Phloem is a living tissue in vascular plants which conducts the soluble organic compounds synthesized during photosynthesis downwards from the leaves.
The constituents of phloem are:
• Companion cells – it appears to check the activity of the adjacent sieve element and participates in loading and unloading of the sugar into the sieve element
• Sieve tubes – these elongated living cells, conveys carbohydrates, chiefly sucrose from leaves to roots and fruits
• Phloem fibres – they are commercially useful as they possess great pliability and tensile strength
• Phloem parenchyma – also known as transfer cells, they are found near the finest branches, ends of sieve tubes in leaf veinlets, functional here in conveying food