Guard Cells

Guard cells are specialized cells found in the epidermis of leaves and stems of plants. They are responsible for regulating the opening and closing of the stomata, which are tiny pores on the surface of the leaf or stem that allow for gas exchange.

Structure of Guard Cells

Guard cells are bean-shaped cells that surround the stomatal pore. Each guard cell contains chloroplasts, which are responsible for the production of energy through photosynthesis. The inner side of the guard cells is thicker than the outer side, giving them a kidney or bean-like shape.

Function of Guard Cells

Guard cells control the opening and closing of the stomata through changes in their shape. When the guard cells are turgid (swollen with water), they bow outwards, opening the stomatal pore. This allows for the exchange of gases such as carbon dioxide and oxygen, as well as the release of water vapor through transpiration. When the guard cells lose water and become flaccid, they shrink and close the stomatal pore, reducing water loss and gas exchange.

Regulation of Guard Cells

The opening and closing of stomata by guard cells is regulated by various factors including light, carbon dioxide levels, and internal plant signals. For example, in the presence of light, guard cells take up potassium ions and water, causing them to swell and open the stomatal pore. Conversely, in darkness or during water stress, the loss of potassium ions and water causes the guard cells to become flaccid and close the stomata.

Study Guide

1. Describe the structure of guard cells and their location in plants.
2. Explain the function of guard cells in regulating gas exchange and transpiration.
3. Discuss the role of guard cells in responding to environmental factors and plant signals.
4. Compare and contrast the behavior of guard cells in light and dark conditions.
5. Explain the relationship between guard cells, stomata, and photosynthesis in plants.

Understanding the structure and function of guard cells is important for comprehending plant physiology and the mechanisms that plants use to adapt to their environment.