EVERYDAY SCIENCE

Detailed explanation-1: -Sieve tubes are considered living cells without a nucleus because the nucleus of companion cells controls their functional activities. Companion cells, which unite with sieve tubes to form the sieve element-companion cell complex, are related to sieve-tube members.

Detailed explanation-2: -Red blood cells from mammals and vascular plant’s sieve tube cells have nuclei in their early stages, but they lose them as they mature. As a result of their adaptation, these cells no longer have nuclei, are unable to divide, and have a short lifespan.

Detailed explanation-3: -Sieve tube elements, also known as sieve tube members in plant anatomy, are highly specialised types of elongated cells found in flowering plants’ phloem tissue. Sieve elements are living cells, as opposed to water-conducting xylem vessel elements, which are dead when mature.

Detailed explanation-4: -Sieve tube elements do not have nuclei but have cytoplasm. They are dependent on adjacent companion cells which contains dense and very active cytoplasm and a large elongated nucleus.

Detailed explanation-5: -Complete answer: the nucleus is absent in mature sieve tube cells and mammalian erythrocytes. Sieve tube is described as the cells of the phloem tissue present in vascular plants.