What Is Mesophyll?

Mesophyll is the material that makes up the majority of a plant's leaves. It is a relatively simple organic compound that is extremely important and is chiefly responsible for making plant life as we know it possible. The function and significance of mesophyll within a plant's leaves is something about which very few laypeople ever learn.

Identification

Mesophyll comprises the majority of the interior of a leaf. The exterior "skin" of the leaf is called the epidermis and is responsible for protecting the leaf from physical damage and from excessive moisture loss. The majority of the material found within the epidermis, with the exception of the leaf veins, is mesophyll. Indeed, anything in the leaf that is not vein or epidermis falls under the category of mesophyll. There are, however, certain sub-categorizations.

Types

There are two major types of mesophyll material found within leaves. These types are formed in distinct layers within the leaf. The first of these two layers, which lies on the outside close to the epidermis, is referred to as the palisade layer. The palisade layer of mesophyll is comprised of tightly packed cells containing many chloroplasts. The second subtype, the so-called spongy layer, is a less densely packed material with a great deal of air in-between cells. It also contains far less chloroplasts than the other type of mesophyll.

Function

Mesophyll has several different important functions within a leaf's basic structure. First of all, it is the area of the leaf in which the majority of photosynthesis takes place. It is also where the plant absorbs the majority of its necessary carbon dioxide, which has been let through the epidermis but is not actually absorbed there in great quantity. A plant's mesophyll is also responsible for storing energy and nutrients until they can be transmitted to the veins in the leaf and sent elsewhere in the plant where they are needed.

Significance

The significance of mesophyll cannot be easily overstated. Because mesophyll is responsible for photosynthesis to take place in large plants on any appreciable scale, it can be fairly stated that it is the key to plant life on Earth. Without photosynthesis human beings and all other forms of life as we know it could simply not exist. That is just how important mesophyll is. Without it life on Earth would be a completely different, unimaginable thing.

Geography

The exact manner in which any given plant's mesophyll functions is somewhat dependent on physical geography, more particularly on climate. In climates of extreme heat and sun exposure, most plants develop leaves that have multiple palisade layers of mesophyll and less spongy mesophyll. This is to maximize the photosynthesis capabilities of the plant and to insulate the interior spongy layer from excessive ultraviolet radiation. In colder climates with less sun exposure the exact opposite happens, and the leaves develop only one thin palisade layer of mesophyll and more spongy mesophyll within the interior of the leaves.

Resources

• More Information on the Anatomy of Leaves