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植物学及园艺学英文版 botany and horticulture (84).ppt

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植物学及园艺学英文版 botany and horticulture (84).ppt
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Lecture 13: Leaves,Review of Leaf Structure,What We’ll Cover (Chapter 11 of book),Review of external leaf structure Structure and function of leaf tissues Leaf Transpiration and exchange of gases How water moves through plants Senescence Specialized functions in leaves Human uses for leaves Review Questions pp. 208, #1-10,Sessile Leaves Have No Petioles,Monocot Leaves Possess a Sheath,Simple Leaves,Compound Leaves,Patterns of Veins in Leaves : Monocots,Patterns of Veins in Leaves: Dicots,Leaf Arrangement,Leaves Adapt to their Environment,Determine the specific structure and organization of tissues Hydrophytes – adapt to live partially or wholly submerged in water Xerophytes – Adapt to live with little or no water Mesophytes – Adapt to live in a moist climate,4 Main Tissues of the Leaf,Epidermis – rigid outer layer, protects inner layer and provides support Mesophyll – the site of photosynthesis, largely comprised of parenchyma tissue Phloem and Xylem – form veins and conduct food and water,Major Tissues of Leaves,Epidermis,Outer cell layer that covers upper and lower surfaces of leaves,Functions of the Epidermis,Bundle sheath extensions connect the upper and lower epidermis, translucent to allow light to pass through to underlying tissues Also contribute to mechanical support,Functions of the Epidermis,Provides support for the leaf – cells are tough and compact Designed to prevent water loss – cells secrete a waxy waterproof cuticle that is thicker on the upper surface of the leaves and on leaves growing in arid climates Very thin in hydrophytes, very thick in xerophytes,Leaves of a Xerophyte,More Trichomes,Verbascum,Bulliform Cells,Stomata,Pores in the epidermis responsible for the exchange of oxygen, carbon dioxide and water vapor between the leaf and the outside environment Guard cells containing chloroplasts surround the pore If guard cells are full of water (turgid), cells bend and pore opens Occur mostly on the lower epidermis,Mesophyll,Where photosynthesis oc
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