Monocotyledonous leaf

Monocotyledonous leaf (Isobilateral / Equifacial Leaf)

In monocot leaves, the internal structure of both upper and lower leaf surfaces look similar.

Epidermis

  • The epidermis is composed of barrel shaped parenchyma cells.
  • It bears cuticle and epidermal hairs.
  • In grasses, the epidermal cells are impregnated with silica.
  • In these plants, some cells are modified into large, empty, colorless and round shaped cells called bulliform cells or motor cells.
  • These cells contracts during dry season resulting in the curling up of leaves.
  • When the bulliform cells absorb water, they become turgid and leaves are exposed.
  • During try season, these cells become flaccid and cause the leaves to curl up to prevent water loss.
  • Stomata are present in both upper and lower surfaces.

Mesophyll

  • The mesophyll is not differentiated into palisade or spongy layer.
  • It is composed of large spongy cells with chloroplasts.
  • The cells are isodiametric with intercellular spaces.

Vascular Bundles

  • Due to parallel venation, the vascular bundles are of nearly same size in all veins, except in the midrib.
  • The bundles are surrounded by a bundle sheath. It also contains chloroplasts.
  • Xylem is seen on the upper side, and phloem is seen on the lower side.
  • Xylem contains tracheary elements.
  • Phloem consists of sieve tubes and companion cells.

 

Dicot leafMonocot leaf
  • Upper surface is darker than the lower side.
  • Both surfaces are equally green.
  • Epidermis does not contain silica.
  • Epidermis is pregnant with silica.
  • Leaf is hypostomatic – the stomata are seen on the lower epidermis.
  • Leaf is amphistomatic – Stomata are found on both upper and lower sides.
  • Guard cells – Kidney shaped
  • Guard cells – Dumbbell shaped.
  • Bulliform cells – present.
  • Bulliform cells – absent.
  • Mesophyll – Differentiated into palisade and spongy layers.
  • Mesophyll – Undifferentiated.
  • Venation – Reticulate.
  • Venation – Parallel.
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