Question

Although sieve tube are without nucleus.how they manage to be living??

Answer 1

Sieve tube elements are living compounds of phloem.

They contain the living protoplasm i.e cytoplasm that provides raw material and enzymes for various metabolic activities of the cell rendering it living.

Though, it does not contain nucleus yet, it is living because all the controlling activities of nucleus are taken over by the nucleus of the adjacent companion cells.

Any cell devoid of nucleus that contains cytoplasm is considered living.