Chapter 5, Problem 1ACQ

Figure 5.7 On a hot, dry day, plants close their stomata to conserve Water. What impact will this have on photosynthesis?

Summary Introduction

To write:

Description of the impact of the closing of stomata on photosynthesis during hot dry condition.

Introduction:

Stomata are the small opening that exists in the membranes of the plants through which exchange of gas and water takes place. Stomata play an important role in the intake and transpiration of the CO₂ which is significant for the process of photosynthesis.

Explanation of Solution

During hot dry conditions, the stomata close its opening to conserve water. The humidity around the leaves is affected by the temperature of the air around it. If the temperature of the air is higher, the water from the leaves will diffuse more into the air. But it is noted that the leaf has a waxy cuticle blocking the water loss whereas carbon dioxide and oxygen exchange with the environment is required for photosynthesis.

There are specialized epidermal cells around the stomata known as guard cells. These guard cells swell up when there is enough water in the cells opening the stomata. But in case the water is less, these guard cells don't swell and hence the stomata remain closed so that the plant does not lose water. If the stomata are closed, then there is no photosynthesis and the plant will starve.

Conclusion

During the hot dry season, as there is not enough water in the cells, the guard cells do not swell keeping the stomata closed. As result, photosynthesis does not take place and eventually cause starvation of the plant.