mesofyl

The mesophyll, sometimes referred to as mesofyl in some languages, is the internal tissue of a leaf that lies between the upper and lower epidermis and is the principal site of photosynthesis. It consists mainly of chlorenchyma cells that contain chloroplasts and metabolize light energy to convert carbon dioxide into sugars. The mesophyll forms the bulk of the leaf interior and is organized to optimize light capture and gas exchange.

In many dicotyledonous plants, the mesophyll is divided into two distinct layers. The palisade mesophyll, located directly beneath the upper epidermis, consists of tightly packed, elongated cells rich in chloroplasts and is specialized for light absorption. Below this layer lies the spongy mesophyll, made up of more loosely arranged cells with extensive intercellular air spaces that facilitate diffusion of carbon dioxide, water vapor, and oxygen to photosynthetic cells. Veins and vascular tissue are interspersed within the mesophyll, supplying water and transporting the sugars produced during photosynthesis. In many monocots, the mesophyll is more uniform and lacks a clearly differentiated palisade and spongy zone.

Functionally, the mesophyll is the main site of photosynthesis and oxygen production in leaves. Its internal air spaces aid gas exchange, while the arrangement of cells and chloroplast density influence photosynthetic efficiency. The development and organization of the mesophyll are influenced by light, leaf shape, and environmental conditions, reflecting adaptations to diverse ecological niches.