Question

Explain all the elements of xylem and phloem.

Answer 1

Vascular tiisue system of the plant helps in the transportation of water and food in the plant.
Xylem – This tissue helps in the transport of water and dissolved substances throughout the plant. The different components of the xylem include tracheids, vessels, xylem parenchyma and xylem fibres.
*Tracheids form the main conductive cells of some non-flowering plants. Water moves from the cell to cell through side walls. These cells aer elongated cells with tapering ends. These cells with cell walls bear spiral, pitted or bordered-pitted thickenings.
*Vessels are advanced water conductive elements mostly seen in flowering plants. The cell walls are thickened with lignin. These provide rigidity and resistance to the cell walland prevents it from collapsing during excess transpiration.
*Xylem parenchyma are the living cells of the xylem. They perform functions like secretion and storage.
*Xylem fibres are midway between tracheids and xylem parenchyma (libriform fibres). They provide lot of support to the plants.


Phloem is composed of several cell types including sclerenchyma, parenchyma, sieve elements and companion cells. The sieve element and companion cell are found closely associated with each other in what is referred to as the sieve element/companion cell complex. One or more companion cells may be associated with a single sieve element.

The so called “sieve element” may be more specifically referred to as a sieve tube member (angiosperms) or sieve cell (gymnosperms and ferns). The sieve cells of gymnosperms lack a sieve plate and instead have sieve pores throughout the cell wall which allow flow between adjacent cells. The sieve tube members found in flowering plants are generally wider than sieve cells and have sieve plates connecting the ends of adjacent cells. These sieve plates are areas with many pores through which adjacent cells are connected by a continuous cytoplasm.