Sage leaf midrib. Coloured scanning electron micrograph (SEM) of a section through the midrib of a sage leaf (Salvia officinalis). At centre is the vascular bundle, which consists of xylem (pink) and phloem (yellow) tissues. Xylem transports water and mineral nutrients from the roots throughout the plant and phloem transports carbohydrate and hormones around the plant. The surface of the leaf is covered in many hairs (green) that protect the leaf from predators and help to prevent water loss.