Question

Sieve tube elements are always associated with companion cells. Suggest three possible reasons.

Answer 1

1) they do not have Nucleus

Answer 2

Reason for association of Sieve tube elements with companion cells:

The sieve tube elements and the companion cells are two types of cells which are present in the phloem sieve tubes. They both are always seen in association with one another.

The following are the reason for association of Sieve tube elements with companion cells:

• The absence of nuclei and presence of only few cell organelles in sieve tubes.
• Due to presence of large numbers of Plasmodesmata between “sieve tube elements and companion cells”.
• The fusion of cytoplasm of both of the cells is essential for “symplastic exchange of metabolites”.