DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Sunflower stem. Light micrograph of a transverse section through the stem of a sunflower (Helianthus annuus) plant. A line of vascular bundles is seen across centre. Each bundle contains phloem (blue and brown) and xylem (red and yellow) cells, which transport carbohydrates and water around the plant respectively. Magnification: x45 when printed at 10 centimetres wide.
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