Abstract: 【Objective】Soil salinity poses a significant challenge to global agriculture. Salt stress inhibits root respiration and disrupts physiological and metabolic activities, impairing essential functions such as absorption and transport. Arbuscular mycorrhizal fungi (AMF), a widespread root symbiotic fungus, enhance plant resistance to salt stress naturally and in an environmentally friendly way. Ultraweak luminescence (UWL) is a natural phenomenon observed in all living organisms, though its mechanisms remain largely unknown. This study focuses on the mitigating effect of AMF inoculation on roots under salt stress by analyzing the relationship between root respiration and UWL. The objectives of this study were to investigate the changes in root respiration, enzyme activities, and UWL intensity after AMF inoculation under salt stress, and to assess the possibility of UWL as a potential indicator of plant physiological status under salt stress. 【Methods】The strawberry cultivar Benihoppe was selected for the experiments. Strawberry seedlings were transplanted into greenhouse pots. The experiment had four treatment groups: AMF inoculation (Glomus mosseae), salt stress, salt stress with AMF inoculation, and a control with sterilized AMF. Seedlings were treated with 90 mmol·L-1 NaCl and Na2SO4 salt solution. Each pot was irrigated with 600 mL of salt solution, while the control group received the same amount of water. Samples were taken after 1, 3, 5, 7, and 9 days of salt stress. The main measurements included root respiration rate, enzyme activities (glucose 6-phosphate dehydrogenase, phosphofructokinase, NAD-malate dehydrogenase), and UWL intensity of roots and leaves. For root respiration rate, enzyme activities, and UWL measurements, samples were taken randomly from roots. For leaves' UWL, three mature leaves of similar length were selected. Each test was repeated three times for accuracy. Statistical analyses were conducted to observe changes in the indicators and assess AMF's effectiveness in mitigating salt stress effects. 【Results】Results showed that salt stress significantly inhibited root respiration and enzyme activities in strawberries. A significant decrease in root respiration and enzyme activities was observed under salt stress. Specifically, glucose-6-phosphate dehydrogenase, phosphofructokinase, and NAD-malate dehydrogenase activities decreased under salt stress, reflecting its negative impact on root respiratory metabolism. Without salt stress, AMF-inoculated plants showed higher and more stable respiration rates, enzyme activities, and UWL intensities compared to controls. This suggests that under normal conditions, AMF inoculation can improve the overall physiological status of the strawberry root system. Under salt stress, AMF inoculation effectively mitigated negative effects, increasing respiration rate, enzyme activities, and UWL intensities compared to non-inoculated controls. These findings suggest that AMF protects root function and metabolic activities under saline conditions. Additionally, there was a positive correlation between UWL intensity, root respiration, and key respiratory enzyme activities in strawberry leaves and roots. 【Conclusion】There is a close relationship between strawberry root respiration intensity, related enzyme activities, and UWL of roots and leaves. Salt stress greatly reduces root respiration rate and respiration-related enzyme activities, associated with oxidative stress processes. Reduced metabolic activities result in lower UWL intensity, reflecting the adverse effects of salinity on the plant's physiological state. AMF inoculation mitigates the inhibitory effects of salt stress on root respiration and enzyme activities, thereby slowing the decrease in UWL intensity. This suggests that under saline conditions, AMF maintains higher metabolic activities and improves the overall physiological status of the root system, enhancing salt tolerance in strawberry plants. These findings highlight the potential of AMF to enhance strawberry salt tolerance by maintaining root respiratory metabolic activity, while the correlation suggests that leaf UWL intensity could serve as a reference for non-invasive indicators of strawberry physiological status under experimental salt stress conditions. This study provides new insights into AMF's protective mechanisms under salt stress and deepens our understanding of plant-stress interactions and AMF's role in enhancing crop stress tolerance.
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