Morphology of a leaf - Practice Questions & MCQ

The Leaf and Its Parts

• The leaf can be defined as a lateral, generally flattened structure borne on the stem.
• It arises at the node. 
• It bears the bud in its axil called axillary bud.
• The axillary buds later develop into branches.
• The leaves arise from shoot apical meristem and are arranged acropetally.
• These are the important parts for the process of photosynthesis. 

Parts of the leaf:

A typical leaf consists of the following parts i.e. leaf base, petiole and lamina 

a) Leaf Base:

• The leaf base connects the rest of the leaf to the stem.
• It is also called the hypopodium.
• Two small leaf-like structures called stipules may arise from the leaf base.
• The leaves that bear stipules are called stipulate leaves while the leaves that do not bear stipules are called ex-stipulate leaves.
• Stipules are mainly concerned with photosynthesis and protection of bud.
• In monocot plants, the leaf base expands and covers the stem partially or wholly.
• In some plants of the family leguminosae, the leaf base becomes swollen and is called pulvinus. It protects the young axillary bud.

b) Petiole:

• It is also called the mesopodium.
• It is a smooth or grooved, cylindrical or sub-cylindrical stalk which attaches the leaf to the leaf base.
• It holds the leaf above the level of the stem.
• Leaves with petioles are called petiolate leaves.
• Leaves without petioles are called non-petiolate or sessile leaves.
• Papaya has hollow petiole.

c) Lamina:

• It is also called the leaf blade or the epipodium. 
• It is the expanded green part of the leaf that bears veins.
• The middle prominent vein is called the midrib.
• The veins act as channels for the conduction of water and photosynthates.
• The function of the lamina is to perform photosynthesis and transpiration.

TIP:

• The leaves of dicot plants are called dorsiventral because of structural differences between dorsal and ventral surfaces.
• The leaves of monocot are structurally identical in both surfaces, so these are called isobilateral leaves.