Role of nano-Biochar in attenuating allelopathic effect from Imperata cylindrica on rice seedlings
It is reported that Imperata cylindrica, a successful invasive plant in North America, has covered many parts of the United States, especially the southeastern region which is the main rice growing region. The invasion of I. cylindrica could threaten rice production. In this study, we hypothesize that biochar nanoparticles (nano-BC) can reduce the stress from the root exudates of I. cylindrica. Ferulic acid (FA) is a major chemical of I. cylindrica root exudates, and we selected its analog, salicylic acid, as an experimental control. We found that nano-BC has detoxification effects for rice seedlings under FA treatments. Rice seedlings grow better and the phenotype of rice seedlings recovers after nano-BC application under FA treatments. In comparison to the seedlings treated with FA, the biomass of the seedlings increases 344% and 435% after adding 200 mg kg-1 and 400 mg kg-1 of nano-BC to the FA treatment in the pot experiment, respectively. Superoxide dismutase activities (antioxidant system index) and malondialdehyde concentration (lipid peroxidation marker) decline after the addition of nano-BC. Additionally, the rice growth is better after the addition of nano-BC in the FA treatment. Total chlorophyll concentration displays a recovery trend, and the recovery rates are 55% and 96% after 400 mg L-1 and 400 mg kg-1 of nano-BC are added to the FA treatments in the hydroponic and pot experiments, respectively. The expression of three salicylic acid-related genes also demonstrates recovery in the treatment with nano-BC and FA. Therefore, nano-BC is a potential material that can be used to protect rice production from the stress of I. cylindrica invasion.