What is a leaf? Give the main parts of a leaf.

(N/A) $\rightarrow$ 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 a 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: The petiole helps hold the blade to light. Long,thin,flexible petioles allow leaf blades to flutter in the wind,thereby cooling the leaf and bringing fresh air to the 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.