W8L1 - Plant structure

W8L1 - Plant structure - Biol 5B Organismal Biology Spring...

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1 Biol 5B: Organismal Biology Spring ’09 WEEK 8; Lecture 1 Plant structure Developmental plasticity : the ability to alter form in response to its environment
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2 Plasticity • Developmental plasticity is more marked in plants than in animals • In addition to plasticity, plant species have by natural selection accumulated adaptations in morphology Plant organs • The three basic plant organs: roots, stems, and leaves • Morphology reflects their evolution as organisms that draw nutrients from below and above ground • They are organized into a root system and a shoot system • Roots rely on sugar produced by photosynthesis in the shoot system, and shoots rely on water and minerals absorbed by the root system
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3 Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Leaf Blade Petiole Axillary bud Stem Taproot Lateral branch roots Root system Roots Roots are multicellular organs with important functions: – Anchoring the plant – Absorbing minerals and water – Storing organic nutrients
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4 Roots A taproot system consists of one main vertical root that gives rise to lateral roots , or branch roots Adventitious roots arise from stems or leaves Seedless vascular plants and monocots have a fibrous root system characterized by thin lateral roots with no main root Root hairs In most plants, absorption of water and minerals occurs near the root hairs Vast numbers of tiny root hairs increase the surface area
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5 Prop roots “Strangling” aerial roots Storage roots Buttress roots Pneumatophores Aerial roots that support tall, top- heavy plants Food and water stored in roots Seeds germinate in branches; host tree dies Air roots: enable root system to obtain oxygen Aerial roots support tall trunks Stems •A stem is an organ consisting of – An alternating system of nodes , the points at which leaves are attached Internodes , the stem segments between nodes Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Leaf Blade Petiole Axillary bud Stem Taproot Lateral branch roots Root system
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W8L1 - Plant structure - Biol 5B Organismal Biology Spring...

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