Question

1. It’s 100 degrees and not a cloud is in sight. What do you expect to happen to the rate of water movement through the plant? Explain why.

A) It will speed up, because the amount of water available to be absorbed by the roots is decreased.

B) It will speed up, because the rate of transpiration will increase.

C) It will stay the same because transpiration rate is naturally regulated.

D) It will slow down, because the cohesion among the water molecules will decrease.

E) It will slow down, because transpiration will decrease due to the lack of a humidity gradient.

Answer 1

Option B is the correct answer.

At 100 degrees atmospheric tempreature with not a cloud in sight, i.e., in low realtive humitive leading to drier conditions, the rate of transpiration will increase because of a steeper water gradient potential. Warmer air has a much higher capapcity of carrying water and drier the atmosphere, the larger the driving force for water movement out of the plant, thus increasing the rate of transpiration. Hence, the rate of water movement throught he plats will speed up due to increased rate of transpiration.