AP BIOLOGY

Detailed explanation-1: -The transverse partition wall between the two cells is perforated with the pores. The sieve tubes are the part of phloem with the perforated walls. Therefore, it appears like a sieve and it is named as a sieve plate. The sieve cells are also associated with gymnosperms because they lack in the companion cell.

Detailed explanation-2: -A set of perforations in the wall area of a sieve tube is called a sieve area.

Detailed explanation-3: -sieve element, in vascular plants, elongated living cells of the phloem, the nuclei of which have fragmented and disappeared and the transverse end walls of which are pierced by sievelike groups of pores (sieve plates). They are the conduits of food (mostly sugar) transport from the leaves to the rest of the plant.

Detailed explanation-4: -The sieve tubes consist of thick primary walls with perforated end walls, transverse or oblique. The transverse end wall of the sieve tube is called the sieve plate, which is perforated by groups of pores.

Detailed explanation-5: -Phloem tissue consists of two types of cells, sieve tubes and companion cells and both have perforated cell walls. Tracheids cells do not have perforated cell walls.