PLANT PHYSIOLOGY
TRANSPORT IN PLANT
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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An experiment was performed on a young plant using an aphid stylet to measure the rate of transport in the phloem. The same plant was then placed in a bell jar and a chemical placed in the bell jar to absorb all the oxygen present. The rate of transport in the phloem decreased and then stopped. What is the reason for this?
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Companion cells no longer produce sufficient energy.
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Mitochondria in the xylem vessels cease to function.
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Photosynthesis cannot occur in the bell jar.
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Translocation occurs only by diffusion.
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Explanation:
Detailed explanation-1: -The droplet of phloem sap can then be analysed for traces of the isotope to determine transport rate. Aphids can be placed along the length of the plant stem to show transport along various distances.
Detailed explanation-2: -Aphids don’t suck; rather, the phloem contents are forced into the aphid (thus the phloem is under pressure) and the excess oozes out the anus (honeydew). Thus, aphid studies demonstrate that the phloem is under pressure. Further, the honeydew can be collected and we can identify its composition.
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