Question

Opening and closing of pores is a function performed by 

(A) Stomata 

(B) Chlorophyll 

(C) Chloroplast 

(D) Guard Cells

Answer 1

Hint: Guard cells are the epidermal cells which enclose these pores and those pores are known as stomata. Guard cell contains chloroplast and green colour pigment chlorophyll is present in the chloroplast which helps in photosynthesis.

Complete answer:

• The pores are present on the green surface of the plant which can be on the upper surface of the leaf, lower surface of the leaf, the stem and its branches and all the sepals and bracts of the flower.

• These pores are known as stomata and their main function is exchange of gases like Oxygen and carbon dioxide which is required for the respiration and the photosynthesis of the plant during the day and night. Another function of the stomata is transpiration which is the loss of water from the plant which helps in the transportation of water from Roots to various parts of the plant. This is achieved when water is lost from stomata through the evaporation.

• These functions are mediated by opening and closing of the stomata which is done by modified epidermal cells known as Guard cells.

• Guard cells are Bean shaped cells which have thick walls towards the stomata and thin walls towards its periphery.

• Though the main function of guard cells is to regulate the opening and closing of the stomata they also perform the process of photosynthesis which is possible due to the chloroplast and chlorophyll present in them.

Thus, the answer is Option D: Guard Cell.

Note: It is important to note that stomata are not equally distributed on the surface of the plant, they are found more in number on the lower surface of the leaf as compared to the upper surface. Also, aquatic plants do not have stomata and plants like Water Lily have no stomata on the lower surface of the leaf.