12. Describe the internal structure of a dorsiventral leaf with the help of labelled diagrams.
The internal structure of a dorsiventral leaf-
The leaf lamina of a dorsiventral leaf has 3 parts: epidermis, mesophyll and vascular system.
1. Epidermis- The epidermis is two layered. The upper epidermis is called adaxial epidermis and the lower one is called abaxial epidermis. More number of stomata are present on the abaxial epidermis.
2. Mesophyll- Inner to epidermis, mesophyll tissue is present. There are two types of cells in the mesophyll i.e. palisade parenchyma and spongy parenchyma. The palisade parenchyma is placed adaxially while the spongy parenchyma is situated below the palisade parenchyma and extends to the lower epidermis. There are numerous large spaces and air cavities between the cells of spongy parenchyma.
3. Vascular system- The vascular bundles are surrounded by a layer of thick-walled bundle sheath cells. They are conjoint and closed.