Studies in seed dormancy

Summary

The three major fractions (II, III and V) of the five fractions of gibberellin (GA)-like activity obtained by the thin layer chromatographic purification of an extract of hazel embryos have been examined by gas liquid chromatography and combined gas chromatography-mass spectrometry. By these techniques GA₁ was identified as the methyl ester trimethylsilyl ether in fraction II and GA₉ as the methyl ester in fraction V. Both substances were clearly separated from other components by gas liquid chromatography so that accurate determination of their concentrations was possible. GA₁ accounted for most of the activity found by bioassay in fraction II while GA₉ accounted for only part of the activity of fraction V. The GA-like substances in the less biologically active thin layer chromatography fractions have not yet been identified.

Freshly harvested seeds contained GA₁ but GA₉ was not detected. After 28 days dry storage and 42 days imbibition and chilling at 5°, the GA₁ content was very low and GA₉ was still below the limits of detection. On subsequent exposure of the seeds to a temperature of 20° for 8 days, there was a 40-fold increase of GA₁ and at least a 300-fold increase of GA₉.