Nasturtium leaf. Coloured scanning electron micrograph (SEM) of the underside of a nasturtium leaf (Tropaeolum sp.). Numerous hairs (trichomes) cover the surface, they protect the plant from small herbivores and reduce the amount of evaporation from the leaf's surface. The branching veins are also seen. The veins consist of the phloem, which transports sugar made in the leaves during photosynthesis to the rest of the plant, and the xylem, which transports water and minerals from the roots to the leaves.