What are bulliform cells? What are their functions?

Bulliform cells, also known as motor cells or motor parenchyma cells, are specialized plant cells found in the leaves of many grasses and certain monocotyledonous plants. These cells are responsible for the phenomenon known as leaf rolling or leaf folding, which is an adaptive response to changes in environmental conditions, particularly water availability.

The primary function of bulliform cells is to regulate the rolling and folding of leaves, which helps plants conserve water and reduce water loss through transpiration. Transpiration is the process by which plants release water vapor from their leaves into the atmosphere. By controlling leaf orientation and surface area exposed to the environment, bulliform cells can help plants adapt to varying moisture levels.

When the plant is well-hydrated, bulliform cells are turgid, meaning they are filled with water and are in an expanded state. This turgidity causes the leaves to be flat and fully exposed to light, which is essential for photosynthesis. However, when the plant experiences water stress, such as drought or water scarcity, bulliform cells lose water and become flaccid. This loss of turgor pressure causes the leaves to curl or roll inward, reducing the surface area exposed to the air and sunlight. This rolling action minimizes the exposure of leaf surfaces to the atmosphere, thereby reducing water loss through transpiration and helping the plant conserve water.

In summary, bulliform cells play a crucial role in the adaptation of certain plants to changing water availability by controlling leaf rolling and folding. This adaptation allows plants to optimize their water-use efficiency and survive in environments with fluctuating moisture levels.