External Structure of Leaf

A leaf is an organ of the plants which is usually found above the ground ground. Leaf plays an important role in the process of photosynthesis. All the leaves found in the world are flat in structure,this is because flat structure of leaf helps them during the photosynthesis process. Due to its flat structure it absorbs more carbon dioxide and releases more oxygen during the process of photosynthesis. Leaf is a place where transpiration takes place. Food and water can also be stored in the leaves. Some times leaves changes to the plants.

Anatomically leaf is divided into three parts

• Petiole 
• Lamina 
• Stipules

Petiole also known as leaf stalk. lamina is also known as leaf blade.and the stipules is located to the both sides of petiole. Leaf is an organ of a plant and it contains some tissues which are very important for the proper functioning. The tissue which covers the upper and lower part is known as epidermis. An interior tissue known as mesophyll. And a vascular tissue. The outer layer of cells which cover the leaf is known as epidermis, it acts as barrier between the plants inner parts and the outer world. It helps to control the loss of water, process is known as transpiration. It also contains some differentiated cells like epidermis , guard, subsidiary cells and the epidermis hair. It is covered by the pores known as stomata. Most of the parts between upper and lower parts of the epidermis is covered by a tissue known as mesophyll. This tissue also known as assimilation tissue is major place for the photosynthesis.

This mesophyll is divided into two layers

• Palisade layer 
• Spongy layer

Palisade layer is the upper layer and the spongy layer is just below the palisade layer. These layers are not found in all the plans. It is absent in the marshy and aquatic plants. Generally leaves are green in colour, this is because of the chlorophyll. The vascular tissue is present in the veins and it is mainly found in the spongy layer of the mesophyll.

The veins contains mainly two parts

• Xylem 
• Phloem

Xylem and phloem is responsible for the transfer of foods and water in the different parts of the leaves.

External Structure of Leaf.