Prior hydration of Brassica tournefortii seeds reduces the stimulatory effect of karrikinolide on germination and increases seed sensitivity to abscisic acid

Abstract

Background and Aims: The smoke-derived compound karrikinolide (KAR 1) shows significant potential as a trigger for the synchronous germination of seeds in a variety of plant-management contexts, from weed seeds in paddocks, to native seeds when restoring degraded lands. Understanding how KAR1 interacts with seed physiology is a necessary precursor to the development of the compound as an efficient and effective management tool. This study tested the ability of KAR1 to stimulate germination of seeds of the global agronomic weed Brassica tournefortii, at different hydration states, to gain insight into how the timing of KAR1 applications in the field should be managed relative to rain events. Methods: Seeds of B. tournefortii were brought to five different hydration states [equilibrated at 15 relative humidity (RH), 47 RH, 96 RH, fully imbibed, or re-dried to 15 RH following maximum imbibition] then exposed to 1 nm or 1 µM KAR1 for one of five durations (3 min, 1 h, 24 h, 14 d or no exposure). Key Results: Dry seeds with no history of imbibition were the most sensitive to KAR 1; sensitivity was lower in seeds that were fully imbibed or fully imbibed then re-dried. In addition, reduced sensitivity to KAR1 was associated with an increased sensitivity to exogenously applied abscisic acid (ABA). Conclusions: Seed water content and history of imbibition were found to significantly influence whether seeds germinate in response to KAR1. To optimize the germination response of seeds, KAR1 should be applied to dry seeds, when sensitivity to ABA is minimized. © The Author 2010.