Final answer:
Monocot leaves have parallel venation and a uniform mesophyll structure, while dicot leaves have reticulate venation and a differentiated mesophyll structure.
Step-by-step explanation:
Monocot and dicot leaves differ in their mesophyll region in relation to the photosynthetic mechanism. Monocot leaves typically have parallel venation, meaning that the veins run parallel to each other. On the other hand, dicot leaves have reticulate or net-like venation, where the veins run at various angles and do not parallel with each other.
In the mesophyll region, monocot leaves have a uniform arrangement of cells, both in the upper palisade mesophyll and the lower spongy mesophyll, with smaller air spaces between the cells. Dicot leaves, however, have a differentiated mesophyll region where the upper palisade mesophyll is tightly packed with column-shaped cells, while the lower spongy mesophyll has loosely arranged irregular-shaped cells with larger air spaces between them.