Bulliform

Bulliform refers to a type of cell found in the leaves of many grasses and sedges. These cells are large, empty, and bubble-shaped, hence their name, which comes from the Latin word "bulla" meaning bubble. They are typically located in the upper epidermis of the leaf, often arranged in rows between the vascular bundles.

The primary function of bulliform cells is to regulate leaf rolling and unrolling in response to changes in water availability. When a grass plant is well-watered, the bulliform cells are turgid, meaning they are filled with water and are plump. This turgor pressure causes them to expand, making the leaf surface larger and flatter. This allows for maximum surface area for photosynthesis.

Conversely, when the plant experiences drought or water stress, the bulliform cells lose turgor. As they deflate, they shrink. This shrinkage causes the adjacent, less specialized epidermal cells to fold inwards, resulting in the rolling of the leaf. Leaf rolling is a crucial adaptation for drought survival as it reduces the exposed surface area of the leaf, thereby minimizing water loss through transpiration. This mechanism helps the plant conserve water until favorable conditions return. The presence and arrangement of bulliform cells can vary among different grass species, contributing to diverse leaf morphologies and drought tolerance strategies.