DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Cucumber stem. Light micrograph of a cross-section through part of a vascular bundle from a cucumber (Cucurbita sp.). This vascular bundle is from the stem of the cucumber. The large white spaces are xylem vessels; the smaller blue and white ones are phloem. Cambium tissue is also seen. The blue structures in the phloem layer are the sieve cells. The holes in the sieve cells allow cytoplasmic continuity between adjacent sieve cells. Cytoplasm is the fluid contents of a cell, normally retained inside a cell, but here moving between cells through the holes in the sieve cells. The phloem passes nutrients around a plant. The xylem vessels pass water around a plant. Magnification: x22 when printed 10cm wide.
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