DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Sunflower root. Polarised light micrograph of a transverse section through the root of a sunflower (Helianthus annuus) plant. The large vessels at centre are xylem cells, which transport water, surrounded by cambium cells. Outside of this are phloem cells, which transport carbohydrates around the plant. The outermost layer is cork cambium. Magnification: x100 when printed at 10 centimetres wide.
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