What is leaf ? Give main parts of leaf.

$\rightarrow$ Leaf : The leaf is a lateral, generally flattened structure borne on the stem. It develops at the node and bears a bud in its axil.

$\rightarrow$ Leaves originate from shoot apical meristems and are arranged in an acropetal order.

$\rightarrow$ They are the most important vegetative organs for photosynthesis.

$\rightarrow$ Parts of leaf : A typical leaf consists of three main parts : Leaf base, petiole and lamina.

$\rightarrow$ Stipules : The leaf is attached to the stem by the leaf base and may bear two lateral small leaf like structures called stipules.

$\rightarrow$ In monocotyledons, the leaf base expands into a sheath covering the stem partially or wholly.

$\rightarrow$ Pulvinus : In some leguminous plants the leaf base may become swollen, which is called the pulvinus.

$\rightarrow$ Petiole : Petiole help hold the blade to light. Long thin flexible petioles allow leaf blades to flutter in wind, thereby cooling the leaf and bringing fresh air to leaf surface.

$\rightarrow$ Leaf blade : The lamina or the leaf blade is the green expanded part of the leaf with veins and veinlets. There is, usually, a middle prominent vein, which is known as the midrib. Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals and food materials.

$\rightarrow$ Types of Leaves : Shape, margin, apex, surface and incision of lamina is different in different leaves. According to that various types are formed.