The Leaf

Lab -7- The Leaf
A leaf is an aerial and lateral outgrowth of the stem of a usually flat and dorsiventral anatomy. It functions mainly to manufacture food by photosynthesis and consists typically of a stalk also called petiole, a flattened blade, the lamina, and the leaf base. Strands of conducting and strengthening tissues, the veins, run through it. Their pattern, also called leaf venation, is a feature of characterization. Leaves may be simple, i.e. undivided or compound (composed of several parts called leaflets). The blade margin and the leaf arrangement at the stem are further features of characterization.

Simple Leaves :- Simple leaves have one leaf blade. The leaf may be irregularly shaped, but it is still one blade with one leaf stalk.

Compound Leaf :- Compound leaves are made of many individual leaflets that are all attached to the same leaf stalk

Modified Leaves :- Some leaves have many unusual shapes and sizes. This allows them to adapt to protect the plant, to store food, or to adapt to the environment in which they grow.

Leaf Arrangement
Alternate:- In an alternate arrangement, single leaves are attached spirally along the stem.
Opposite:- Two leaves emerge opposite each other on a stem.
Whorled:- In a whorled arrangement, several leaves emerge together around a stem node.

Leaf Tissues
The leaf blade’s outer surface is epidermal tissue and the ground tissue within is photosynthetic mesophyll, interspersed with “veins” (vascular bundles) of conducting (vascular) tissue. Vascular connections between blade and stem pass through the petiole.