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NEST2026BiologyTransport in Plants

The ability of phloem to distribute sugar depends on the companion cell and sieve element working as a complex. Consider the following statements with regard to possible effects of reduction in companion cell plasmodesmata. (i) Sugar loading into sieve tubes reduces due to collapse in osmotic pressure gradient. (ii) Water moves from companion cells into the xylem to maintain osmotic balance. (iii) The sieve tubes col

Options

  1. A(iii) and (iv)
  2. B(i) and (iii)
  3. C(i) and (ii)
  4. D(ii) and (iv)

Correct answer

B. (i) and (iii)

Step-by-step solution

Companion cells and sieve tube elements function together as a complex to load and transport sugars in the phloem. Sugars are loaded from companion cells into sieve tubes through plasmodesmata. If there is a reduction in companion cell plasmodesmata, the transfer of sugars into the sieve tubes is hindered. This leads to a significant decrease in sugar loading, which in turn causes a collapse in the osmotic pressure gradient that normally draws water into the phloem. Due to the reduced solute concentration in the si

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