engleski

Cytokinins in fertilised flowers of Helleborus niger L.

The (initially white) perianth of fertilized Christmas rose (Helleborus niger L.) flowers turns green and persists until the seeds are ripe. This process stops when the developing fruit are removed, but is restored by applying cytokinins in lanolin (Salopek-Sondi et al. : J. Plant Physiol. 157, 357, 2000 ; J. Exp. Bot. 53, 1949, 2002), thus suggesting a role for cytokinins in the metamorphosis of fruit-bearing flowers. LC-MS/MS analysis confirmed their presence in both the fruit and the perianth. We identified N^6-isopentenyladenine, zeatin, and dihyrozeatin bases as well as the corresponding 9-ribosides by tandem mass spectroscopy. In order to obtain satisfactory spectral information, the partially purified plant extracts were derivatized before LC-MS/MS. In a separate approach, fractionation by ion exchange and immunoaffinity chromatographies, combined with phosphatase and glucosidase treatments and LC-MS, indicated the additional presence of citokinin ribotides and glucosides in significant quantities. The abundance of cytokinins (in particular, trans-zeatin and derivatives) in the fruit increased enormously during early seed development and remained high until about 2 weeks before fruit ripening. The steep rise in fruit cytokinins coincided with the greening process in the perianth, but the changes in cytokinin levels in the perianth itself were less pronounced.

Helleborus niger; Christmas rose; cytokinin; flower and fruit development

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