Bamboo stem. Coloured environmental scanning electron micrograph (ESEM) of a section through the stem of a bamboo plant (family Gramineae), showing a vascular bundle. Vascular bundles consists of xylem (larger openings) and phloem vessels (smaller openings). Xylem transports water and mineral nutrients from the roots throughout the plant, while phloem transports carbohydrates and plant hormones around the plant.