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The Shoot: Primary Structure and Development Chapter 25
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True or False 1)Shoots contain stems and leaves. 2)Shoots are the above ground portion of the plant and are anatomically the same as roots.
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The Shoot Shoot- the above ground portion of the plant, consisting of stem and leaves. –Stem- the above ground axis of vascular plants. –Leaf- the principle lateral appendage of the stem. Foliage leaf- photosynthetic organ. Node- the part of the stem where one or more leaves are attached. Internode- the region of the stem between two successive nodes. Bud- an embryonic shoot protected by young leaves.
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Primordium- a leaf or bud in its earliest stage of differentiation.
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Pith- the ground tissue occupying the center of a root or shoot.
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Basswood Alfalfa Corn
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Modified Stems Tendrils- modified leaves that spirally coil and aid in stem support. Stolons- runners; stems that grow horizontally on the soil surface, often giving rise to new plants at the nodes. Thorns- hard, woody, sharp-pointed modified stems, arise from the axils of leaves. Spines- hard, woody, sharp-pointed modified leaves or leaf-parts. Prickles- a small non-woody, sharp-pointed outgrowth of bark or the epidermis.
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True or False. This is a tendril.
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True or False. This is also a tendril.
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Given: the following is a hard, woody, sharp-pointed modified stem that arises from the axils of leaves. True or False. This is a spine.
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Spines
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Prickles
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Underground Stems Rhizome- a horizontal stem that grows at or below the soil surface. Tuber- an enlarged, short, fleshy underground stem, forms at the tip of a rhizome. i.e. Potato. Bulb- a shortened underground stem covered by enlarged fleshy storage leaves. i.e. Onion and garlic. Corm- a thickened underground stem with small papery leaves. i.e. Gladiolus and Crocus.
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Leaf Arrangement Phyllotaxy- the arrangement of leaves on a stem. –Basal- leaves are attached to an underground stem or rhizome. –Opposite- 2 leaves attached at each node, borne on opposite sides of the stem. –Alternate- 1 leaf attached at each node. –Whorled- 3 or more leaves at each node. Basal
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Leaf Morphology Blade- lamina. Petiole- stalklike portion. Stipules- scalelike or leaflike appendages at the base of leaves. Simple vs. Compound Leaves –Simple- blades undivided. –Compound- blades divided into leaflets. Pinnately compound- leaflets arising from both sides of the axis. Palmately compound- leaflets diverge from the tip of the petiole.
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Leaf Histology Mesophyll- the ground tissue of the leaf, specialized for photosynthesis. –Palisade parenchyma- upper cells. –Spongy parenchyma- lower cells.
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Hydrophyte- waterlily.Xerophyte- oleander.
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Eudicot- random stomata.Monocot- parallel stomata.
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Leaf Abscission Abscission- the normal separation of the leaf from the stem. Structural and chemical (ethylene) changes result in the formation of an abscission zone: –Separation layer –Protective layer Magnesium ions, sugars, amino acids.
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