J.C. REVY, ISM / SCIENCE PHOTO LIBRARY J.C. REVY, ISM / SCIENCE PHOTO LIBRARY
Aristolochia stem. Light micrograph of a cross- section through the stem of Aristolochia sp. (family: Aristolochiaceae). This is a typical dicotyledonous stem of a climbing plant. The outer cortex (grey) is strengthened with thick-walled collenchyma cells; the inner cortex consists of parenchyma (yellow) cells. At middle is the vascular stele surrounded by a ring (grey) of supporting sclerenchyma cells. Within the stele are 11 vascular bundles, containing phloem (black semi-circles) and xylem vessels (large hollow black cells bordering the phloem). Phloem conducts plant nutrients; xylem transports water. There is a central pith. Magnification: x7 at 35mm size.
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