Question

Describe the internal structure of dicot leaf with the help of diagram.

Answer 1

The internal structure of dicotyledonous leaves reveals epidermis, mesophyll and vascular tissues.

(i) Epidermis: A dicotyledonous leaf is generally dorsiventral. It has upper and lower epidermis. The epidermis is usually made up of a single layer of cells that are closely packed. The cuticle on the upper epidermis is thicker than that of lower epidermis. The minute openings found on the epidermis are called stomata.

(ii) Mesophyll: The ground tissue lying between the two epidermal layers is known as the mesophyll. It is differentiated into (a) Palisade parenchyma and (b) Spongy parenchyma.

(a) Palisade parenchyma: Palisade cells occur below the upper epidermis. In consists of one layer of elongated cylindrical cells. They are closely packed. They contain numerous chloroplasts. It manufactures starch by photosynthesis.

(b) Spongy parenchyma: It consists of irregularly shaped cells, loosely arranged towards the lower epidermis. They enclose large intercellular spaces and air cavities. The cells contain a few chloroplasts. Spongy cells help in the diffusion of gases through the spaces between them.

(c) Vascular tissues: It is located in the veins. Vascular bundles are conjoint, collateral and closed. Each vascular bundle is surrounded by a compact layer of thin-walled parenchymatous cells. This layer is known as border parenchyma or bundle sheath.