Different Responses of Invasive Weed Alternanthera philoxeroides and Oryza sativa to Plant Growth Regulators

Invasive plants cause a global loss of biodiversity, pose a major threat to the environment and economy, and also significantly affect agricultural production and food security. Plant growth regulators (PGRs) are widely used in agricultural production and might also affect invasive weeds distributed around crops in various ways. At present, there are few studies concerning whether there are significant effects of PGRs on invasive weeds. In this study, two widely used PGRs in paddy fields, gibberellic acid (GA) and paclobutrazol (PAC), were applied on Oryza sativa and a noxious weed Alternanthera philoxeroides, which is frequently distributed in paddy fields. The purpose of this study was to investigate if there are different responses of rice and weeds to these two plant regulators and the significant effects of PGRs on invasive weeds. The results showed that GA significantly promotes the total biomass of A. philoxeroides by 52.00%, but does not significantly affect that of O. sativa. GA significantly increases the growth of aboveground and belowground A. philoxeroides, but not that of O. sativa. On the other hand, PAC extremely inhibited the aboveground and belowground biomass of A. philoxeroides by more than 90%, but did not significantly inhibit the belowground biomass of O. sativa. PAC also enhanced the leaf nitrogen content and chlorophyll content of A. philoxeroides, but not the traits of O. sativa. Therefore, the effects of PGRs are significantly different between rice and the invasive weed. The potential promotion effects of PGRs on weeds that are frequently distributed in farmland warrant sufficient attention. This is probably one of the important reasons why invasive weeds can successfully invade the agricultural ecosystem with large human disturbance. This study might sound an alarm for weed control in paddy fields.