Group7-Xylem vessel

A vessel element is one of the cell types found in xylem, the water conducting tissue of plants. In secondary xylem, a vessel element originates from a fusiform initial in the cambium, at maturity the protoplast dies and disappears, but the lignified cell walls persist.At both ends there are openings that connect the individual vessel elements. These are called perforations or perforation plates. These perforations may have a variety of shapes: the most common are the simple perforation (a simple opening) and the scalariform perforation (several elongated openings on top of each other in a ladder-like design). Other types include the foraminate perforation plate (several round openings) and reticulate perforation plate (net-like pattern, with many openings). The side walls will have pits, and may have spiral thickenings.

The vascular bundle in the stem of plants is composed of the xylem and phloem tubes. The xylem’s main function is to transport water and mineral salts from the roots to the rest of the plant. The xylem is composed of xylem vessels, xylem tracheids, xylem fibres and xylem parenchyma. The xylem vessel is a long, hollow tube stretching fromthe root to the leaf. It is a structure made up of many dead cellsknown as vessel elements. The cells are arranged end to end and thecross-walls dissolve completely or have simple or complex perforationplates between successive cells. The secondary walls of vessels are impregnated with lignin and are thickened unevenly. Lignin may bedeposited in the form of rings or spirals, to prevent the collapse of the vessel and to provide mechanical support to the plan. The xylem vessel also has an empty lumen without protoplasm, to reduce resistance to water flowing through the xylem.