Identifying characteristics of the internal structure of dorsiventral or dicot leaf:
(i) It is green, compressed with a wide lamina.
(ii) Leaf-blade is enriched with reticulate venation.
(iii) Mesophyll tissue is present and is composed of palisade parenchyma and spongy parenchyma. It is noticeably differentiated into palisade and spongy parenchyma. It is composed of elongated cells arranged in two layers. Spongy parenchyma area is present just underneath the palisade and extends up to the lower epidermis. The cells of spongy parenchyma are droopily set, filled with many chloroplasts and leave big intercellular spaces. The mesophyll cells contain a number of chloroplasts.
(iv) The vascular system includes vascular bundles found in the veins and the midrib. Vascular bundles are conjoint and closed i.e. cambium is absent in the vascular bundle. Vascular bundles are surrounded by one layered cells of thick-walled known as bundle sheath. The size of the vascular bundles is reliant on the size of the veins. These cells disrupt the palisade layers and are said to be the extensions of the bundle sheath.
(v) Stomata are present in the lower epidermis. A thick cuticle is present on the outer walls of epidermal cells. Each stoma is encircled by two bean-shaped cells called guard cells, which is dependable for the opening and closing of stomata. Each stoma opens into an air chamber.
(vi) Palisade parenchyma is present towards the upper epidermis while spongy parenchyma is present towards the lower epidermis. One-celled thick upper and lower epidermal layers consist of barrel-shaped, densely arranged cells.
(vii) The epidermis which covers both the upper surface and the lower surface of the leaf has a conspicuous cuticle. The tissue between the upper and the lower epidermis is called mesophyll which surrounds chloroplast and assists in photosynthesis.
(viii) Palisade cells are set at a flat at a right angle to the upper epidermis, and the chloroplasts in them are arranged along their radial walls.
(ix) The xylem is present towards the upper epidermis and consists of vessels and xylem parenchyma. Phloem is located is present towards the lower epidermis and consists of sieve tubes, companion cells, and phloem parenchyma.
