Question

Describe the internal structure of a dorsiventral leaf with the help of labelled diagrams.

Answer 1

Hint:The leaves of monocotyledonous plants and dicotyledonous plants show a big difference in structure. Monocot leaves are called isobilateral while dicot leaves are said to be dorsiventral in orientation.

Complete answer:
 Dorsiventral leaves are leaves which have a distinct difference between the dorsal (upper) and ventral (lower) surfaces. At first glance a distinct difference between the intensity of green is noticed, with the ventral surface being lighter in colour. The veins of the leaf are also arranged in a reticulate or branched pattern.

Internal structure of the leaves shows three types of tissues: the epidermis, mesophyll, and vascular tissues. The epidermis of the leaves is found on both surfaces. They are hypostomatic, with most stomata being on the lower (abaxial) side of the leaf, and are irregularly arranged. The guard cells are kidney-shaped. It is also covered with a thick cuticle, and unlike monocots, there are no bulliform cells.
In the mesophyll, there are distinct palisade and spongy tissues. In the spongy parenchyma, the tissues are loosely arranged, and are made up of oval cells. While the palisade cells are tall and arranged together in a compact fashion.

The vascular tissue has bundle sheath cells surrounding the bundles. These lack chloroplast. And clear protoxylem elements are not seen.

Note:While dicot leaves have a distinct adaxial and abaxial surface, the monocot leaves are similar in appearance on both sides. Easy to distinguish from dicot leaves due to the parallel venation and absence of a midrib. They are also amphistomatic, with stomata on both leaf surfaces.