The spongy layer of a leaf features small air spaces between cells that allow for the exchange of gases in photosynthesis. Together with the palisade, the spongy layer makes up the mesophyll of the leaf.
Spongy cells of the leaf are loosely packed together and lie between the palisade and the lower epidermis with the air spaces connected to each other and the outside by stomata. The spaces between cells create a larger surface area. The cells release water vapor and oxygen and pick up carbon dioxide during the day. It is also believed that the spongy layer acts as a temporary storage space for sugars and amino acids that have been synthesized in the palisade layer.