Internal structure of Isobilateral Leaf (Monocot Leaf)

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Isobilateral leaves of Paddy (Oryza sativa)
Image source: MB Chand

Here, I am posting a concise description of the anatomy of isobilateral leaf or monocot leaf.

Isobilateral leaves are found in monocotyledonous plants, such as maize. These leaves are normally erect and identical. Both the surfaces of such leaves are equally exposed to light. They are also called unifacial leaves. The internal structure of isobilateral leaf has epidermis, mesophyll tissue, and vascular bundles (see Figure 17).

1. Epidermis

Epidermis is the single layer of parenchyma found in both sides of leaf. This layer contains nearly equal number of stomata on both the sides, called amphistomatic. Each stoma opens into the substomatal cavity. In maize, cells in the upper stomata are modified into swollen bulliform or motor cells. Each stoma is guarded by a pair of dumb-bell shaped guard cells.

2. Mesophyll tissue

Mesophyll tissue is between the upper and lower epidermis. It contains large rounded parenchymatous cells with large cavities. It has reduced intercellular spaces. It is differentiated into palisade parenchyma and spongy parenchyma. Cells have abundant chloroplast.

3. Vascular bundles

Vascular bundles are parallelly arranged within the mesophyll tissues. They have different sizes. Each vascular bundle is conjoint, collateral, and closed type. Also, it is surrounded by a bundle sheath. Small vascular bundles are with less developed phloem and xylem whereas large bundles are with distinct phloem and xylem. The phloem is towards the lower epidermis and xylem is towards upper epidermis.

Phloem consists of sieve tubes and companion cells to transport food materials.

Xylem consists of two pitted oval metaxylem with tracheids in between them. The xylem parenchyma is less abundant. The protoxylem remains as a lysigenous cavity. Xylem conducts water and minerals.

Figure 17 T. S. of isobilateral leaf