What is Leaf?
The leaf is a lateral and flattened structure borne at the node of the stem, bearing a bud in its axil.
The leaves originate from shoot apical meristems and are arranged in an acropetal order. Each axillary bud later develops into a branch. The structure of a leaf can be identified with its three distinct parts, namely, leaf base, petiole, and lamina.
What is Leaf base? The leaf is attached to the stem by the leaf base bearing two lateral small leaf-like structures called stipules. The leaf base may extend to become a sheath covering the leaf base in monocotyledonous plants or may become swollen (called pulvinus) in leguminous plants.
What is Petiole? The main function of the petiole is to help hold the blade to light, and for the leaves to perform photosynthesis. Petioles also allow the leaf to flutter in wind, thus bringing fresh air to the leaf surface.
What is Lamina? The lamina is the green flattened part of the leaf comprising veins and veinlets. A middle thick, prominent vein is called a midrib. The purpose of veins is to maintain the rigidity of the lamina and also acts as a channel to transport water, mineral, food materials, and wastes. The shape, margin, apex, surface, and extent of incision of lamina vary from species to species.
What is the function of the leaf? The leaf is the most essential vegetative organ for conducting photosynthesis due to the presence of a green pigment called chlorophyll. Photosynthesis takes place in the presence of sunlight, water, and carbon dioxide.
A. Parts of a leaf B. Reticulate venation C. Parallel venation
What is Venation?
Venation is defined as the arrangement of veins and veinlets in the lamina of a leaf. Venation is mainly of two types, reticulate and parallel. A network-like formation of veins is termed reticulate venation.
This type of venation is characteristic of dicotyledonous plants. When the veins run parallel to the midrib, then the arrangement is called parallel venation. This type of venation is characteristic of monocotyledonous plants.
