If the humidity of the atmosphere suddenly increases substantially, the water flow in the xylem will
Increase sharply and then reduce slowing to the pre-existing level
The correct option is B Decrease
Transpiration is the loss of water in the form of water vapor from the parts of the plant. This takes place with the help of stomata that are mostly present on the lower surface of leaves. Their opening is controlled by specialized cells called guard cells to regulate the water loss. The water is carried to the stomata through the xylem. A high humidity decreases the rate of evaporation of water due to transpiration. Thus, the correct answer is option B.