spongyparenkym

Spongy parenchyma, also known as spongy mesophyll, is a type of plant tissue that forms part of the leaf mesophyll. It consists of loosely arranged parenchyma cells with numerous intercellular air spaces, giving the tissue a sponge-like appearance.

Location and structure: In most leaves, spongy parenchyma lies below the palisade mesophyll and above the lower epidermis. The cells are generally more irregular in shape and less densely packed than those of the palisade layer, and they contain chloroplasts to varying degrees. The large air spaces between cells connect with stomatal chambers, forming a network that facilitates gas movement.

Function: The primary role of spongy parenchyma is to aid gas exchange within the leaf. The intercellular air spaces allow diffusion of carbon dioxide toward photosynthetic cells and promote the outward movement of oxygen and water vapor. While photosynthesis occurs throughout the mesophyll, the spongy layer contributes to efficient gas diffusion and helps regulate internal leaf humidity and temperature.

Variation and significance: The extent of spongy parenchyma and the size of the intercellular spaces can vary among species and environmental conditions, affecting the rate of gas exchange and photosynthetic efficiency. The tissue works in concert with the palisade mesophyll, stomata, and vascular tissues to optimize leaf function.

See also: chlorenchyma, mesophyll, leaf anatomy, palisade parenchyma.