Monocot vs Dicot Leaves
A leaf is attached to the stem of a plant at the node. The distance between two adjacent nodes is the inter node. Some leaves are attached to the stem by a stalk or a petiole. Some do not have stalks. Therefore, they are called sessile. In dicot leaves, the petiole continues as the midrib forming a network of veins. This is called reticulate veination. In monocots, a midrib is not prominent mostly, and the type of veination is parallel. The leaf blade is flat and thin. In dicots, it shows various shapes. In monocots, it is mostly linear. The leaf tip, leaf base and the margin also show different variations. At the axil, between the leaf and the stem, is the axillary bud. This may develop in to a branch or a flower in some plants. At the node, there is a structure called stipule. The shape and the size of this stipule may differ in different species.
In dicots, the leaves are attached to the stem in a way, so that light falls mainly on the upper surface. Therefore, there is well marked differentiation of cell layers or tissue layers within the leaf. These leaves are called dorsoventral leaves. The outermost layer on the dorsal and ventral surfaces is the epidermis. It consists of a tightly packed layer of living cells. There are no pigments. So that light can penetrate the epidermal layer. Above the epidermis is the cuticle made up of cutin. On the lower epidermis in dicots, there are large numbers of stomata surrounded by two kidney shaped guard cells with chloroplasts. On the upper epidermis, there may be no stomata or the stomatal density is very low. The palisade layer is below the upper epidermis. It is found arranged lengthwise vertically.
A normal mesophytic leaf has only one layer of palisade cells. These cells are packed with chloroplast. There are several layers of round shape spongy parenchyma cells between the lower epidermis and the palisade cells. They have large intercellular spaces, continuous with the stomatal or respiratory chambers near stomata. They also have chloroplasts. In the midrib region, just below the upper and lower epidermis are several layers of collenchymas. The mid vein and the lateral veins consist of xylem tissues towards the upper epidermis. Towards the lower epidermis are phloem tissues. Lateral veins may be found in spongy parenchyma region. All veins including the mid vein are surrounded by a bundle sheath normally made of parenchyma.
Monocot leaves are described as bicolateral leaves. There is no differentiation of mesophyll cell layers. There are stomata equally distributed on both epidermis. Normally they are attached to the stem, so that light falls equally on both surfaces.
What is the difference between Dicot Leaf and Monocot Leaf?
• Dicot leaves possess reticulate veination and monocot leaves possess parallel veination.
• Dicot leaves are dorsoventral leaves, and monocot leaves are bicolateral leaves.