plant transport

plant transport - CHAPTER 36 +Lithops (Stone Plant)...

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Plant transport systems To grow and reproduce, plants need resources: O 2 , for respiration water if photosynthetic, CO 2 and access to light in addition to the C, H, and O in water and CO 2 , 14 essential elements if not photosynthetic (i.e., if heterotrophic), a source of reduced carbon compounds Plant transport systems Photosynthetic land plants face major transport problems that get worse as size increases: 1. All of the nutrients needed for photosynthesis -- except CO 2 -- come from the soil (root system) ….. but photosynthesis occurs far away in the leaves (shoot system) 2. Photosynthesis takes place in leaves , but photosynthetic products (sugars) are need in all parts of the plant Bulk flow of materials is essential! (cell-to-cell processes too slow for 2 and 3) Plant transport systems Therefore, plants need to move large quantities of substances over long distances : 1. from soil into roots (water and nutrients) 2. from roots to leaves (water and nutrients) 3. translocation of photosynthetic products By several means, soil nutrients are moved into root tissue: diffusion (if concentration in soil is higher than in roots) -- may be facilitated by transport proteins cation exchange -- addition of H + to soil to displace positively charged minerals (cations) from negatively charged soil particles (secretion of H + ; release of CO 2 ) active transport against a concentration gradient Requires expenditure of ATP proton pump generates transmembrane proton gradient (= a form of energy storage) electrical gradient (negative inside of cells) drives uptake of cations (i.e., K + ) cotransport of substance with protons (i.e., NO 3 - absorbed along with H + ) H + H + H + H + H + H + H + H + H + H + - - - - - - - K + NO 3 -
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Root cross-section Root hairs Vascular cells (stele) Once inside the root, how do nutrients reach the vascular system? At least initially, two possible pathways: via the Apoplast (non-living tissue; i.e., cell walls) Root cross-section Once inside the root, how do nutrients reach the vascular system? At least initially, two
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This note was uploaded on 07/31/2008 for the course BIO 5B taught by Professor Chappell during the Spring '07 term at UC Riverside.

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plant transport - CHAPTER 36 +Lithops (Stone Plant)...

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