The main function of the spongy layer inside the leaf is the diffusion of carbon dioxide gas through the air spaces found in this region. The spongy layer is part of the mesophyll and consists of irregular-shaped cells and air spaces. Inside the leaf, the mesophyll is the central part that is composed of the palisade and spongy mesophyll.
The function of the palisade mesophyll layer is the absorption of light because this layer also has many more chloroplasts that the spongy mesophyll. Besides the chloroplasts, some other structures found inside the leaf are the upper and lower epidermis and guard cells, which also have chloroplasts. The guard cells are found around a stoma and regulate the stoma's opening or closing to facilitate gas exchange.
The outer part of the leaf consists of veins, leaf blade and stomata. The exchange of carbon dioxide gas and other substances in the leaf occurs through the stoma, which is a tiny aperture also found on the leaf surface.
Some other important features associated with leaf structures are the xylem and phloem, which are found in the vascular bundle. The phloem transport different nutrients from the leaf to the rest of the plant. The xylem carries water and other nutrients from the root to the leaves.