Bamboo stem. Coloured scanning electron micrograph (SEM) of a section through a bamboo stem. The grey tissue is the vascular bundle. The larger cells form the xylem, which transports water and mineral nutrients from the roots throughout the plant. The smaller cells form the phloem, which transports carbohydrates and plant hormones around the plant. Yellow fibres are woody supportive tissue. Bamboos are tropical and subtropical members of the grass family Gramineae. The stems, known as canes or culms, can reach great heights. They are widely used in construction, as these fibres form very tough structures, but are also flexible. Magnification: x90 when printed at 10 centimetres wide.