`star` Introduction
`star` Parts of a leaf
`star` Venation
`star` Types of leaves


● The leaf is a `color{Violet }"lateral"`, generally `color{Violet }"flattened"` structure borne on the stem.

● It develops at the `color{Violet }"node"` and bears a `color{Violet }"bud"` in its `color{Violet }"axil"`.

● The `color{Violet }"axillary bud"` later develops into a branch.

● Leaves originate from `color{Violet }"shoot apical meristems"` and are arranged in an `color{Violet }"acropetal"` order.

● They are the most important `color{Violet }"vegetative organs for photosynthesis"`.


●A typical leaf consists of three main parts:

`star` `color{Brown}"Leaf Base"`
● The leaf is attached to the stem by the `color{Violet }"leaf base"`.

● It may bear two `color{Violet }"lateral small leaf like"` structures called `color{Violet }"stipules"`.

● In `color{Violet }"monocotyledons"`, the leaf base expands into a `color{Violet }"sheath"` covering the stem partially or wholly.

●In some `color{Violet }"leguminous plants"` the leaf base may become `color{Violet }"swollen"`, which is called the `color{Violet }"pulvinus"`.

`star` `color{Brown}"Petiole"`
●The `color{Violet }"petiole"` help hold the `color{Violet }"blade to light"`.

● Long thin flexible petioles allow leaf blades to `color{Violet }"flutter in wind"`, there by `color{Violet }"cooling the leaf"` and bringing `color{Violet }"fresh air"` to leaf surface.

`star` `color{Brown}"Lamina"`
● The `color{Violet }"lamina"` or the `color{Violet }"leaf blade"` is the green `color{Violet }"expanded part"` of the leaf with veins and veinlets.

● There is, usually, a `color{Violet }"middle prominent vein"`, which is known as the `color{Violet }"midrib"`.

● Veins provide `color{Violet }"rigidity"` to the leaf blade and act as `color{Violet }"channels"` of transport for water, minerals and food materials.

●The shape, margin, apex, surface and extent of incision of lamina varies in different leaves.


● The `color{Violet }"arrangement"` of veins and the veinlets in the lamina of leaf is termed as `color{Violet }"venation"`. It is of two types:

`star` `color{Brown}"Reticulate"`:
● When the veinlets form a `color{Violet }"network"`, the venation is termed as `color{Violet }"reticulate"`.

● Leaves of `color{Violet }"dicotyledonous plants"` generally possess reticulate venation

`star` `color{Brown}"Parallel"`:
● When the veins run `color{Violet }"parallel"` to each other within a lamina, the venation is termed as `color{Violet }"parallel"`.

● Parallel venation is the characteristic of most `color{Violet }"monocotyledons"`.


● `color{Brown}"Simple"` : A leaf is said to be simple, when its `color{Violet }"lamina is entire"` or when `color{Violet }"incised"`, the incisions do not touch the midrib.

● `color{Brown}"Compound"` : When the incisions of the lamina `color{Violet }"reach up to the midrib"` breaking it into a number of leaflets, the leaf is called compound.

●The compound leaves may be of two types :

`star` In a `color{Brown}"Pinnately compound leaf"` a number of leaflets are present on a `color{Violet }"common axis"`, the `color{Violet }"rachis"`, which represents the `color{Violet }"midrib"` of the leaf as in `color{Violet }"neem"`.

`star` In `color{Brown}"Palmately compound leaves"`, the leaflets are attached at a `color{Violet }"common point"`, i.e.,at the tip of petiole, as in `color{Violet }"silk cotton"`.

● A `color{Violet }"bud"` is present in the `color{Violet }"axil"` of petiole in both simple and compound leaves, but not in the axil of leaflets of the compound leaf.