Question

How sieve tubes manage to be living?

Answer 1

Sieve tubes:

1. They are tubular structures with thick cell walls and are found in the complex tissue phloem along with companion cells, phloem parenchyma, and phloem fibres.
2. They do not contain nuclei but cytoplasm so they are dependent upon their adjacent companion cells for certain functions.
3. The companion cells provide ATP, proteins, and other signaling molecules to sieve tube elements.
4. In this way, the sieve tubes manage to live.