Question

Who proposed that opening and closing of stomata is connected with the change in pH of guard cells?
A. Lloyd
B. Von Mohl
C. Sayre
D. Levitt

Answer 1

Hint: Guard cells are special kinds of plant cells that control gas exchange present in epidermis of leaves, stems and other organs. The stomatal pores are largest at that time when water is available freely and guard cells are turgid. When the water is not available much the guard cells become flaccid and stomatal pores closed.

Complete answer:
Photosynthesis depends on the diffusion of carbon dioxide gas through the stomata in the mesophyll tissues from the air. Byproduct of photosynthesis is that oxygen exits the plant via the stomata. When in the daytime the carbon dioxide is being used constantly there is a state of neutral and alkaline pH and in night time when there is no process of photosynthesis an acidic medium is formed due to accumulation of carbon dioxide that forms carbonic acid.

> Option A - Lloyd: D.G. Lloyd’s major contribution to botany was in the field of plant reproduction not linked at all with opening and closing of stomata so we will not consider this option as our answer.

> Option B - Von Mohl: He is a german botanist, he is one of the botanists who is the founder of plant cytology. He gave a classification of plant tissue and also proved the cellular origin of the vessels of the conducting system and also gave observative study about the formation of starch in chloroplasts.

> Option C - Sayre: Botanist Sayre observed that stomata opening is connected to change in pH of guard cells due to carbon dioxide gas. This is our right answer.

> Option D - Levitt: Levitt was one of the researchers that conducted molecular dynamics simulations of DNA and proteins and developed a software for this process.

Hence, the correct answer is option (C).

Note: Stomata opens in neutral and alkaline pH this state is present in daytime when exchange of gases is taking place continuously and carbon dioxide is used constantly. When there is no process of photosynthesis taking place as that in night time accumulation of carbon dioxide causes the formation of carbonic acid and an acidic medium is generated. The movement of guard cells is guided or regulated by pH due to interconversion of sugar and starch. This is how our answer is justified.