Question

Explain the structure of a leaf with the help of a labeled diagram.

Answer 1

Hint: A leaf is the main lateral appendage of the vascular plants that play an important role in photosynthesis and gaseous exchange. The origin of the leaf is exogenous and it develops from the leaf primordium of the shoot apex.

Complete answer:

-A leaf is a thin, green, flat, and expanded lateral attachment of stem which is located at a node with a bud in its axil. Due to the presence of photosynthetic pigment chlorophyll, the leaf appears green in color and these chlorophylls help the plants to synthesize organic food.
Structure of a leaf:
-Lamina: A leaf typically consists of a leaf blade called the lamina which is the widest part of the leaf. It performs various functions such as photosynthesis and transpiration.
Petiole: Some of the leaves get attached to the stem of the plant by the cylindrical like -structure petiole and the leaf with petiole is called petiolate. However, some leaves directly attached to plant stems are known as sessile leaves.
-Stipules: The stipules are the small lateral appendages located on either side of the leaf base. Leaves having stipules are called stipulate and without stipule are called exstipulate. Stipules are an essential part of the leaf as it protects the young leaf or leaf primordia.
-Phyllotaxy: The arrangement of leaves on a stem is called phyllotaxy. On the basis of arrangements, leaves are classified as either alternate, spiral, opposite, or whorled.

Note: -In coniferous plant species, leaves have adapted themselves into the reduced size and needle-like appearance to flourish in cold environments. These plants include spruce, fir, pine. etc.
-In hot climates, plants like cactus have adapted to form succulent leaves that help to preserve water.
-The aquatic plants have leaves with wide lamina that can float on the surface of the water. It consists of a thick waxy cuticle on the leaf surface that repels water.