Leaves in the rainforests mostly have flat and broad surfaces. This is because in rainforests there are very tall trees which form a canopy on the top. This does not allow the sunlight to reach the forest floor.The small plants that grow on the forest floor have flat and broad leaves so that the little amount of sunlight that enters through the gaps can reach these leaves thus allowing them to perform photosynthesis.
3
Maitreya Pathade answered this
Leaves are broad and flat so that they can absorb large amounts of light energy from the sun. more the surface area exposed to sun light more will be the rate of photosynthesis.