Role of Endogenous Plant Growth Regulators in Seed Dormancy of Avena fatua

Publisher Website
Google Scholar
Abstract
GA1 was identified by combined gas chromatography-mass spectrometry as the major biologically active GA in seeds of wild oat (Avena fatua L.) regardless of the depth of dormancy or stage of imbibition. Both unimbibed dormant and nondormant seeds contained similar amounts of GA1 as estimated by the d5-maize bioassay. During imbibition, the level of GA1 declined in both dormant and nondormant seeds, although the decline was more rapid in dormant seeds. Only in imbibing nondormant seeds did the GA biosynthesis inhibitor, 2-chloroethyltrimethylammonium chloride (CCC), cause a reduction in the level of GA1 from that observed in control seeds. While afterripening does not cause a direct change in the levels of GA during dry storage, it does induce a greater capacity for GA biosynthesis during imbibition. Nondormant seeds imbibed in the presence of 50 mM CCC germinated equally as well as untreated seeds. When wild oat plants were fed CCC throughout the entire life cycle, viable seeds were produced that lacked detectable GA-like substances. These seeds afterripened at a slightly slower rate than the controls. Moreover, completely afterripened (nondormant) seeds from plants fed CCC continuously contained no detectable GA-like substances, and when these seeds germinated, dwarf seedlings were produced, indicating GA biosynthesis was inhibited during and after germination. The increased capacity for GA biosynthesis observed in imbibing nondormant seeds is not a necessary prerequisite for germination. GA biosynthesis in imbibing nondormant seeds is one of many coordinated biochemical events that occur during germination rather than an initiator of the processes leading to germination.