20150520 Day 11 Sugar transport II

20150520 Day 11 Sugar transport II

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Pressure Flow Hypothesis: Three phases of sugar transport 1. Phloem loading 2. Bulk flow 3. Phloem unloading
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2. Bulk Flow What determines the rate of sap transport from source to sink?
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Aphids eat phloem sap by sticking their mouthparts (stylus) into sieve cells. If you pull off the aphid body the stylus will stay in the sieve cell. If the pressure flow hypothesis is correct, what will be the relative sizes of phloem droplets on styluses in stem near a photosynthesizing leaf and a stem near to roots. A) Source droplet > Sink droplet B) Source droplet < Sink droplet C) Source droplet = Sink droplet
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1. Phloem loading: generate high P
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