Question
Describe the structure of an isobilateral leaf. Differentiate between a moncot and dicot leaf.

Answer

Isobilateral (Monocotyledonous) Leaf:

Structure:

  • Epidermis is composed of single layer of cells.
  • Stomata are present on both surfaces of leaf.
  • Mesophyll is not differentiaited into palisade and spongy parenchyma.
  • In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells. These are called bulliform cells. When the bulliform cells in the leaves have absorbed water and are turgid, the leaf surface is exposed. When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss.
  • The parallel venation in monocot leaves is reflected in the near similar sizes of vascular bundles (except in main veins) as seen in vertical sections of the leaves.

Differences between Dicot and Monocot Leaf:

S.No.
Dicot Leaf
Monocot Leaf
i.
Stomata on ventral surface.
Stomata on both surfaces.
ii.
Mesophyll differentiated in Pallisade and spongy parenchyma.
Mesophyll is not differentiated.
iii.
Bulliform cells absent.
Bulliform cells present.
iv.
Vascular bundles are of different sizes.
Vascular bundles are of similar sizes (except in main veins)

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