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John Ray in the year 1682 published the classification of flowering plants or angiosperms into two major groups. Later a botanist named Antoine Laurent de Jussieu in 1789, replaced the earlier classifications by a new one. According to which classification of flowering plants were divided into eight major groups, and the largest number of species belonged to the monocots and dicots. A leaf represents a lateral attachment to the plant stem that supports an important function of photosynthesis. It is a vital structure of the plant in terms of feeding. In botany, the plants are classified on the basis of various aspects. Cotyledon is one such first significant part of the embryo that emerges from the seed and is formed during the process of embryogenesis along with their roots and shoots before germination. When the seed germinates, cotyledon emerges as the first embryonic leaves of a seedling.
Monocot Leaf
A Monocotyledonous leaf is narrow and elongated showing parallel venation, which is mainly used to differentiate monocotyledonous plants from dicots. Monocot leaves are generally isobilateral since both the surfaces of the leaves appear to be similar to the same coloration.
The primordial monocot leaves consist of a proximal leaf base or hypophyll and a distal hyperphyll. The hyperphyll is the dominant portion of the leaf in dicots, whereas in monocots, the hypophyll acts as the dominant structure.
The leaves are narrow and linear with a protective sheath covering the stem at the base, but there are various exceptions within the monocots that might not have similar structures.
The venation, as already mentioned, is of the striate type which is mostly longitudinally striate and often, palmate-striate or pinnate-striate.
The veins present on the leaf surface arise from the base of the leaf and move together to the apex.
Most monocotyledonous plants consist of a single leaf per node since the leaf base occupies more than half of the circumference of the stem of plants.
The emergence of a larger leaf base is mainly attributed to the differences in the development of the stem during zonal differentiation.
Examples of Monocot Leaves
1. Maize leaves
Maize leaves are generally considered the most typical monocot leaves that possess simple and orderly arranged structures.
A typical maize plant comprises about 20 leaves that may be present in different stages of development. A mature maize leaf is about 70 cm long and 8 cm wide.
A maize leaf is further divided into three regions; an upper blade, lower sheath, and auricle. The leaf cells are highly oriented and aligned to form parallel lines and elongated shapes.
The leaf blade of maize leaf possess adaxial and abaxial epidermal tissue that encloses the mesophyll and vascular tissue.
2. Grass leaves
A grass leaf is a monocot leaf with an elongated structure that arises from the node, consisting of a basal cylindrical sheath encircling the stem and other younger leaves.
The sheaths present on the outer surface are hollow cylinders that cut down on one side. These sheaths mainly form overlapping structures.
The leaf possesses an auricle that may exist either as an ear-like projection or can be reduced to a hairy edge that is present at the base of the leaf blade.
The epidermis of a grass leaf comprises specialized hair cells that protects the plants against different harmful agents.
Dicot Leaf
Dicotyledonous leaves are mainly rounded possessing reticulate venation that can be differentiated from monocotyledonous leaves based on their structure and anatomy. A typical dicot leaf comprises a lead blade which is also known as the lamina. The lamina represents the widest part of a leaf.
Dicot leaves are usually dorsoventral since the dorsal and ventral parts of the leaves are differentiated based on the coloration of the leaves. The dorsal side of the leaf is usually more pigmented than the ventral side.
Dicot leaves are attached to the stem by the petiole that differentiates them from monocot leaves that are directly attached to the stem.
Small green appendages known as the stipules that might be present at the base of the petiole in some dicot leaves.
Dicot leaves possess a midrib that runs along the leaf blade and travels upto the length of the leaves. Many branches develop on opposite sides of the midrib thus, giving rise to the reticulate venation.
Species depend upon the number of leaves present on a node in the stem but dicots usually possess two or more leaves arising from a single node.
Dicot leaves are further divided into different groups based on the different forms of leaf, as some are simple leaves while others are compound.
Examples of Dicot Leaf
Mustard leaves
It is a typical dicot plant mainly used for studies regarding dicotyledonous plants.
Its leaves begin growing within 4 weeks when the leaves reach 6-8 inches in length.
The leaves are green in colour and broad with reticulate venation. The leaves are usually dorsoventrally flattened, and the ventral surface is lighter than the dorsal surface.
Mint leaves
It is a fast-growing plant consisting of round lanceolate leaves which are arranged in opposing pairs on the stem.
The leaves are generally small in size ranging between 4-5 inches in length. The size of the leaves, moreover, depends on the age of the leaves and their maturity.
The leaves possess reticulate venation along with a central midrib via which branched veins arise.
Functions of Monocot and Dicot Leaf
The functions of leaves are more specifically similar in both dicot and monocot plants. The various functions of leaves depend on the plant species, their environment, and their age. Below discussed are some of the functions of monocot and dicot plants leaves:
One of the important functions of leaves in green plants is the preparation of food by the process of photosynthesis. The cells that are present in the leaves comprises chlorophyll since one-fifth of the cells in the mesophyll consists of chlorophyll-containing chloroplasts. The large and broad surface of the leaves helps in absorption of a larger amount of sunlight which is required for photosynthesis.
The epidermis and cuticle of the leaves prevent excessive loss during transpiration, which protects the plants from drying up.
The leaves are stomata that are a vital structure for the movement of water from the plant into the atmosphere by the transpiration process. This is significant in order to draw water along with minerals from the soil via the roots.
In addition to facilitating transpiration, stomata are also involved in the exchange of gases. The stomata takes in carbon dioxide from the air and gives out oxygen during the process of photosynthesis.
In a few plants like cabbage and lettuce, the food prepared via the cells in the leaves is stored in the leaves in various forms.
Conclusion
Monocot leaves are flowering plants possessing seeds that comprise only one embryonic leaf or cotyledon. Plants are divided mainly into two categories: Monocots and Dicots. Monocot leaves are elongated slender with parallel veins. Whereas, dicot plant leaves possess distributed veins in reticulated patterns. Dicot leaves are generally Hypostomatic. In Monocot leaves, the mesophyll is generally one layered. In Dicots, the flower parts may be pentamerous or tetramerous. So with this we come to an end of this topic. We hope that this article has helped you to clear your concepts regarding monocot and dicot leaves.
