POWER AND SYRED / SCIENCE PHOTO LIBRARY POWER AND SYRED / SCIENCE PHOTO LIBRARY
Buttercup stem. Coloured scanning electron micrograph (SEM) of a section through the stem of a buttercup (Ranunculus sp.) plant. At centre right is a spiral of lignin, a woody substance that wraps around a xylem vessel to strengthen it. Xylem vessels transport water and mineral nutrients around the plant.
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