Profile of Plant Hormones and their Metabolites in Germinated and Ungerminated Canola ( Brassica napus ) Seeds Imbibed at 8°C in either GA 4+7 , ABA, or a Saline Solution

Abscisic acid (ABA) and gibberellins (GAs) are two major phytohormones that regulate seed germination in response to internal and external factors. In this study we used HPLC-ESI/MS/MS to investigate hormone profiles in canola ( Brassica napus ) seeds that were 25, 50, and 75% germinated and their ungerminated counterparts imbibed at 8°C in either water, 25 μM GA 4+7 , a 80 mM saline solution, or 50 μM ABA, respectively. During germination, ABA levels declined while GA 4 levels increased. Higher ABA levels appeared in ungerminated seeds compared to germinated seeds. GA 4 levels were lower in seeds imbibed in the saline solution compared to seeds imbibed in water. Ungerminated seeds imbibed in ABA had lower GA 4 levels compared to ungerminated seeds imbibed in water; however, the levels of GA 4 were similar for germinated seeds imbibed in either water or ABA. The ABA metabolites PA and DPA increased in seeds imbibed in either water, the saline solution, or ABA, but decreased in GA 4+7 -imbibed seeds. In addition, ABA inhibited GA 4 accumulation, whereas GA had no effect on ABA accumulation but altered the ABA catabolism pathway. Information from our studies strongly supports the concept that the balance of ABA and GA is a major factor controlling germination.