Page 1 - 4. The Leaf, Functions and modifications of leaves

SAI International School
Subject- Biology, Class-VI
Topic- The Plant World
Subtopic- The Leaf, Functions and Modifications of Leaves

Lesson Notes

The leaf

• The leaf is responsible for the process of photosynthesis in plants.
• Leaves differ in shape and size.

Parts of a leaf

• The flat broad part of the leaf is called the leaf lamina
• The lamina is attached to the stem by the stalk called the petiole of the leaf.
• There is a thick midrib with veins arising from it in the leaf lamina. They are
responsible for the transfer of water and mineral salts in the leaf.
• The veins are arranged in a specific pattern on a leaf. This arrangement of the veins
on a leaf is called venation.
• There are two types of venation- reticulate venation and parallel venation.

• Reticulate venation has a main vein running through the centre of the leaf with a
network of smaller veins and veinlets. They are found in dicots. Example mango,
kidney beans etc.
• When the veins run parallel to each other from the petiole to the tip of the leaf, the
venation is called parallel venation. This arrangement of veins in a leaf is seen in
monocots. Example grass, wheat, maize.

Functions of Leaves:

• Leaves prepare food for the plant using carbon dioxide and water in the presence of

sunlight and chlorophyll in the leaves. This process is called Photosynthesis.
• The stomata in the leaves facilitate exchange of gases for the process of respiration
and photosynthesis.
• The leaves also help in the process of transpiration (loss of water in the form of
vapour, from the aerial parts of the plant).
• The process of transpiration helps in

❖ Transportation of substances dissolved in the water absorbed by the roots.
❖ Maintain the temperature of the plant,
❖ Roots are able to steadily absorb water and mineral salts from the soil and
are able to conduct the same to the leaves for the process of photosynthesis
to happen.