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Perisperm |
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perisperm [′per·ə‚spərm]
(botany) In a seed, the nutritive tissue that is derived from the nucellus and deposited on the outside of the embryo sac. Perisperm reserve nutritive tissue in a seed used by the embryo in sprouting. Functionally, the perisperm is similar to the endosperm. However, it forms from the nucellus and has a diploid, and not triploid, chromosomal set. In addition, it lacks proteins and contains chiefly starch and, less commonly, fat. Perisperm characterizes plants of the families Caryophyllaceae, and Zingiberaceae, Piperaceae, and Nymphaeaceae. Among gymnosperms, it is found in Gneticae and Taxaceae. The perisperm constitutes all or part of the reserve tissue. When it forms only part of the seed’s reserve, it develops parallel with the endosperm. Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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