engleski

Gibberellins in flowers and fruit of the Christmas rose (Helleborus niger L.)

The perianth of the Christmas rose, which is white or pink at anthesis, attains photosynthetic capacity during seed development. Surgical experiments, combined with hormone treatments, indicated a role for cytokinins (Tarkowski et al., JXB 57, 2237, 2006) and gibberellins in this process. GC-MS-SIM analysis of fruit extracts suggested the presence of GA1 and GA4, supplemented by minor amounts of GA3 and GA7. GA1 peaked twice: at late anthesis (17 ng/g FW) and shortly before seed ripening (18 ng/g FW), GA4 levels decreased from early anthesis (40 ng/g FW) toward seed ripening (25 ng/g FW), with a minor secondary peak (35 ng/g FW) when seed development was initiated. In the perianth, only GA1 (0.2 ng/g FW at fully established photosynthetic capacity) was so far detected. These data demonstrate that the developing fruit have the capacity to supply GAs to the perianth, as one of the signals that induce and maintain photosynthetic activity. The high overall gibberellin levels in fruit shortly before seed ripening may also be correlated to embryo development which only proceeds to an early cotyledonary stage while the seeds are attached to the mother plant. Supported by grants no. 138166 (National Sciences and Engineering and Research Council of Canada) to J.A.O. and 098-0982913-2829 (Croatian Ministry of Science, Education and Sports) to B.S.

Helleborus niger L.; Christmas rose; Ranunculaceae; fruit and seed development; perianth greening; gibberellin; GA1; GA3; GA4; GA7

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