Relation between sieve tubes and companion cells:

The key element of Phloem is the sieve component and the companion cell. The sieve element is known as the sieve tube in angiosperms, and the cell associated with it is known as a companion cell. The sieve element is a sieve cell in gymnosperms and other primitive vascular plants, while the associated cell is referred to as an albuminous cell.

Relation between sieve tubes and companion cells is that they form a sieve element and companion cell complex.

Similarities between sieve tubes and companion cells

Below are the similarities between the two:
(a) Both are two different types of cells that are found on the phloem of angiosperms.
(b) Transportation of food throughout the plant is done by these two cells.
(c) Both the cells have an elongated shape.
(d) Both the cells emerge from the meristem.