HORTICULTURE

HORTICULTURE SCIENCE

PLANT BIOLOGY

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What causes the water in xylem vessels to be under tension?
A
gravity
B
cohesion
C
adhesion
D
evaporation
Explanation: 

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: -According to the cohesion-tension theory, the water in the xylem is under tension due to transpiration.

Detailed explanation-3: -Transpiration is the loss of water from the plant through evaporation at the leaf surface. It is the main driver of water movement in the xylem. Transpiration is caused by the evaporation of water at the leaf–atmosphere interface; it creates negative pressure (tension) equivalent to –2 MPa at the leaf surface.

Detailed explanation-4: -What happens to the tension in the xylem when the stomata close and evaporation stops? It goes to zero once evaporation ceases.

Detailed explanation-5: -The bulk of water absorbed and transported through plants is moved by negative pressure generated by the evaporation of water from the leaves (i.e., transpiration)-this process is commonly referred to as the Cohesion-Tension (C-T) mechanism.

There is 1 question to complete.