NEET BIOLOGY

Detailed explanation-1: -The tension created by transpiration “pulls” water in the plant xylem, drawing the water upward in much the same way that you draw water upward when you suck on a straw. Cohesion (water sticking to each other) causes more water molecules to fill the gap in the xylem as the top-most water is pulled toward the stomata.

Detailed explanation-2: -The movement of water in the xylem is unidirectional and is always upward. The upward movement of water is due to pressure created by transpiration, i.e. transpiration pull.

Detailed explanation-3: -The suction force (negative pressure) created by transpiration from the leaves’ surface draws water from the soil and roots through the xylem. Water is sucked up as a result of the xylem vessel. Due to the appearance of capillary action, transpirational pull moves water from roots to leaves.

Detailed explanation-4: -The upward movement of water from roots towards the tips of stem branches and their leaves is called the ascent of sap. It occurs through the tracheary elements of the xylem.

Detailed explanation-5: -According to the cohesion-tension theory, transpiration is the main driver of water movement in the xylem. It creates negative pressure (tension) equivalent to –2 MPa at the leaf surface. Water from the roots is ultimately pulled up by this tension.