Question

Gymnosperm lack companion cells. Then how sieve tubes are controlled?

Answer 1

Nuclei of companion cells control the metabolic activities of sieve tube elements as they are devoid ofnucleus. Its function is uncertain, though it appears to regulate the activity of the adjacent sieve element and to take part in loading and unloading sugar into the sieveelement . They enable the sieve cells to be connected to parenchyma, functional tissue in the organs, which helps to stabilize the tissue and transport nutrients. Sieve cells are also associated with gymnosperms because they lack the companion cell and sieve member complexes

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