EVERYDAY SCIENCE

Detailed explanation-1: -The nucleus of companion cells controls the metabolic activity of the sieve tubes.

Detailed explanation-2: -Sieve cells are long, conducting cells in gymnosperm phloem. Albuminous cells have long, unspecialized areas with overlapping ends with the ends of other sieve cells and contain stored food and nutrients in order to nourish the tissues.

Detailed explanation-3: -Both albuminous cells and companion cells function to load and unload sugars into the cavity of the sieve cells or sieve tube members. Sieve cells (and associated albuminous cells) are the ancestral sugar-conducting cells and are found in all nonflowering vascular plants.

Detailed explanation-4: -Albuminous cells are also called as Strasburger cells. They lack starch, thus making it possible to differentiate them from phloem parenchyma.