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Jan. 24th-Test 1 - plasmodesmata to the xylem B.4 B.5...

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I. Plant H 2 O Movement and Water Deficit A. Movement from the soil into the root xylem and toward the leaf A.1. As water in the Xylem moves toward the mesophyll cells, a tension develops in the water column and Psi of the xylem decreases below that of the outer Parenchyma cells of the root. A.2. Water moves from the outer parenchyma cells of the root to the xylem, so Psi of the root is less than Psi of the soil. A.3. Therefore, evaporation of water from the mesophyll cells and its escape via the stomata during the day is the main reason for the development of a low Psi in the plant Water only moves into the plant when Psi of the plant is less than the Psi of the soil. B. Root H 2 O Movement B.1. Root Anatomy- young roots of a true are the only roots absorbing water and nutrients B.2. The presence of the endodermis forces water to move into living cells of the epidermis and cortex parenchyma B.3. Then movement from parenchyma cell to parenchyma cell via
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Unformatted text preview: plasmodesmata to the xylem B.4. B.5. Plasmodesmata are strands of protoplasm connecting parenchyma cells. C. Water Deficit Stress C.1. Why study water movement and water-deficit responses? • Most plant productivity is water-limited • Water availability may decrease in may agricultural areas in the future • The human population is still growing C.2. Stages of Water Deficit • Mild Stress- No wilting, frequent in afternoons C.2. .a. Problems → very low growth • Moderate Stress- some afternoon wilting C.2. .a. Problems → reduction in photosynthesis by 50%, no growth in the afternoon, but still at night • Severe stress- wilting most of the day C.2. .a. Problems → no growth and low photosynthesis occurrences C.2. .b. Membrane damage in Parenchyma cells and protein denaturation are two things that will kill the...
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