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Plant Anatomy AP Biology 2006-2007 Basic plant anatomy 1 root AP Biology root tip root hairs 1 Roots Roots anchor plant in soil, absorb minerals & water, & store food fibrous roots (1) mat of thin roots that spread out monocots tap roots (2) 1 large vertical root also produces many small lateral, or branch roots dicots root hairs (3) 2 increase absorptive surface area AP Biology 3 Basic plant anatomy 2 root - - fungi at tips of the roots Mycorrhizae -Symbiotic relationship shoot (stem) buds terminal or apical buds-located at the top axillary buds-located at the V formed b/t leaf and stem AP Biology Modified shoots stolons (strawberries) AP Biology tuber (potato) rhizome (ginger) bulb (onion) Leaves Function of leaves photosynthesis energy production CHO production gas exchange transpiration AP Biology simple vs. compound AP Biology Putting it all together Obtaining raw materials sunlight leaves = solar collectors CO2 stomates = gas exchange H2O uptake from roots nutrients uptake from roots AP Biology Plant TISSUES Dermal epidermis (“skin” of plant) single layer of tightly packed cells that covers & protects plant Ground bulk of plant tissue photosynthetic mesophyll, storage Vascular AP Biology transport system in shoots & roots xylem & phloem Plant CELL types in plant tissues Parenchyma “typical” plant cells = least specialized photosynthetic cells, storage cells tissue of leaves, stem, fruit, storage roots Collenchyma unevenly thickened primary walls support Sclerenchyma AP Biology very thick, “woody” secondary walls support rigid cells that can’t elongate dead at functional maturity If I’d only had triplets! Xylem and Phloem Xylem- water conducting cells. xylem vessels- found mostly in angiosperms have pits for water movement. xylem tracheids- long thin cells strengthen with lignin AP Biology vessel elements Xylem vessel element Vascular tissue move water & minerals up from roots dead cells at functional maturity only cell walls remain need empty pipes to efficiently move H2O transpirational pull dead cells Aaaah… Structure–Function again! tracheids AP Biology Phloem: food-conducting cells carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata AP Biology living cells Phloem: food-conducting cells sieve tube elements & companion cells AP Biology Phloem Aaaah… Structure–Function again! Living cells at functional maturity cell membrane, cytoplasm control of diffusion lose their nucleus, ribosomes & vacuole more room for specialized transport of liquid food (sucrose) Cells sieve tubes sieve plates — end walls — have pores to facilitate flow of fluid between cells companion cells nucleated cells connected to the sieve-tube help sieve tubes AP Biology Plant Growth Chapter 35 AP Biology 2006-2007 Life Cycle of Plants Annuals- in one year Ex:Wildflowers, crops Biennials- completed in 2 years Ex: radishes and carrots Perennials- continues for many years Ex. Trees AP Biology Growth in Plants Specific regions of growth: meristems stem cells: perpetually embryonic tissue regenerate new cells apical shoot meristem growth in length primary growth apical root meristem growth in length primary growth lateral meristem growth in girth secondary growth AP Biology Apical meristems AP Biology shoot root Root structure & growth AP Biology protecting the meristem Shoot growth protecting the meristem Young leaf primordium Apical meristem Older leaf primordium Lateral bud primordium AP Biology Vascular tissue Primary xylem Growth in woody plants Woody plants grow in height Primary phloem from tip Epidermis Lateral meristems primary growth apical meristem Woody plants grow in diameter from sides secondary growth lateral meristems Primary phloem vascular cambium makes 2° phloem & 2° xylem cork cambium makes bark AP Biology Annual growth layers Secondary phloem Secondary Primary xylem xylem Bark Vascular cambium Why are early & late growth different? Phloem produced to the outside Xylem produced to the inside bark cork cambium phloem xylem vascular cambium AP Biology late early last year’s xylem cork cambium Woody stem How old is this tree? vascular cambium late early 3 2 1 xylem phloem AP Biology bark Secondary Growth produced by the vascular cambium Vascular cambium Growth X X C P P X X C P Vascular cambium Secondary xylem Secondary phloem X C P C X C C C AP Biology After one year of growth After two years of growth Plant hormones Ch:39 auxin gibberellins abscisic acid ethylene and more… AP Biology Auxin (IAA) Effects controls cell division & differentiation phototropism growth towards light asymmetrical distribution of auxin cells on darker side elongate faster than cells on brighter side AP Biology apical dominance Gibberellins Family of hormones over 100 different gibberellins identified Effects stem elongation fruit growth seed germination AP Biology plump grapes in grocery stores have been treated with gibberellin hormones while on the vine Abscisic acid (ABA) Effects slows growth seed dormancy high concentrations of abscisic acid germination only after ABA is inactivated or leeched out survival value: seed will germinate only under optimal conditions light, temperature, moisture AP Biology Ethylene Hormone gas released by plant cells Effects fruit ripening leaf drop like in Autumn apoptosis One bad apple spoils the whole bunch… AP Biology Fruit ripening Adaptation hard, tart fruit protects developing seed from herbivores ripe, sweet, soft fruit attracts animals to disperse seed Mechanism triggers ripening process breakdown of cell wall softening conversion of starch to sugar sweetening positive feedback system ethylene triggers ripening ripening stimulates more ethylene production AP Biology Apoptosis in plants Many events in plants involve apoptosis response to hormones ethylene auxin death of annual plant after flowering senescence differentiation of xylem vessels loss of cytoplasm AP Biology shedding of autumn leaves What is the evolutionary advantage of loss of leaves in autumn?