Structure of a Leaf

A leaf is a plant’s green, flat lateral protrusion. They vary in a variety of shapes, sizes, and colours, and are normally flattened and thin dorso-ventrally. Because they contain chlorophyll, they are the primary organ for photosynthesis. The kitchen of the plant is referred to as a leaf. This is due to the fact that they are the primary organ responsible for photosynthesis, which is how the plant obtains its energy, or food. The presence of chlorophyll gives them their green hue. 

Parts of a leaf:

Leaf consists of two main parts as follows:

The leaf blade:

It’s also known as the lamina. It’s usually wide and flat. Photosynthesis takes place at this layer. It has a prominent midrib, which is the major vein, in the centre of the leaf blade. The midrib gives rise to veins, which are branches that emerge from the midrib. They come in a variety of shapes and sizes, based on the type of edges, vein pattern, and number of blades per leaf. 

The petiole:

The stalk-like structure that joins the leaf blade to the stem is known as the rachis. The veins on the leaf blade are connected to the stem by small tubes in the petiole. A few of them deliver water to the leaf, while others transfer food from the leaf to other parts of the plant. 

Stipules:

Stipules are another component seen on some plants. At the base of the petioles, there are little flap-like structures. They are protective in some plants because they guard the growing petiole, while they fall off in others once the petiole begins to grow. 

Types of leaves:

Simple and compound leaves are divided into several groups depending on their shape, size, placement on the stem, leaves of flowering and non-flowering plants, and other physical characteristics. There are two types of leaves found on a plant: 

Simple leaf:

The leaf is said to be simple when only one lamina is attached to the main stem by a petiole. A basic leaf can be carved to any depth except the midrib or petiole. Guava leaves, for example. 

Compound leaf:

A leaf with two or more leaflets is known as a compound leaf. The leaf’s midrib is branched into different leaflets and joined by a single petiole in a complex leaf. Pea, for example, or palm leaves. 

The following types of leaves are subdivided from compound leaves: 

• Palmately compound leaf:

The leaflets of a palmately complex leaf are linked to the petiole at the tip. Silk cotton, for example. These can be classified as follows: 

• Unifoliate
• Bifoliate
• Trifoliate
• Quadrifoliate
• Multifoliate

• Pinnately compound leaf:

The midrib of a pinnately compound leaf is divided into several leaflets that are all connected by a common axis. Take, for example, Neem. These can be further classified as follows: 

• Pinnate
• Unipinnate
• Bipinnate
• Tripinnate
• Decompound
• Paripinnate
• Imparipinnate

Structure of a leaf:

The layers of each leaf are as follows: 

Epidermis:

The cuticle is a waxy substance secreted by the outermost layer. The cuticle aids in the retention of water within the leaf cells. The guard cells, which govern the flow of water into and out of the cell, are found in the epidermis. Guard cells do this by regulating the size of pores known as stomata. 

Mesophyll:

The leaf’s middle layer is made up of this. Depending on the type of cells discovered, it is divided into two layers: palisade and spongy mesophyll layers. The chloroplasts are discovered in this stratum. Chloroplasts are cell organelles that contain chlorophyll, an essential component of photosynthesis. The irregularly distributed spongy mesophyll cells contain the leaf’s vascular components. 

Vascular tissue:

The vascular tissue of the leaf is located in the veins. Xylem and phloem make up the vascular tissues, which are responsible for transporting water and food. 

Conclusion:

Photosynthesis is the principal function of the leaf, which converts carbon dioxide, water, and UV light into sugar (e.g., glucose) (shown below). The simple sugars produced by photosynthesis are then converted into different macromolecules (e.g., cellulose) that are needed to build the plant cell wall and other structures. As a result, the leaf must be very specialised in order to combine carbon dioxide, water, and UV radiation.