Solar-induced chlorophyll fluorescence captures the effects of elevated ozone on canopy structure and acceleration of senescence in soybean

Solar-induced chlorophyll fluorescence (SIF) provides an opportunity to rapidly and non-destructively investigate how plants respond to stress. Here, we explored the potential of SIF to detect the effects of elevated O ₃ on soybean in the field where soybean was subjected to ambient and elevated O ₃ throughout the growing season in 2021. Exposure to elevated O ₃ resulted in a significant decrease in canopy SIF at 760 nm (SIF ₇₆₀), with a larger decrease in the late growing season (36%) compared with the middle growing season (13%). Elevated O ₃ significantly decreased the fraction of absorbed photosynthetically active radiation by 8-15% in the middle growing season and by 35% in the late growing stage. SIF ₇₆₀ escape ratio (f _esc) was significantly increased under elevated O ₃ by 5-12% in the late growth stage due to a decrease of leaf chlorophyll content and leaf area index. Fluorescence yield of the canopy was reduced by 5-11% in the late growing season depending on the f _esc estimation method, during which leaf maximum carboxylation rate and maximum electron transport were significantly reduced by 29% and 20% under elevated O ₃. These results demonstrated that SIF could capture the elevated O ₃ effect on canopy structure and acceleration of senescence in soybean and provide empirical support for using SIF for soybean stress detection and phenotyping.