 4) Lower epidermis- bottom layer Stomata- opening for gas exchange Guard cells – surround stoma, control their opening Modifications – see page 742, protection, water storage 5/8/2017 23 5/8/2017 24 5/8/2017 25 Transport of water & sugar Ch 36 5/8/2017 26 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 5/8/2017 27 3 mechanisms 1) Osmosis moves into roots, then into xylem high mineral gradient inside = root (turgor) pressure chemiosmosis, proton pumps 5/8/2017 28 5/8/2017 29 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 5/8/2017 30 5/8/2017 31 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 5/8/2017 32 5/8/2017 33 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 5/8/2017 34 Nutrition Ch 37 5/8/2017 35 soil, water, nitrogen, minerals 5/8/2017 36 Rhizobacteria, p.793 5/8/2017 37 Mycorrhizae, p.767 5/8/2017 38 Life cycle of plants Ch 38 5/8/2017 39 Alternation of generation 5/8/2017 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 40 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 5/8/2017 41 5/8/2017 42 5/8/2017 43 Double Fertilization 5/8/2017 44 5/8/2017 45 5/8/2017 46 Plant controls Ch 39 5/8/2017 47 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 5/8/2017 48 5/8/2017 49 Plant stimuli = tropisms 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 5/8/2017 50 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 5/8/2017 51 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 5/8/2017 52 5/8/2017 53