RICHARD KIRBY, DAVID SPEARS LTD / SCIENCE PHOTO LIBRARY RICHARD KIRBY, DAVID SPEARS LTD / SCIENCE PHOTO LIBRARY
Light micrograph of a transverse section through the stem of a Jerusalem artichoke, Helianthus tuberosus, a close relative of the sunflower (Helianthus annuus). The large blue area, occupying the centre of the stem, is a region of medullary parenchyma tissue known as the pith. Surrounding this is a ring of pink vascular bundles. Each bundle is composed of three distinct regions: the innermost region (pink with finger- like projections) is xylem tissue, the dark central region is phloem tissue and the deep pink outer region is known as a pericyclic fibre. Magnification: x4 at 35mm size.
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