Mechanism of Opening and Closing of the Stomata

Structure of the Stomata

The basic structure of a stomata includes an opening surrounded by two specialized cells called guard cells. These guard cells control the opening and closing of the stomata to regulate gas exchange and water loss in plants. The shape of the guard cells and the degree of their opening are influenced by various environmental factors such as light, humidity, and carbon dioxide levels. This structural arrangement enables efficient gas exchange while minimizing water loss through transpiration.

Opening and Closing of the Stomata

- During the day chloroplast of guard cells accumulate sugar / glucose produced through the process of photosynthesis;
- Accumulated sugar / glucose in the guard cells increases osmotic pressure of the cell sap of the guard cells;
- Water is drawn from the neighbouring epidermal cells by osmosis;
- Guard cells become turgid and bulges outward;
- This opens the stomata;
- At night, sugar / glucose which had accumulated in guard cells is converted to starch;
- Osmotic pressure of guard cells falls;
- The cells lose water to the neighbouring epidermal cells and become flaccid;
- The guard cells are drawn towards one another
- The stomata closes;