Internal Structure of Dorsiventral Leaf (Dicot Leaf)

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Dorsiventral leaves of Syzygium cordifolia 

Image source: File:Dorsiventral leaves of Syzygium cordifolia IMG 1985.jpg - Wikimedia Commons

In this post, I am presenting a concise description of the anatomy of dorsiventral leaf .

The dorsiventral leaf is found in dicotyledonous plants. It has two surfaces – the upper or adaxial surface and the lower or abaxial surface. Its internal structure has epidermis, mesophyll tissues, and vascular bundles (See Figure 16).

1. Epidermis

Dorsiventral leaf shows distinct upper and lower epidermis.

Upper epidermis: The upper epidermis consists of a single layer of thin-walled and compactly arranged parenchymatous cells without intercellular spaces. Cells lack chloroplasts. Stomata are either absent or are fewer than in the lower epidermis. It is externally covered by cuticle.

Lower epidermis: Lower epidermis is made of single layer of parenchymatous cells. It is externally covered by cuticle. More stomata are present than on upper epidermis. Each stoma is surrounded by two kidney-shaped guard cells.

Epidermis helps in protection of the inner tissues from microbes, exchange of gases, and transpiration.

2. Mesophyll tissue

Mesophyll tissue lies between upper and lower epidermis. It is made of two types chlorophyll bearing parenchyma – palisade parenchyma and spongy parenchyma.

Palisade parenchyma: Palisade parenchyma lies just below the upper epidermis. The cells are radially elongated with numerous chloroplasts. These cells remain in 2 to 3 layers.

Spongy parenchyma: Spongy parenchyma is located between palisade parenchyma and lower epidermis. The cells are irregular and loosely arranged. They have fewer chloroplasts than in palisade parenchyma. They have large intercellular spaces, called air chambers. Some air chambers open into substomatal cavities. They perform photosynthesis.

3. Vascular bundles 

Vascular bundles are present in the mid rib and major veins. Each vascular bundle is made of xylem and phloem. The xylem is towards the upper epidermis (adaxial side) and the phloem towards lower epidermis (abaxial side). Each vein has a single vascular bundle. The vascular bundle is conjoint, collateral, and closed type. The bundle sheath surrounds each vascular bundle.

Xylem: Xylem consists of tracheary elements. Protoxylem lies towards upper epidermis and the metaxylem towards the lower epidermis.

Phloem: Phloem lies below xylem. It consists of sieve tubes and the companion cells.

Figure 16 T. S. of Dorsiventral leaf
Image source: MBC Biology