What can cause an increase in the rate of transpiration?
a. increase in temperature
b. increase in air movement
c. increase in soil moisture
d. all of the above

The answer is d. all of the above.

Transpiration is a water loss from a plant in the form of water vapor through small pores on the leaves.

The increase in temperature will increase the transpiration rate. When the temperature is increased, the air is warmer and dryer. There is more water in the leaves than in the air, so the more water will be released from the plant.

The increase in air movement will increase the transpiration rate. If air movement is increased, it will faster move the saturated air from the leaves, leaving dryer air close to the leaves. Similarly to the temperature effect, more water will transpire from the leaves.

The increase in soil moisture will increase the transpiration rate. When an increase in soil moisture is present, a plant will take more and more water will be transpired.