Plants that live on the floor of forests tend to have much larger leaves than plants that live in hot, sunny conditions. offer an explanation for this in which you refer to specific parts of the internal structure of a leaf

The reason that plants tend to have larger leaves on the forest floor is because the leaves need to capture more sun.

By increasing the surface area of the leaf, which also increases the amount of sun it collects, it can compete with the larger trees and vines when it is exposed to less sun due to said trees.