Phloem is a conducting tissue concerned with the conduction of food material in plants. It is made of four elements; sieve tube, comparison cell, Phloem Parenchyma and Phloem fibres. Phloem is mainly responsible for the conduction or transport of organic food prepared by plant.
Sieve tube is slender, tubular structures with perforated cross walls in the form of sieve plates. Through these plates, the food material passes from cell to cell. End walls of the cells have holes on them, which give them the name sieve. Cell wall is cellulosic.
Companion cells are long, living and rectangular cells associated with sieve tubes. They control flow of food through the sieve tubes. Cell wall made up of cellulose.
These are living parenchymatous cell concerned with food. Elongated cells and cell wall thin and made of cellulose.
These are sclerenchymatous cells associated with phloem. They are more frequency in secondary phloem and very long cells with thick lignified walls.