engleski

Bioactive gibberellins in carpels and fruit of the Christmas rose (Helleborus niger L.)

In Christmas rose (Helleborus niger L.) flowers, the initially white or rose perianth turns green after fertilization, a process which depends on the presence of developing fruit, or, in their absence, can be induced by application of gibberellins. In the present study, developing pistils and fruit were analyzed for the presence of the common bioactive gibberellins, GA1, GA3, GA4, and GA7. Extracts of freeze-dried plant material, prepared in the presence of deuterium-labeled internal standards, were passed through a series of purification and derivatization steps (solvent partition, solid-phase extraction, HPLC, preparation of GA methyl ester-trimethylsilyl ethers) and analyzed by gas chromatography-mass spectrometry-selected ion monitoring. Kováts retention indices and the presence of the respective molecular ions and two characteristic fragment ions suggested the presence of all four gibberellins. GA4 was most abundant, followed by GA1, while GA3 and GA7 were of minor significance. The overall pool size for these four gibberellins in the fruit started to increase markedly when chlorophyll formation in the perianth was initiated, suggesting a role for fruit-derived gibberellins in the induction and maintenance of photosynthetic capacity in the perianth. GA4 concentrations peaked during early anthesis and embryo initiation, and decreased slightly thereafter, possibly because embryo development continued to the initial cotyledonary stage by the time seeds were shed. GA1 levels peaked after pollination, decreased during embryo initiation, and rose again as the fruit approached maturity. These data identify GA1 and GA4 as major gibberellins in Christmas rose fruit and suggest a role for gibberellins in specific stages of development.

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

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