VERNALIZATION AND GIBBERELLIN PHYSIOLOGY OF WINTER CANOLA - ENDOGENOUS GIBBERELLIN (GA) CONTENT AND METABOLISM OF [H-3]GA(1) AND [H-3]GA(20)

摘要

Winter canola (Brassica napus cv Crystal) is an oilseed crop that requires vernalization (chilling treatment) for the induction of stem elongation and flowering. To investigate the role of gibberellins (GAs) in vernalization-induced events, endogenous GA content and the metabolism of [H-3]GAs were examined in 10-week vernalized and nonvernalized plants. Shoot tips were harvested 0, 8, and 18 d postvernalization (DPV), and GAs were purified and quantified using H-2(2)-internal standards and gas chromatography-selected ion monitoring. Concentrations of GA(1), GA(3), GA(8), GA(19), and GA(20) were 3.1-, 2.3-, 7.8-, 12.0-, and 24.5-fold higher, respectively, in the vernalized plants at the end of the vernalization treatment (O DPV) relative to the nonvernalized plants. Thermoregulation apparently occurs prior to GA(19) biosynthesis, since vernalization elevated the concentration of all of the monitored GAs. [H-3]GA(20) or [H-3]GA(1) was applied to the shoot tips of vernalized and nonvernalized plants, and after 24 h, plants were harvested at 6, 12, and 15 DPV. Following high-performance liquid chromatography analyses, vernalized plants showed increased conversion of [H-3]GA(20) to a [H-3]GA(1)-like metabolite and reduced conversion of [H-3]GA(1) or [H-3]CA(20) to polar H-3-metabolites, putative glucosyl conjugates. These results demonstrate that vernalization influences GA content and GA metabolism, with GAs serving as probable regulatory intermediaries between chilling treatment and subsequent stem growth. [References: 36]