Endogenous gibberellins and dormancy in beechnuts

Attempts to break dormancy of beechnuts (Fagus sylvatica L.) by soaking them in GA3 and GA4/7 solutions were successfully performed. The ability of these exogenous gibberellins (GAs) to break dormancy suggests a possible role for endogenous GAs in this process. Endogenous GAs were extracted from dormant and non dormant seeds and identified by gas chromatography-mass spectrometry (GC-MS) with full scans. Fourteen GAs were detected: GA1, GA2, GA3, GA4, GA7, GA9, GA15, GA19, GA20, GA29, GA36, GA37, GA51 and GA54. Levels of some endogenous GAs (GA1, GA3, GA8, GA9, GA19 and GA20) from seeds treated with different dormancy breaking treatments were analysed separately in cotyledons and embryonic axis. After purification of the extracts, GAs were quantified by GC-selected ion monitoring (GC-SIM) with deuterated GAs as internal standards. The results showed that GAs corresponding to the 13-OH pathway seemed to be involved in dormancy breaking. Along the process, accumulation of GA3 in the embryonic axis took place at the same time as an increase of GA20 and a decrease of GA19 in the cotyledons. The quantitative differences between dormant and non dormant seeds in some of the analysed GAs and the positive effect of GA applications may suggest that GAs are directly involved in the dormancy breaking process.