Reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), can promote seed germination in a number of species but their role in soybean has not been fully determined. Ishibashi et al. use the anti-oxidant N-acetylcysteine to counteract the effects of ROS in germinating seeds of soybean, Glcine max, and study endogenous ethylene content, the number and area of cells in the root tip, and the expression of genes related to ethylene biosynthesis. They find that H2O2 promotes germination and N-acetylcysteine suppresses it, and this latter effect is associated with suppressed expression of genes related to ethylene biosynthesis. They conclude that ROS produced in the embryonic axis after imbibition induces the production of endogenous ethylene, which promotes cell elongation in the root tip.