DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Indian balsam root. Light micrograph of a transverse section through the root of an Indian balsam (Impatiens glandulifera) plant, showing primary succulent tissue. From outer root to centre: single layer of epidermis (red); cortex of parenchyma, with large cells storing water (blue); ring of pericycle (dark-violet). In the centre of the root there is no pith, but xylem, primary metaxylem (large vessels, red) and protoxylem made up of star-shaped arms (small cells, red). Next is the primary phloem, in-between the xylem (small cells, blue), with sieve tubes. Magnification: x37 when printed 10 centimetres wide.
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