List four component elements of phloem. Which one of them is most important and why?
Phloem consists of the following four elements:
(i) Sieve tubes (ii) Companion cells
(iii) Phloem parenchyma (iv) Phloem sclerenchyma.
The most important element of phloem is sieve-tubes because they translocate food materials from leaves to other parts of plant.