Question

are sieve tube elements living or nonliving?give reasons.

Answer 1

Sieve tube elements are living components 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.