Question

Steward's theory of stomatal opening and closure assumes the pressure in the guard cells, of the following enzymes

• A. Phosphorylase and Phosphatase
• B. Hexokinase and Phosphoglucomutase
• C. Phosphorylase, Phosphoglucomutase, Phosphatase and Hexokinase
• D. Phosphorylase and Phosphoglucomutase

Answer 1

The correct option is C Phosphorylase, Phosphoglucomutase, Phosphatase and Hexokinase

According to Steward theory, starch phosphorylase derives glucose-1-phosphate from starch, phosphoglucomutase converts glucose-1-phosphate into glucose-6-phosphate. Phosphatase converts glucose-6-phosphate into glucose and stomata opens due to the accumulation of glucose in guard cells.
During dark these changes are reversed; hexokinase converts glucose into glucose-6-phosphate which is converted back to starch by the action of phosphoglucomutase and starch phosphorylase. As starch is osmotically inactive the stomata close down.