Influence of Different Artemisinin Concentrations on Physiological Metabolism of Highland Barley Seedlings under Freeze-Thaw Stress

The degradation of ecosystem functions caused by the allelopathic effects of invasive plants is one of the major environmental problems in the world today. In this study, we used highland barley seedlings as experimental materials to explore the physiological effects of freeze-thaw and artemisinin single and multiple stresses, so as to provide a theoretical basis for the scientific planting, management and environmental problems caused by Artemisia annua L. The key results showed that under the same artemisinin concentration stress, compared with the non-freeze-thaw group, the net photosynthetic rate of plateau barley seedlings decreased by 8.35–40.41%, the soluble sugar content decreased by 21.04–29.83%, and the malondialdehyde (MDA) content decreased by 22.57–43.25% (P < 0.05), and the soluble protein content did not change significantly, and the superoxide dismutase (SOD) activity decreased first and then increased, and the SOD activity was the lowest when the artemisinin concentration was 50 mg/L. We hypothesized that SOD activity decreased first and then increased, possibly due to the initial inhibition of enzyme activity by the decrease in temperature, and the accumulation of superoxide in plant cells. Over time, the temperature rises, and the barley seedlings gradually adapt to the environmental changes, while the temperature rises and the SOD enzyme activity increases to break down excess superoxide in the cells. Under the combined stress of freeze-thaw and artemisinin, barley seedlings showed high cold resistance, and artemisinin with a concentration of less than 10 mg/L had a certain effect on the growth of barley seedlings, which could reduce the harm of freeze-thaw to barley seedlings and improve the stress resistance of barley seedlings. Artemisinin at concentrations below 10 mg/L exhibited antagonistic effect when used in combination with freeze-thaw. When the artemisinin concentration was higher than 10mg/L, it would lead to barley seedling cell damage, and high artemisinin concentration showed incomplete synergistic effect with freeze-thawing.