Stomata

Stomata: An Overview

• Stomata are minute openings or pores in plant tissue that allow for gas exchange.
• They are typically found on the undersides of leaves but can also be present on stems.
• Each stoma (singular of stomata) is surrounded by a pair of guard cells which control the opening and closing of the stoma.

Function of Stomata

• Stomata play an essential role in photosynthesis, whereby carbon dioxide (which is needed for photosynthesis) enters the plant, and oxygen (a by-product of photosynthesis) exits.
• They also facilitate the process of transpiration, which is the evaporation of water from plant surfaces, primarily through the stomata.

Control of Stomata Opening and Closing

• The guard cells control the size of the stoma by changing shape in response to environmental conditions.
• When there is ample water, the guard cells fill with water, become turgid, and the stoma opens. This allows for gas exchange needed for photosynthesis and transpiration.
• If water levels are low or the environmental conditions are harsh, the guard cells lose water, become flaccid, and the stoma closes. This reduces water loss through transpiration.

Factors Affecting Stomatal Activity

• Light: Stomata usually open in the presence of light (which is when photosynthesis occurs) and close in the dark.
• Humidity: Stomata tend to close if the external humidity is low, to reduce water loss.
• Carbon dioxide concentration: High levels of carbon dioxide inside the leaf can lead to stomata closure.

Stomata in Food and Ecosystems

• Stomata enable plants to obtain carbon dioxide for photosynthesis, which in turn produces glucose, an essential source of energy for other organisms in the ecosystem.
• By controlling water loss, stomata play a critical role in a plant’s overall water balance and survival.
• The release of oxygen through stomata contributes to the global oxygen cycle, supporting aerobic respiration in animals and other organisms.