DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Grapevine stem. Light micrograph of a section through the one-year-old stem of a grapevine (Vitis rotundifolia), showing secondary thickening. The outer cortex (turquoise) has produced a phellogen (cork cambium) and six files of phellem cells (cork, brown), and the epidermis will be shed. Below the inner cortex (turquoise) is the vascular ring; the first layer is a ring of fibres (brown); the next ring is the phloem (dark blue) with sieve tubes; next is the cambium (light blue cells). The wood under the cambium has one ring of large vessels (blue circles), while the rest of the wood is made up of smaller vessels - tracheids and wood parenchyma. The radial lines between the wood and phloem are medullary rays (blue). The central pith is full of parenchyma.
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