Plant Development - Module 2: Growth & Reproduction Or,...

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Or, How do multicellular organisms get bigger, and then make copies of themselves
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Plant Development: Communal Living by Cells Key Concepts The plant body has a hierarchy of organs, tissues and cells Meristems generate new cells for new organs Primary growth lengthens shoots and roots Secondary growth adds girth to Growth, morphogenesis, and differentiation produce the plant body
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The Three Basic Plant Organs: Roots, Stems, and Leaves The basic morphology of vascular plants Reflects their evolutionary history as terrestrial organisms that draw nutrients from two very different environments: below-ground and above- ground Three basic organs evolved: roots, stems, and leaves They are organized into a root system and a shoot system Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Vegetative shoot Blade Petiole Stem Leaf Taproot Lateral roots Root system Shoot system Axillary bud Flowers are leaves specialized for reproduction Stems & leaves
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Roots A root Is an organ that anchors the vascular plant Absorbs minerals and water. In most plants absorption of water and minerals occurs near the root tips, where vast numbers of tiny root hairs increase the surface area of the root Often stores organic nutrients Taproot system Fibrous system Root hairs
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Prop roots. Modified roots Storage roots. “Strangling” aerial roots. Buttress roots. Pneumatophores
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Stems A stem is an organ consisting of an alternating system Nodes are points at which leaves are attached Internodes, the stem segments between nodes Bud = embryonic shoot but can also form flowers (with proper chemical cues) An axillary (lateral bud) can develop into another stem/ branch A terminal bud (apical bud) is located at the tip of the stem or branch and causes elongation of a young shoot
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Stems and Modified Stems Potato tuber is a stem, ‘eyes’ are lateral buds, a sprouting potato is a branching stem Runners of strawberry plants are horizontal stems from which roots can form, if connections along runner broken, independent plants can develop (an example of vegetative reproduction) Stems of barrel cactus are enlarged to store water. Bulbs are vertical, underground shoots consisting mostly of the enlarged bases of leaves that store food.
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Vegetative Organs of the Flowering Plant Body - Leaves Leaves are responsible for most photosynthesis Generally consist of a flattened blade and a stalk called a petiole that joins the leaf to a node of the stem Flat blades of leaves, held perpendicular to the sun’s rays. Some leaves track the sun
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Axillary bud Petiole Leaflet Axillary bud Petiole Leaf morphology simple leaf Axillary bud Petiole Leaflet compound leaf doubly compound leaf
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_______ Modified leaves Spines. Storage leaves.
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Plant Development - Module 2: Growth & Reproduction Or,...

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