Describe components of phloem. Define translocation.

Phloem is made up of four types of elements: Sieve tubes, companion cells, phloem fibres and the phloem parenchyma.

(i) Sieve tubes: These are tubular cells with perforated walls. These cells are responsible for transportation of food and nutrients.

(ii) Companion cells: These cells are found associated with sieve tubes and connected with it by simple pits. These cells are long, narrow and thin walled. These cells are living.

(iii) Phloem fibres: They have thick cell wall and they provide mechanical support to plant.

(iv) Pholem parenchyma: These cells are living and often cylindrical in shape.

The transport of food from leaves to other parts of the plant is called translocation