Abstract
Seed germination, a crucial stage in a plant's life, is complicated by several factors, including plant hormones and environmental factors. Plant hormones such as gibberellins (GAs), abscisic acid (ABA), brassinosteroid and ethylene play key roles in seed germination. Reactive oxygen species (ROS) promote germination of seeds in several plant species. In contrast, antioxidants suppress the effect of ROS on seed germination. However, the mechanism underlying ROS-induced germination of seed has not been clarified. We therefore focus on relationships between ROS and plant hormones signaling in seed germination. After imbibition, ROS were produced in embryo and aleurone cells of barley seed and in embryonic axis of soybean seed. ROS produced in embryo of barley seed and embryonic axis of soybean seed regulated GA and ethylene biosynthesis, respectively. In aleurone cells of barley seed, ROS were produced by GA and were suppressed by ABA. ROS produced by GA in aleurone cells negatively regulate ABA signals and consequently promote production of a-amylase that acts as key enzyme in seed germination. Taken together, ROS produced after imbibition is likely to be involved in seed germination through the regulation of plant hormone biosynthesis and signaling.
