Leaf performs following functions:
1. Photosynthesis - Leaves manufacture food in the presence of sunlight.
2. Exchange of gases - Stomata help in exchange of gases which are important for respiration and photosynthesis.
3. Transpiration - Evaporation of excess of water in vapour form takes place through stomata which helps in ascent of sap and cooling of leaf surface.
4. Guttation - Exudation of excess of water containing salts takes place in liquid form from leaf margins in plants growing in humid climate.
5. Modifications for special functions - In certain plants leaves perform functions like manufacturing and storing food, providing support and protection, vegetative propagation and trapping insects.