Question:

According to starch-sugar conversion theory of stomatal movement, during stomatal opening

Updated On: Jul 27, 2022

$pH$ is lowered and sugar is converted to starch
$pH$ is increased and sugar is converted to starch
$pH$ is lowered and starch is converted to sugar
$pH$ is increased and starch is converted to sugar

Hide Solution

Verified By Collegedunia

The Correct Option is D

Solution and Explanation

According to Llyod $(1908)$, the conversion of starch into sugar in the day time and vice versa at night causes opening and closing of stomata. Sayre $(1926)$, Scarth $(1932)$ suggested that this conversion is controlled only by $pH$ of the guard cells whereas Steward (1964), regards that this is partly enzymatic and partly controlled by $pH$. The change in the $pH$ of the guard cell's cell sap is due to the presence or absence of $CO_2$ which is dependent on light availability. During day time, in the presence of light, $CO_2$ evolved in respiration is utilized for photosynthesis and hence does not accumulate in the guard cells and $pH$ of the guard cells increases to $7$. Hence the enzyme favours the formation of glucose-$1$-phosphate from starch and inorganic phosphate. Altered sugar concentration increases turgidity of the guard cell due to osmosis and stomata open.

Was this answer helpful?

Notes on Transpiration

Concepts Used:

Transpiration

The process by which the plant body releases water in the form of vapors through its aerial portions is known as transpiration. The evaporation of water from the plant portion is also known as transpiration. It is a crucial function in plants that aids other processes and maintains water and nutrient balance. It provides a number of benefits for the plant's body.

Types of Transpiration:

There are three different types of transpiration in plants:

Stomatal Transpiration: It is the evaporation of water from a plant's stomata. The majority of the water from the plants is lost through transpiration. When the stomata open, the water at the surface of the leaves turns into vapor and evaporates.
Lenticular Transpiration: Lenticels are tiny openings in the bark of branches and twigs that allow light to pass through. Lenticular transpiration is the process of water evaporating from a plant's lenticels. Lenticels aren't found in every plant. Through lenticels, only a small amount of water is lost.
Cuticular Transpiration: It is the evaporation of water from a plant's cuticle. The cuticle is a waxy layer that covers the surface of the plant's leaves. Cuticular transpiration loses about 5-10 percent of the water from the leaves. More water is transpired via the cuticles during dry conditions when the stomata are closed.