Introduction Monocot leaves are the leaves that appear on plants produced from seeds with single cotyledon like Maize, Rice, Grass, Wheat, etc. Monocot leaves are said to be isobilateral leaves as both the surface of the leaves are with the same coloration. The leaves are usually ribboned like with parallel venation. Parallel venation means veins in the leaf are arranged in a parallel fashion. We are studying the anatomy of the leaf means, we are studying the internal structure or arrangement of various tissues arranged internally in the leaf. The various tissues present inside the leaf will carry out some specific functional activities for the leaf. By mounting a thin section of a monocot leaf like that of a grass leaf or maize leaf on a clean glass slide and after staining can be observed under a Compound microscope, we can get a clear view of the arrangement of its various tissues in an orderly fashion.
Internal organization of various tissues in monocot leaf The following are the various tissues and their functional activities of monocot leaf:-
In a monocot leaf, an equal number of stomata are present on both the surfaces of the epidermis. Such a condition is usually described as Amphi stomatic condition. A few cells present in the upper epidermis are enlarged to form motor cells called bulliform cells. These cells are larger when compared to other epidermal cells. These cells will be helpful for the monocot leaves to roll over themselves to reduce the surface area exposed to sunlight and become shrunken during hot midday time to reduce the rate of transpiration. It is an adaptation for monocot leaves to check the loss of water from their surface during the hot summertime.
In both upper and lower epidermal layers of monocot leaf, an equal number of stomata are present. But in dicot leaves, more stomata are present in the upper epidermal layer and fewer stomata in the lower epidermal layer. In the case of monocot leaf, the two guard cells which form the stoma are dum-bell shaped. But the two guard cells which form stoma in dicot leaves are kidney or bean-shaped.
Phloem tissue in the vascular bundle is present towards the lower epidermal surface of the leaf. Phloem is a complex permanent tissue made of sieve tubes and sieve pores, companion cells, phloem parenchyma, and phloem fibers. Phloem tissue in a leaf is concerned with the conduction of dissolved food materials (usually glucose).
Vascular bundles in monocot leaf are described as conjoint, collateral, and closed with endarch xylem. As xylem and phloem are present on the same radius, the vascular bundle is described as conjoint and collateral. The vascular bundle is described as closed as there is no cambium present between xylem and phloem. Xylem vessels are of two types-protoxylem and metaxylem vessels. Protoxylem vessels are newly formed young vessels while metaxylem vessels old and well-matured vessels. Xylem bundles are described here as endarch because the protoxylem vessels face towards the upper epidermis. Vascular bundles help in the transport of water, dissolved minerals, and dissolved food materials in the leaf. Vascular bundles also provide strength to the leaf.
Most frequently asked questions:-
Ans. Bulliform cells are large bubble-shaped epidermal cells present in groups on the upper surface of monocot leaves. These cells help in the roling of leaves to reduce the loss of water during hot midday times.
Ans. The guard cells of stoma are kidney or bean-shaped in dicot leaves and dumbel-shaped in monocot leaves.
Ans. The veins of leaves represent vascular bundles that include xylem and phloem tissues.
Ans. Mesophyll tissue is differentiated into palisade and spongy parenchyma in dicot leaves while the mesophyll is undifferentiated and contain only spongy parenchyma in monocot leaves.
The guard cells in dicot leaf are kidney-shaped while monocot leaf are dumbel-shaped.
Ans. In dicot leaf reticulate venation and in monocot leaf parallel venation.
Ans. Mesophyll tissue contain chloroplasts and chlorophyll and this tissue help in photosynthesis to prepare carbohydrate food.
Ans. The cavities present above the stomata on the lower epidermis of a leaf are known as sub-stomatal chambers. They store CO2 or water vapor in these cavities till they diffuse.
Ans. The thick cells present around the vascular bundles that include starch granules in monocot leaf is known as bundle-sheath or starch-sheath.
Here is a video of the anatomy and internal structure of a Monocot leaf:-