Question

Glycolate induced opening of stomata, takes place due to
(a)Presence of oxygen
(b)Low ${C}{O}_{2}$concentration
(c)High ${C}{O}_{2}$ concentration
(d)Absence of ${C}{O}_{2}$

Answer 1

Production of glycolic acid in the guard cells is an important factor in stomatal opening. A glycolate is a metabolite of glycolic acid. Stomata are sensitive towards the internal ${C}{O}_{2}$ concentration in the leaves.

Complete answer:
In 1963, the scientist Zelitch proposed a Glycolate theory, which is responsible for stomatal opening. He suggested that in ${C}_{2}$ plants, photorespiration occurs under low ${C}{O}_{2}$ concentration, and ${O}_{2}$ fixation is done with the enzyme RuBisco, and in this cycle production of glycolic acid take place and dissociation of this acid we get glycolate. He suggested that glycolate is responsible for the production of carbohydrates. In guard due to the production of ${C}{O}_{2}$, the water potential of the guard cell decreases. When water potential decreases, the water from adjacent cells comes into the guard cell, and due to this, the guard cell becomes fully turgid. When there is an increase in turgidity the wall will stretch and due to this the stomatal aperture opens and by this the stomata open and gaseous exchange takes place.
There will a time came in when the ${C}{O}_{2}$ concentration does not decrease, when there is an increase in the concentration of ${C}{O}_{2}$, photorespiration does not take place, due to this the stomata will close. This process is only responsible for the opening of stomata.
So, the correct answer is ‘Low ${C}{O}_{2}$ concentration’.

Note: The guard cells recognize and operate stimuli given environmental and endogenous leading to stomatal opening or closure. The stimuli can be light, humidity, ${C}{O}_{2}$ concentration, temperature, drought, and plant hormones to trigger cellular responses. For instance- Stomata opens at a low concentration of ${C}{O}_{2}$ while closed at a high concentration of ${C}{O}_{2}$.