The role of gibberellins in embryo axis development

Abstract

The role of gibberellins (GAs) during early embryo development was examined using microsporederived embryos (MDEs) of Brassica napus. At the globular stage of development, 10 d after initial culture (DAC) when endogenous GA1 levels are increasing rapidly, a triazole, uniconazole, was used at 1, 33 and 100 μM to inhibit GA biosynthesis. Within this dose range there was no apparent effect of the inhibitor on embryo growth through to the early torpedo stage. However, by 25 DAC uniconazole-treated MDEs showed significantly reduced (50%) axis elongation. Addition of GA1 at 33 μM on 14 DAC to embryos pretreated with 1 μM uniconazole on 10 DAC prevented this reduction in axis length, giving axis elongation equivalent to untreated MDEs. Application of GA1 alone, however, did not significantly increase axis elongation. The reduced axis growth seen with uniconazole treatment was due to reduced cell elongation, but not cell number, and the co-applied GA1 thus prevented the uniconazoleinduced reduction in cell length. The elongating axis of MDEs may thus be a useful tool for examining the role of GAs in cell elongation.