Leaves are thin, flattened and usually green organ that grows at the stem of the plant. It is an essential part of shoot system for it is where the photosynthesis takes place and produces glucose as food for the plant.
Main parts of the leaf:
- The main parts of the leaf is consist of three parts namely leaf base, petiole, and lamina.
Leaf base - is the slightly expanded area where the leaf attaches to the stem and it contains two small leaf-like structure called stipules.
Petiole - is a stalk that attaches the leaf base to the stem.
Lamina - is also known as leaf blade. It is a flat surface of the leaf that contains midrib and veins. In addition, it is known as the photosynthetic surface of the plant.
Venation:
- It is the arrangement of veins and veinlets that can be found at the leaf blade or lamina.
Reticulate venation - are described as net-like veins because the arrangement of veins are scattered randomly.
Parallel venation - are described as parallel-like veins by which the arrangement of veins are parallel to each other.
Types of leaves:
- There are two broad categories of leaves and those are the simple and compound leaves.
Simple leaf - is when only one lamina is connected to the main stem by a petiole.
Compound leaf - is composed of two or more leaflets on one stalk.
Types of compound leaf:
- The compound leaf is further divided into two sub-categories which are the palmately and pinnately compound leaves.
Palmately compound leaf - is a leaf whose leaflets are attached at the tip of petiole.
Pinnately compound leaf - is a leaf whose midribs are divided into numerous leaflets and connects to one axis.
Phyllotaxy:
- It is the arrangement of leaves in the stem.
Alternate - is when one leaf develops at each node alternatively.
Opposite - is when a pair of leaves develops opposite to each other.
Whorled - is when two or more leaves develops at one common node.
Modification of Leaves:
- Leaves are modified in order to survive within its own environment. Each of the modification has its own function such as protecting itself, storage of food, support, and etc.
Storage leaves - thick and succulent leaves that stores water.
Leaf tendrils - it is a thread-like structure that found at the tip of the leaf.
Scale leaves - thin, membranous structures, without stalks, brownish or colourless in appearance.
Phyllode - petiole becomes flattened, taking the shape of a leaf and turns green.
Insectivorous leaves - the leaf is modified to catch and digest insects.
Functions of leaves:
- leaves performs different functions in order to help the plant live and survive and those are photosynthesis, transpiration, guttation, and storage.
Photosynthesis - is where the light energy from sunlight absorbs and converts it into chemical energy that produces glucose as byproduct. Also, this process is where the oxygen is released and the carbon dioxide is absorbed.
Transpiration - is a process where the stromata is opened to remove excess water from the plant.
Guttation - is contradictory to transpiration by which the stromata is closed to remove excess water from the xylem at the edges of the leaf.
Storage - leaves store water and nutrients for photosynthesis to happen.