How does the environment influence a leaf's shape and stucture?

Question

How does the environment influence a leaf's shape and stucture?

Answer 1

The drier, hotter, and sunnier a given habitat, the smaller the leaves will be (a common example is Sagebrush or Artemisia tridentata, and cactus is the extreme).  It's also likely the leaves will be coated with a cuticle, whether waxy or mealy, in order to slow the transpiration rate (passage of water out the leaves). There may also be aromatic substances present ("oils"), which serve a similar function.

Conversely, in a rainforest, especially in the understory, the leaves can become huge (Monstera deliciosa, anyone?) and a lot of them are acuminate.  This means they come to a point at the tip so as to shed water.  When there are cuticles, these are usually waxy.  Both the drip tips and the cuticle help prevent fungi, etc., from growing on the leaves.