Question

Sunken stomata
A. Increase transpiration
B. Decrease transpiration
C. Hinder transpiration
D. Stop transpiration

Answer 1

Hint: Transpiration is the process in which water is loosed out from the leaves. The loss of water from the leaves takes place from the stomata that are embedded in the surface of the leaves. We all know that as the stomata get sunken, the surface area decreases.

Complete answer:
Transpiration is the evaporative loss of water by plants. This process of loss of water occurs mainly through the stomata that are generally present on the surface of the leaves. Apart from the loss of water vapour in transpiration, the exchange of oxygen and carbon dioxide can also take place through these pores which are called stomata. Normally stomata are open in the daytime and close during the night. The immediate closing and opening of the stomata is the change in the turgidity of the guard cells.

Usually, the lower surface of a dorsoventral leaf has a greater number of stomata whereas in an isobilateral leaf they are about equal on both surfaces. Transpiration is affected by many external factors like temperature, humidity, light and wind speed. There are some plant factors that affect the process of transpiration, which are the number and percent of open stomata, water status of the plant, canopy structure, distribution of stomata and many more.

Sunken stomata are found primarily in xerophytes. Instead of them being on the leaf surface they are majorly sunken into the leaf and usually are surrounded as well as partially covered by cuticles and hairs called trichomes. They are generally found in arid environments so the process of photosynthesis uses and wastes a disproportionate amount of water.

The open sunken stomata present on the surface of the leaf is shielded from the drying winds. The hair-like trichomes maintain a moist atmosphere and they usually slow down the water loss. The gas exchanges that take place through these stomata are usually accomplished with less water loss. These sunken stomata reduce the loss of water through these stomata as they can remain open longer in the daytime, thereby replenishing the $CO_2$ levels inside the leaf that is generally needed for the completion of the photosynthesis processes for a greater part of the sunlit day than those plants that would have to close their stomata.

 Sunken stomata generally have reduced surface area of the pores. Due to which the loss of water is less as compared to one having turgid stomata. In other words, we can say that the transpiration rate decreases with the size of the stomata.

So, the correct answer is option B, which Decreases transpiration.

Note: Water is transient in nature in plants. To your surface, less than 1 percent of the water reaching the leaves is generally used up in the process of photosynthesis and in plant growth. Most of it is mainly lost through the stomata in the leaves. This water loss is known as transpiration.