Responsivencess of Intact and Scarified Seeds of Barbarea vulgaris to Gibberellic Acid and Changes in Phytochrome

Either red light or millimolar levels of gibberellic acid promoted germination of seeds of yellow rocket (Barbarea vulgaris R. Br.), and their effects were generally additive. Buffering the substrate pH at 3.0, addition of 20 mM nitrate to the substrate, preliminary incubation at 10 or 30°C, and brief scarification of the seeds increased responsiveness of the seeds to gibberellic acid. Scarification increased several thousandfold the sensitivity of the seeds to gibberellic acid. Pretreatment of the seeds in darkness or far-red light did not lower their responsiveness to gibberellic acid. These results suggest that uptake of gibberellic acid is a limiting factor in the stimulation of germination in intact seeds and that there is only a minimal requirement for active phytochrome to express gibberellic acid action.