Phloem sap moves from source to sink under pressure. 1. Aphids, an insect that annoys gardeners, have helped demonstrate that

Question

Phloem sap moves from source to sink under pressure.
1. Aphids, an insect that annoys gardeners, have helped demonstrate that organic
compounds flow under pressure in the phloem. Analysis of the fluid emerging from aphid
stylets (liquid aphids were consuming) verified that in most plant species, sucrose is the
main carbohydrate being translocated through the phloem. The contents of sieve tubes
were found to be under high pressure, often five times as much as in an automobile tire
In flowering plants, sucrose-laden phloem sap flows from a starting location, called the
to another site, called the
along gradients of
decreasing solute concentration and pressure. The pressure flow mechanism builds up at
the source end of a sieve tube system and pushes those solutes by bulk flow toward a
sink, where they are removed

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