HELP! Leaf Structures??????

My guess on the two structures that conserve water would be the stomata and the cuticle. The stomata open and close due to varying conditions. When closed photosynthesis is essentially shut down. But water loss is decreased. The cuticle is a waxy layer on the surface of leave that prevents from evaporating to the air. Some leaves have thicker cuticles than others. There are other adaptations that can prevent water loss. One of these are dermal hairs that grow on the surface of leave to reduce air movement across the leaf surface. This can reduce water loss as well. But I would definitely go for the first two: stomata and cuticle.