Study on allelopathic effect of extract of rice straw on wheat.

An experiment was conducted to study the allelopathic effect of different extract concentrations of water-soaked rice straw on germination rates of wheat seed,seedling height and root length.Results showed that the seed germination rate,seedling height and root length were promoted by the extract at its lower concentrations but inhibited at its higher concentrations.It was found that the higher the concentration,the more severe the allelopathic effect.At the mass concentration of 0.01 g/mL,the extract slightly promoted germination but significantly enhanced seedling height and root length.As the mass concentration was increased to 0.02 g/mL,both seed germination and seedling growth were inhibited.The degree of inhibitory effect from the added rice extract was more severe on seedling growth than on seed germination.At this extract concentration,added growth regulators,gibberellin acid (GA3) superior to added humic acid,could not only overcome the adverse allelopathic effect but also significantly promote seedling growth.As the extract concentration rose to 0.04 g/mL,seed germination and seedling growth were further inhibited.Under such circumstance,neither added GA3 or humic acid was able to overcome the adverse allelopathic effect from the rice extract.