Phloem and its functions

Phloem:

Phloem (bast) is a living conducting tissue. It also contains tubes just like xylem but does not perform mechanical function.

Phloem is composed of following four elements or cells:

(i) Sieve tubes 

(ii) Companion cells  

(iii) Phloem parenchyma  

(iv) Phloem fibers.

Sieve tubes are slender, tube like structures with perforated walls.

Companion cells are living parenchymarous cells lying on the sides of the sieve tubes.

Sieve tube and companion cells have close cytoplasmic connection with each other through fine pits.

Phloem fibres are thick walled fibres with simple pits.

Phloem parenchymas are thin walled, living cell of parenchyma of phloem.

Function:

Phloem transports (conducts) photosynthetically prepared food materials from the leaves to the storage organs and later from storage organs to the growing regions of the plant body.