Question

Describe the structure and function of the xylem.

Answer 1

Xylem is the complex plant tissue composed of living and non-living cells. Water and minerals from the soil enter the root epidermis further into the root cell cortex and are passed forward into the xylem. Dissolved minerals and water moves via xylem sap to aerial parts of plants.

Complete answer:
Xylem is made up of tracheids, vessel, xylem parenchyma and xylem sclerenchyma. Tracheids and vessels collectively called the tracheary elements. These are conducting cells of xylem. The vessels are found only in angiosperms and advanced gymnosperms. Tracheids, vessels are thick and are lignified and are dead. The function of xylem parenchyma is the storage of food and xylem sclerenchyma is meant for mechanical support. Tracheids are elongated, spindle-shaped cells with a highly lignified cell wall. The presence of small openings called pits. Vessels are shorter and wider than tracheids. Vessels have perforated end walls that provide a low resistant and efficient pathway for water and mineral transport.

Note: Pits are the microscopic region of tracheids where the secondary cell wall is absent and the primary wall is thin. The upward movement of water and minerals via Xylem against gravitational force is called the ascent of sap. Cohesion, Adhesion, surface tension among water molecules, and transpiration pull to play a key role in the upliftment of water i.e in the Ascent of sap. These properties together provide tensile strength to water and provide a high ability to rise column i.e. capillarity. Xylem is for water transport while Phloem is for food transport from leaves to root.