Biology

Internal Structure of a Leaf

The internal structure of a leaf: Leaves are very important structures. They are the plant’s food factories. TheyInternal Structure of a Leaf labbeled diagram absorb sunlight energy to make food. Under a powerful microscope, we can see three main internal parts of a leaf, i.e. epidermis, mesophyll, and vascular bundle.

Epidermis

The upper layer of a leaf is called the upper epidermis. The lower of the leaf is called the lower epidermis. The lower epidermis has many stomata. Each stoma has an opening and two bean-shaped guard cells. The exchange of oxygen, carbon dioxide and water vapors between the leaf cells and the air take place through stomata.

Mesophyll

Between the upper and lower epidermis is the epidermis. The mesophyll is made of cells that contain chloroplasts. A green pigment chlorophyll is present in chloroplasts. Chlorophyll traps light energy which is used in the food-making process. The mesophyll is the region where the food making process called photosynthesis takes place.

Vascular Bundle

The central part of the mesophyll tissue is made of vascular bundles. Two types of tissues called xylem and phloem are present in the vascular bundle. Xylem carries water from roots to the leaves. Phloem carries prepared food to other parts of a plant.

Gaseous Exchange In Plants:

Plants have no organs or systems for the exchange of gases with the environment. Every cell of the plant body exchanges gases with the environment on its own.

The leaves and young stems have stomata in their epidermis. The gaseous exchange occurs through this stomata. The inner cells of leaves (mesophyll) and stems also have air spaces among them, which help in the exchange of gases in the Internal Structure of a Leaf.

Leaf cells face two situations. During the daytime when the mesophyll cells of leaves are carrying out photosynthesis and respiration side by side, the oxygen produced in photosynthesis is utilized in cellular respiration. Similarly, the carbon dioxide produced during cellular respiration is utilized in photosynthesis.

However, during the night when there is no photosynthesis occurring, the leaf cells get oxygen from the environment and release carbon dioxide through stomata.

In woody stems and mature roots, the entire surface is covered by bark which is impervious to gases or water. There are certain pores in the layer of bark. There are called lenticels. The lenticels allow air to pass through them.

Gases diffuse ion and out of the general surface of the young roots. The gases are found in the soil surrounding the roots.

The aquatic plants get the oxygen dissolved in water and release carbon dioxide in water

The young stems and leaves, some gaseous exchange also occurs through the cuticle which is present over their epidermis.

The internal structure of a leaf Video Explained


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