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Phloem carries food from a source to a sink, and the direction of this flow can be either upward or downward. This movement in the phloem is therefore described as what?
AStrictly upward only
BBidirectional
CStrictly downward only
DCompletely stationary
Answer & Solution
Correct answer: B. Bidirectional
1. The source makes food and the sink uses or stores it.
2. Because the source and sink can switch with season or need, flow can reverse.
3. Xylem flow is always upward, but phloem is not limited that way, ruling out options A and C.
4. Phloem flow that can go either way is bidirectional, option B.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 14 Transportation in Plants and Circulation in Animals "Phloem Transport", p.210_
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