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Plant Transport Three principle organs of seed plants are roots, stems, and leaves Roots absorb water and dissolved nutrients Anchor plants into ground Hold soil in place & prevent erosion Transport water and nutrients to rest of plant Stems Support system for plant body Transport system that carries nutrients Defends and protects plants Leaves Main photosynthetic systems Broad, flat surface helps increase amount of sunlight absorbed Must contain subsystems to protect against water loss Plant tissue systems Plants consist of 3 main tissue systems Dermal tissue (outside of plant, “skin”) Vascular tissue (“bloodstream”) Ground tissue (everything else) Dermal tissue Outer covering of plant Epidermal cells Covered with thick, waxy layer that protects against water loss and injury Guard cells located on the underside of leaves Regulates water loss and gas exchange Surround Stomata- porelike openings in the underside of the leaf that allow carbon dioxide and oxygen to diffuse into and out of the cell Stomata open and close in response to changes in water pressure within the guard cells Guard cells respond to changes in the environment helping the plant to maintain homeostasis Regulate stomata to balance water loss with rates of photosynthesis Vascular Tissue Forms a transport system that moves water and nutrients throughout the plant Xylem and Phloem Both made of networks of hollow connected cells that carry fluids throughout the plant Xylem Carries water upward from the root to every part of the plant Tracheids- key cells in xylem Hollow cells with thick cell walls that resist pressure Connected end to end like a series of drinking straws Vessel Elements- stacked in columns Phloem Transports solutions of nutrients and carbohydrates produced by photosynthesis from the site of sugar production (source) to the site where sugar is used (sink). Sieve tube elements- main cells in phloem Both forms of vascular tissue can move fluids through the plant body, even against the flow of gravity. Sap- the fluid that moves through the xylem and the phloem Ground tissue The cells that lie between dermal and vascular tissue Mesophyll tissue the site of most of the plants photosynthesis Transpiration- the loss of water through the leaves of plants Transpiration increases when stomata are open Decrease when stomata close Replaced by water drawn into the leaf through xylem vessels in the vascular tissu http://content.bfwpub.com/webroot_pubcontent/Content/BCS_3/Sadava_9e/Animated% 20Tutorials/life9e_3501_xylem_trans.htmle The combination of root pressure, capillary action, and transpiration provides enough force to move water through the xylem tissue of plants Capillary action- the tendency of water to rise in a thin tube Cohesion- attraction of water molecules to each other Adhesion- attraction of water molecules to other substances Water molecules are attracted to each other and to the walls of a tube, causing water to rise Osmotic pressure keeps a plant’s leaves and stems rigid High transpiration rates can lead to wilting- without the pressure inside plant cells, the cell walls bend inward and the plant wilts Stomata then close, which helps the plants to conserve water
