AP BIOLOGY

Detailed explanation-1: -Companion cells are closely associated with sieve elements. Companion cells are associated with sieve elements through plasmodesmata and they together help in the transport mechanism in plants.

Detailed explanation-2: -Companion cells work with sieve tubes or sieve systems and also structurally both present in the surroundings of each other. So, we can say companion cells are most closely related to sieve tissues.

Detailed explanation-3: -Phloem is a complex tissue which is concerned with the transport of food materials from leaves to other plant parts. Phloem is composed of sieve tube elements, companion cells, phloem parenchyma and phloem fibres. sieve tubes are longitudinally arranged cells. It is seen associated with the companion cells.

Detailed explanation-4: -Note: Companion cells are present in the phloem tissue of the flowering plant. This tissue is a special type of parenchyma cells. These cells are closely associated with the sieve tubes. They are connected via cytoplasm of companion cells and plasmodesmata.