Barnyard Grass Stress Triggers Changes in Root Traits and Phytohormone Levels in Allelopathic and Non-Allelopathic Rice

Despite the growing knowledge concerning allelopathic interference with barnyard grass, little is understood regarding the competitive physiological mechanisms of the interaction between allelopathic rice and herbicide-resistant barnyard grass. A hydroponic system was employed to investigate the root morphological traits and different phytohormonal changes in allelopathic and non-allelopathic rice cultivars when co-planted with quinclorac-resistant and -susceptible barnyard grass, respectively. The results show that shoot and root biomass were greater in PI. Barnyard grass stress induced an increase in shoot and root biomass in PI at 7 and 14 days of co-culturing rice and barnyard grass. Especially under the stress of quinclorac-resistant barnyard grass, the shoot biomass of PI increased by 23% and 68%, respectively, and the root biomass increased by 37% and 34%, respectively. In terms of root morphology, PI exhibited a significantly higher fine-root length, in root diameters of <0.5 mm, a greater number of root tips, and longer root tips compared to LE. The response to quinclorac-resistant barnyard grass stress was consistent in terms of the SA and JA content. The obvious accumulation of SA and JA was observed in two rice cultivars under quinclorac-resistant barnyard grass stress, with greater amounts of SA and JA in PI. The significant decrease in auxin (IAA) and abscisic acid (ABA) content in rice was detected from 7 to 14 days under co-culture stress. Additionally, highly significant and positive correlations were found between SA and JA content, and the number of root tips and root tip length at root diameters of 0-0.5 mm in rice.

Automated summary

This study investigated the root morphological traits and changes in phytohormones of allelopathic and non-allelopathic rice cultivars when co-planted with herbicide-resistant barnyard grass. The results showed that the allelopathic rice had greater shoot and root biomass and exhibited better root morphology compared to other rice cultivars. Additionally, the allelopathic rice responded positively to the stress of herbicide-resistant barnyard grass, with changes in phytohormonal content.