Functions of Leaf

Leaf is any green flattened outgrowth from the stem of a plant. Because the initial sites of photosynthesis, leaves produce food for plants that successively nourishes and sustains all land animals. They’re connected by an integral system to the remainder of the plant so as the free exchange of nutrients, water, and finish product of photosynthesis (oxygen and carbohydrates in particular) may be carried to its numerous parts. Leaves are initiated within the top bud (growing tip of a stem) along with the tissues of the stem itself. Few organs that are completely different from the standard leaf are shaped within the same manner and are literally changed leaves; among these are the sharp spines of cacti, the needles of pines and alternative conifers, and therefore the scales of an asparagus stalk or a liliaceous plant bulb.

Leaf Function

The most Important and basic function of a leaf is to provide food for the plant by the process of photosynthesis. Chlorophyll, the substance that provides plants their characteristics green colour, absorbs light energy. The inner structure of the leaf is protected by the leaf epidermis that is continuous with the stem epidermis. The centre part of the leaf leaf, or mesophyll, consists of soft-walled, un-specialised cells of the kind called parenchyma. The oxygen released from inexperienced leaves replaces the oxygen from the atmosphere by plant and animal respiration and by combustion. The hydrogen obtained from water is mixed with carbon dioxide gas within the protein processes of photosynthesis to make the sugars that are the basis of each plant and animal life. Oxygen is passed into the atmosphere through stomata—pores within the leaf surface.

Parts of a Leaf

Leaves have 2 main parts: 

The leaf blade: it is also referred to as the lamina. It’s typically broad and flat. It is in this layer that photosynthesis happens. It contains a distinguished midrib at the middle of the leaf that is the main vein. From this midrib arise branches referred to as veins. They’re of various varieties relying upon the kind of edges, the pattern of the veins and therefore the range of blades per leaf.

The petiole: it looks like a stalk that connects the leaf to the stem. The stalk has small tubes that connect the veins on the leaf to the stem. Some of them let water transport to the leaf whereas other carry food far away from the leaf to other components of the plant.

Few plants also has another part referred to as stipules. These are little flap-like structures that grow at the bottom of the petioles. They’re protecting in some plants after they defend the growing stalk whereas in others, they fall off once the stalk starts growing.

Types of Leaves

Leaves may be classified on several anatomic and morphologic features:

Based on Blade

• Simple Leaf- the lamina or the leaf is un-partitioned. Though there are little divisions, they are not able to reach the midrib and divide the lamina

• Compound Leaf- The leaf is split from the midrib into 2 or additional parts. Generally these divided parts operate as separate leaves

Based on form of the Blade

• Elliptical

• Lanceolate

• Linear

• Ovate

• Cordate

Based on the Existence or Non-existence of the petiole (stalk)

• Petiolated- These leaves have a petiole or stalk that attaches them to the stem

• Sessile- These leaves don’t have a petiole and are directly connected to the stem

Based on the serration on the sting of the leaf

• Serrate: Have saw-teeth formed margins

• Lobed: the leaf blade is split however the division doesn’t reach the midrib

• Smooth: this kind of leaf margin is named ‘entire’ leaf margin and is sleek all around

• Sinuate: Have sleek curves on the margins

• Dentate: they need teethed margins

Based on the arrangement of veins

• Parallel: The veins on the leaf run parallel to every alternative maintaining identical distance throughout

• Palmate: The veins originate at some extent and diverge from the purpose like the palm of the hand

• Pinnate: there’s a nervure that is present within the middle of the leaf. From this midrib arise the lateral veins

Based on their arrangement on the stem

• Alternate: every leaf arises from a separate node on the stem at completely different levels

• Opposite: every node provides rise to 2 leaves, one on either side placed oppositely

• Whorled: during this arrangement, many leaves are present at identical level round the stem giving it a whorled look

• Rosulate: The leaves organize themselves during a ring-like pattern round the stem

Structure of a leaf

Every leaf consists of the following layers.

• Epidermis: it’s the outer layer and secretes a waxy substance referred to as the cuticle. The cuticle helps retain water within the leaf cells. The stratum homes the guard cells that regulate the movement of water into and out of doors the cell. Guard cells do thus by dominant the dimensions of the pores conjointly referred to as stomata

• Mesophyll: This comprises of the centre layer of the leaf. It’s differentiated into 2 layers depending on the kind of cells found: palisade and spongy mesophyll layers. It’s during this layer that the chloroplasts are found. Chloroplasts are cell organelles that contain chlorophyll that is needed for photosynthesis

• Vascular Tissue: The plant tissue is primarily found within the veins of the leaf. The vascular tissues are composed of xylem and phloem that are responsible for the transport of water and food

Conclusion

Thus the main functions of the leaf is photosynthesis, transpiration, guttation, storage and defense for the plant, leaves are generally made of a distinct upper and lower surface, all the leaves are generally found above the ground but some resides beneath the ground.