Vernalization and gibberellin physiology of winter canola

xii, 138 leaves : ill., ports. ; 28 cm.Winter canola (Brassica napus cv. Crystal) requires vernalization, exposure to chilling, to induce bolting and flowering. Since gibberellins (GAs) have been implicated in the regulation of stem elongation and reproductive development in numerous plants, the role of GAs in events induced by vernalization was investigated. Three classical approaches for studying GA physiology were taken. Plant growth regulators were applied and showed that: (i) GA application induced stem elongation but not flowering in nonvernalized plants and (ii) plant growth retardants that block GA biosynthesis prevented elongation and flowering in vernalized plants. Endogenous GAs were extracted from vernalized and nonvernalized shoot tips, chromatographically purified and quantified by gas chromatography-selected ion monitoring. GA1,3,8,19 and 20 concentrations were higher in the vernalized shoots following vernalization. Feeds of [3H]GA20 to vernalized and nonvernalized plants demonstrated higher rates of [3H]GA1 formation after vernalization, suggesting increased metabolism to the biologically active form. Collectively, these studies indicate a regulatory role of GAs in the control of stem elongation in winter canola, but the role of GAs in flowering was less clear. Vernalization apparently induces stem elongation by increasing GA synthesis and particularly the biosynthesis of GA1