Leaves are green, thin flattened lateral outgrowths of the stem. They are borne at the nodes of the stem. Leaves are the chief organs of photosynthesis. The green leaves of the plant are collectively called as foliage of the plant.
Parts of a Leaf The three main parts of a typical leaf are
1. Leaf base
Leaf base : The part of the leaf which is attached to the stem or a branch is called leaf base. In some plants the leaf has a swollen leaf base. It is known as pulvinus eg. The compound leaves of the family Fabaceae.
In monocots the leaf base is very broad and flat and it clasps a part of the node of the stem as in maize and in banana. It is called sheathing leaf base.
Stipules: In most of the dicotyledonous plants, the leaf-base bears two lateral appendages called the stipules. Leaves which have the stipules are called stipulate.
The leaves without stipules are called exstipulate. The main function of the stipule is to protect the leaf in the bud.
Petiole : Petiole connects the lamina with the stem or the branch. A leaf is said to be petiolate when it has a petiole. It is said to be sessile when the leaf does not have a petiole.
Leaf blade: It is also known as lamina. This is the most important, green part of the leaf which is mainly concerned with the manufacture of food. The lamina is traversed by the midrib from which arise numerous lateral veins and thin veinlets.