T.S. of dicot leaf (Eg: Helianthu The T.S. of dicot leaf shows three regions namely epidermis, mesophyll and the vascular bundles.
(i) Epidermis:
This layer is present on both upper and the lower surface of the leaf. It is composed of single layer of cells with deposition of cuticle. There are openings on the lower epidermis called stomata surrounded by the guard cells. The stomata open into an air space.
(ii) Mesophyll:
It is the tissue lying between the upper and the lower epidermis. It is further divided into two regions namely palisade parenchyma and spongy parenchyma. Palisade jarenchyma has about three layers of cells, which are tubular. These cells lie below the upper epidermis. There are air spaces here and there. Spongy parenchyma is composed of loosely arranged irregular cells. There are few layers of cells below the palisade parenchyma. Both palisade and spongy parenchyma cells contain abundant chloroplasts and help in photosynthesis.
(iii) Vascular bundles :
These are conjoint, collateral and closed type. These are present in the midrib and vein regions. There is bundle sheath composed of parenchyma cells surrounding each vascular bundle. The cells are without chloroplasts. In the midrib region below the epidermis, there are collenchyma and parenchyma cell forming bundle sheath extensions.
