Define a Leaf

The leaf always develops from the node of the stem. It may be scaly or usually green, dorsoventrally flattened , having limited growth and life span. The green colour of the leaves is due to chloroplasts in most of its cells. A typical leaf consists of a leaf base, petiole, stipules and lamina. The leaf is called petioate when the petiole is present. e.g. leaf of sunflower. The leaf is called sessile when he petiole is absence. e.g. leaf of maize.
Normal Functions of Leaf
The leaves synthesize organic foods through photosynthesis due to a large number of chloroplasts therein. They lose a large amount of water by way of transpiration though stomata. They also perform gaseous exchange though stomata for respiration.