Leaf Definition

The hatchet leaf describes the body organ that develops the key lateral appendage ~ above the stem of vascular plants. In general, leaves room thin, flat organs responsible for the photosynthesis that the plant. Return photosynthesis commonly only occurs on the upper surface ar of the leaf, it can happen on both sides in part plant species. Leaves are generally comprised of a unique upper and lower surface, stomata for gas exchange, waxy coating, hairs, and also venation. Each side the the sheet differs in about the level to which these attributes are expressed. Although pipeline are generally located above ground, some types have pipeline which reside underground (e.g., bulb scales) or underwater (e.g., aquatic tree species). Moreover, the pipeline of some plants may not be associated with photosynthesis (e.g., cataphylls). Leaves are commonly oriented ~ above a plant to protect against blocking the sunshine of the leaves situated underneath.

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Function of the Leaf

As one of the most necessary constituents the plants, leaves have actually several crucial functions:


The primary role of the leaf is the counter of carbon dioxide, water, and UV light into sugar (e.g., glucose) via photosynthesis (shown below). The simple sugars formed via photosynthesis are later on processed into various macromolecules (e.g., cellulose) forced for the formation of the tree cell wall surface and other structures. Therefore, the leaf should be highly dedicated to combine the carbon dioxide, water, and UV light because that this process. Carbon dioxide is diffused indigenous the atmosphere through specialized pores, termed stomata, in the external layer that the leaf. Water is directed to the pipeline via the plant’s vascular conducting system, termed the xylem. Leaves room orientated to ensure maximal exposure come sunlight, and are generally thin and flat in form to allow sunlight to pass through the sheet to reach the chloroplasts, which are specialized organelles that carry out photosynthesis. When sugar is formed from photosynthesis, the leaves role to carry it under the plant via devoted structures called the phloem, which operation in parallel to the xylem. The sugar is commonly transported come the roots and also shoots that the plant, to assistance growth.



Some pipeline have additionally evolved defense instrument to stop being consumed or damaged. Some examples encompass the spines that cacti, cap of gymnosperms, respectively. In addition, hairs discovered on leaves protect against water ns in dry climates and sting animals that detour herbivores (e.g., Urticaceae). Moreover, the waxy coatings uncovered on leaves serve to protect against water loss, rain, and also forms that contamination. Oils and other secreted substances likewise detract from gift consumed through herbivores.

Types of Leaf

In general, the species of leaf can be separated into six major types, although over there are likewise plants through highly specialized leaves:

Conifer Leaf

Conifer leaves are needle-shaped or in the form of scales. Conifer pipeline are frequently heavily waxed and highly adapted to chillier climates, i ordered it to dispel snow and also resist freezing temperatures. Some examples encompass Douglas firs and also spruce trees. The images below illustrate this kind of leaf.


Microphyll Leaf

Microphyll leaves are defined by a single vein that is unbranched. Although this kind of leaf is abundant in the fossil record, couple of plants exhibit this form of leaf today. Part examples incorporate horsetails and also clubmosses. The image below illustrates this form of leaf.


Megaphyll Leaf

Megaphyll pipeline are defined by lot of veins that deserve to be very branched. Megaphyll pipeline are large and flat, and generally comprise the leaf of most plant species. The image below illustrates this kind of leaf.


Angiosperm Leaf

Angiosperm leaves room those found on flower plants. These pipeline are identified by stipules, a lamina, and also a petiole. The illustration below shows an instance of one angiosperm leaves.



Fronds space large, split leaves characteristics of ferns and also palms. The blades can it is in singular or separated into branches. The image below presents an example of a frond.


Sheath Leaf

Sheath pipeline are usual of grass species and monocots. Thus, the leaves are long and also narrow, v a sheathing neighboring the stem at the base. Moreover, the vein framework is striated and each node has only one leaf. The image listed below presents an instance of a sheath leaf.



1. The primary duty of a leaf is: A. Water evaporation for cooling B. Photosynthesis C.

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carry out shade to the shoot and also root frameworks of the plant D. Transpiration