DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
She-oak stem. Light micrograph of a transverse section through the stem of the Australian she-oak (Casuarina equisetifolia). The she-oak is a drought plant (xerophyte). Xerophytes have evolved an anatomy that cuts down water loss through transpiration. This stem has deep narrow furrows (outer cuttings), and whorls of scale leaves (outer edge) to reduce the area for water loss. The epidermis (outer layer) has thick-walled cells covered in a thick cuticle, and a v-shaped hypodermis of sclerenchyma cells and fibres (yellow-brown).There are three layers of palisade cells (long pink cells) and the vascular bundles (yellow-brown) can be seen at centre. Magnification: x103 when printed 10 centimetres wide.
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