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 leaf	Monocot 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.