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Unformatted text preview: (The cells collapsed and quit functioning when manipulated.) Ultimately, the common aphid was used as a research tool. Aphids normally penetrate into phloem to feed, and their actions do not stop the phloem activity in the plant. Aphids merely divert the flow into (and sometimes through) the aphid body. Sucrose has a high osmotic potential (hydrostatic pressure). While sucrose, like any substance, can move by diffusion, the normal rate of phloem movement is much faster than simple diffusion. Movement in phloem is always in a direction of more concentrated solute to less concentrated, or from where you have solutes (mostly sugars from photosynthesis) to where you need the solutes. Phloem can also be used to move solutes from storage areas to where solutes are needed. This pressure-flow gradient between the source of solutes and the sink, the location to which the solutes are being moved, explains how solutes are moved through phloem....
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This note was uploaded on 01/08/2012 for the course BIO 213 taught by Professor Makina during the Fall '09 term at SUNY Stony Brook.
- Fall '09