QS Study

The anatomical structure of a dicot leaf / dorsiventral leaf. The following arrangement of tissues are seen in the cross-section of a dorsiventral leaf

  1. Upper epidermis
  2. Mesophyll tissue
  3. Vascular tissue
  4. Lower epidermis

(1) Upper epidermis:

(i) It is composed of one layer of compactly arranged parenchymatous cells.

(ii) A thick cuticle layer is present on the upper epidermis.

(iii) Chlorophyll and stomata are absent in this layer.

Functions: i) It protects the inner tissues. ii) Saves the inner use of water.

(2) Mesophyll tissue: Ail the tissues in between upper and lower epidermis except for veins and the branches of vins are called mesophyll tissue.

It has two types of tissues

(a) Palisade parenchyma

(b) Spongy parenchyma

Palisade parenchyma: Below upper epidermis 2-3 rows of long parenchymatous cells are present which is enriched with plenty of chlorophyll.

Function: To prepare food


Spongy parenchyma:

  • The round or oval-shaped cells, situated below the palisade parenchyma, which are arranged scatteredly are said to be spongy parenchyma
  • Within the cells, great deals of inter-cellular spaces are present.
  • A little chloroplast is present m these cells

Functions: i) To contain oxygen; ii) To prepare food.

(3) Vascular bundle:

(i) Veins and their branches make the vascular bundles.

(ii) Vascular bundles consist of xylem and phloem and they are the conjoint, collateral and closed type.

(iii) Vascular bundles are surrounded by one layer of parenchymatous cells called bundle sheath.

Functions: To conduct water and prepared food materials.

(4) Lower epidermis:

(i) It is composed of one layer of compactly arranged parenchymatous cells.

(ii) It contains a thin cuticle layer around this laser

Functions: (i) To protect the inner tissues (ii) Takes part in transpiration and gaseous exchange.