Peruvian Lily (Alstroemeira sp.) leaves. As the leaves of the Peruvian Lily grow, they twist so that the bottom surface of the leaf is facing upwards. It may be that the twists prevent water from collecting on the leaf and thus reduces the risk of fungal infections. Another theory is that since a leaf has more stomas (respiration pores) on its bottom surface, by twisting the leaf around, the plant can respire more effectively.