Homwork self for exam 2

Homwork self for exam 2 - 1.

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1. Explain step-by-step how the cohesion-tension hypothesis works (all the  way from leaves down into roots. The transpiration-cohesion-tension mechanism can be explained as a series of sequential steps: 1. The first step is the diffusion of water from the leaf through the stomatal pores. This is transpiration, and it provides the force driving the transport of water. 2. As water exits the leaf, more water evaporates from the cell walls of the leaf into the extensive air spaces within the leaf. 3. As water evaporates from the cell walls, this loss pulls more liquid water from the xylem of the leaf. This flow occurs because the water in the tiny pores and crevices in the cell walls is continuous with the water in the xylem vessels and because the continuous water molecules are held together by the high cohesion of water. 4. Cohesion also accounts for the flow of the column of water from the xylem of the root to the xylem of the leaves, as water is lost through the stomata. 5. As water flows upward in the root, water influx from the soil fills the void. 2. Explain step-by-step, how phloem transports sucrose from source to sink,  regardless of the direction of xylem transport.
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This document was uploaded on 08/10/2011.

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Homwork self for exam 2 - 1.

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