Question

Identify and define ‘A’ and ‘B’ in relation to the uptake of water by the root: 

Hint:

Root hairs are short-lived but crucial for efficient water absorption. The Casparian strip in the endodermis ensures that water passes through a regulated symplastic route before reaching the xylem.

Answer 1

A - Root Hair: Specialized epidermal cells that increase the surface area for water absorption. 
B - Xylem: Vascular tissue responsible for the conduction of water and minerals from roots to other parts of the plant. 
In plants, the root system is responsible for the uptake of water and minerals from the soil. The given diagram shows a longitudinal section of the root, highlighting structures involved in this process. 
1. Identification of 'A' - Root Hair: Root hairs are elongated extensions of epidermal cells that increase the surface area for absorption. They facilitate osmosis, allowing water to move into the root cells due to the concentration gradient. 
2. Identification of 'B' - Xylem: Xylem consists of tracheids and vessels that conduct water and dissolved minerals from the roots to the rest of the plant. It plays a key role in the ascent of sap, moving water upwards due to transpiration pull, cohesion, and adhesion forces. 
Mechanism of Water Uptake: 
(i) Water moves from the soil into the root hairs through osmosis. 
(ii) It travels across root cortex cells by the apoplast pathway (through cell walls) or symplast pathway (through plasmodesmata). 
(iii) Finally, water enters the xylem and is transported upwards by transpiration pull.