Internal Structure of Dorsivental Leaf (mango leaf)
Dorsiventral leaves are found in dicots. The vertical section of a dorsiventral leaf contains three distinct parts: Epidermis, Mesophyll and Vascular system.
The epidermis is present on both upper surface (adaxial epidermis) and lower surface (abaxial epidermis) of the leaf has a conspicuous cuticle. Mesophyll tissue of the leaf present between the adaxial and abaxial epidermises. Vascular system includes vascular bundles, which can be seen in the veins and the midrib.
The transverse section of the leaf shows the following structures.
(i) Upper epidermis: The epidermis on the outside is covered with a thick cuticle. This is the outermost layer made of single-layered parenchymatous cells without intercellular spaces.
(ii) Lower epidermis: It is a single layer of parenchymatous cells with a thin cuticle. Abaxial epidermis bears more stomata than the adaxial epidermis. More number of stomata are present on the abaxial epidermis. It contains numerous stomata. Chloroplasts are present only in guard cells. The lower epidermis helps in the exchange of gases.
(iii) Mesophyll: Mesophyll is a tissue of the leaf present between the adaxial and abaxial epidermises. The tissue present between the upper and lower epidermis is called mesophyll. It is differentiated into Palisade parenchyma and Spongy parenchyma. Mesophyll contains the chloroplasts which perform the function of photosynthesis.
- Palisade parenchyma: It is found just below the upper epidermis. The cells are elongated. These cells have more number of chloroplasts. The palisade parenchyma is placed adaxially.
- Spongy parenchyma: It is found below the palisade parenchyma tissue. Cells are almost spherical or oval and are irregularly arranged. There are numerous large spaces and air cavities between the cells of spongy parenchyma.
(iv) Vascular bundles: Vascular bundle of mid-rib is larger. Vascular bundles are conjoint, collateral, and closed. The vascular bundles are surrounded by a layer of thick-walled bundle sheath cells. Each vascular bundle consists of xylem lying towards the upper epidermis and phloem towards the lower epidermis.
Major Internal Structure of Dorsivental Leaf are pointed below:
(i) It is green, compressed with wide lamina
(ii) Leaf-blade is enriched with reticulate venation
(iii) Mesophyll tissue is present and is composed of palisade parenchyma and spongy parenchyma
(iv) Vascular bundles are conjoint and closed; i.e. cambium is absent in the vascular bundle. Vascular bundle are surrounded by one layered cells known as bundle sheath
(v) Stomata are present on the lower epidermis
(vi) Palisade parenchyma is present towards the upper epidermis, while spongy parenchyma is present towards the lower epidermis.
