| In this research, broccoli was employed as the experimental material by combining field and laboratory analyses to have studied the effects of 0.15 mmol·L-1 salicylic acid (SA) under different irrigation limits (relative water contents of 75%, 60% and 45%, respectively) on the root system growth and leaf antioxidant characteristics. The results showed that with the decrease of lower limit of irrigation, broccoli root length, root fresh and dry weight and catalase (CAT) activity became increased and then went decreased, while shoot ratio, hydrogen peroxide (H2O2) content, activities of super-superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) all gradually became increased. In addition, SA treatment improved root growth characteristics of broccoli, reducing shoot ratio and enhancing the antioxidant enzyme activity of cabbage. It was further discovered that the root growth and antioxidant activity by the 60% limit of irrigation after SA treatment reached similar levels to those by the 75% lower limit of irrigation. It could be concluded that the relative water content of 60% as a lower limit and irrigation approach with 0.15 mmol·L-1 SA treatment could provide theoretical support for the efficient water-saving irrigation on broccoli. |