The leaf is a dorso-ventrally compressed, lateral appendage of the stem, produced at the nodes.
There are main three parts of the leaf that are as follows,
- Leaf Base
Parts Of Leaf –
The part of the leaf which is attached to the stem or a branch is called the leaf base. Some plants ‘ leaves have a swollen base. It is known as pulvinus eg. The compound leaves the family Fabaceae. In monocotyledonous main leaf is very wide and flat, and the press, part, node as the corn root, of course. It is called sheathing leaf base.
The main leaf is another area where the leaf attaches to the corner of the stem. Paired stipules involved are usually found on both sides of the main leaf and can be seen as scales, spines, or glands…
The main functions of Leaf Base are to protect the bud and carry out photosynthesis. In monocotyledons, the leaf base expands into a sheath covering the stem partially or completely covering the root.
In some leguminous/bean leaves plants, the leaf base may become swollen, which is said to be the pulvinus. It protects the young axillary bud.
Petiole connects the lamina to the stem or the branch. A leaf is said to be a petiolate leaf when a leaf has a petiole. The leaf is said to be sessile when it does not have a petiole.
The petiole is a stalk present on a leaf base that attaches a leaf to the plant stem. In petiolate leaves, the leaf stalk (petiole) can be longer, as in the leaves of celery and rhubarb, short or completely absent, in which case the blade attaches directly to the stem and is said to be sessile. Subpetiolar leaves have a shorter petiole, may appear sessile. The broomrape family Orobanchaceae is of an example of a family in which the leaves are always sessile.
Leaf Petiole provides a connection from the stem to permit sap to enter the leaf and the products of photosynthesis (carbohydrates) to be transported from the leaf to the rest of the plant.
Leaf Lamina is also known as a leaf blade. This is the most important thing in the green part of the leaf is mainly used in food production. The lamina is traversed by the midrib from which arise numerous lateral veins and thin veinlets.
The primary function of the lamina is photosynthesis.
Leaf lamina is also known as Leaf Blade.
Phyllotaxy in Leaves of Plants
- Phyllotaxy is nothing but the arrangement of leaves on the stem.
- The term phyllotaxy was first introduced by Charles Bonnet to describe the arrangement of leaves on a plant.
There are main 3 types of phyllotaxy in leaves,
Alternate or Spiral phyllotaxy is the simplest type of phyllotaxy in which a single leaf on each node is present.
Opposite phyllotaxy is a type in which two leaves arise from the stem at the same node, on opposite sides of the stem.
Whorled phyllotaxy is a type in which more than two leaves arise from a single node.
Types of Leaves in Plants
There are mainly two types of leaves as follows,
Simple leaves are those leaves in which a single leaf blade or lamina is present.
Compound leaves are those in which the leaf blade or lamina is divided into a number of segments are known as leaflets or pinnae.
Venations in Leaves
The specific arrangement of veins and veinlets in the lamina is known as venation in the leaf.
The venation is mainly of two types,
- When the veins and veinlets form a network-type structure it is called reticulate venation.
- Here the midrib is centrally placed and veins and veinlets remain distributed laterally.
- It is found in dicotyledonous plants.
- When the veins and veinlets form a network it is called reticulate venation. Here the midrib is centrally placed and veins and veinlets remain distributed laterally.
- They are with a single mid-vein.
- e.g. Mango
- They are with two or more prominent veins.
- It may be convergent or divergent.
- e.g. Zizyphus
In this type of venation veins in the lamina run almost parallel to one another.
- Having only one principle vein that gives off many lateral veins which proceed towards the margin or apex of the leaf blade in a more or less parallel manner.
- e.g. Banana.
- Having many principal veins arising from the tip of the petiole and proceeding upwards or outwards.
- Many principal veins arising from the base of the leaf blade coverage towards its apex or less parallel manner.
- e.g. Grasses, Wheat, Bamboo.
- Many principal veins arising from the tip of the petiole, diverge from the tip of the petiole, diverge towards the margin of the leaf blade in a more or less parallel manner.
- e.g. Fan Palm.
Functions of Leaves
There are so many functions of the leaf. some functions are mention as follows,
The process of photosynthesis, the process by which green plants and some other organisms convert light energy into chemical energy.
Gas exchange is the process by which oxygen and carbon dioxide move between the bloodstream and the lungs.
Removal of excess water from the xylem at the edges of the leaves when the stomata are closed is known as guttation.
Leaves are a site of photosynthesis. Therefore, they store water and nutrients. The succulent and thick leaves particularly adapt to water storage.
The uptake of water at the roots, transport of water through plant tissues, and release of vapor by leaves are known as transpiration.
A leaf is made of many layers that are sandwiched between two layers of tough skin cells.