A meta-analysis of elevated O3 effects on the Photosynthesis of Shrubs

In our research, we collected and compiled 100 sets of publicly available O3 fumigation experimental observations from the past 35 years (1990 to 2025), which underwent rigorous quality control and use an integrated meta-analysis, we comprehensively examined the response of shrub photosynthesis to O3, highlighting the effects of O3 concentration, duration of the experiment, and climate type on this response. The results showed that under elevated O3 stress, the chlorophyll content (Chl) and net photosynthetic rate (Pn) of shrubs growing in temperate regions decreased the most, by 24.01% and 48.40%. Different O3 concentrations had significant differences in their impact on the Pn in the shrubs: when the O3concentration was 81–160 nmol/mol, Pn decreased the least, approximately 24.05%. In the same O3 environment, the length of stress time had no significant difference on the Pn of shrubs. However, the length of stress time had a highly significant difference in its impact on the Chl content in the shrubs: when the stress time was 8–15 days, the Chl content decreased the most, approximately 39.87%. Our research demonstrated that under elevated O3 conditions, the duration of stress and the climatic type of the growth region exert a more pronounced influence on chlorophyll (Chl) content, stomatal conductance (Gs), and net photosynthetic rate (Pn) in shrubs. Elevated O3 has the most substantial effect on the photosynthetic parameters of shrubs located in temperate regions. Future research should focus on the stress impacts of elevated O3 on temperate shrubs, and strategies to improve the stress resistance of these shrubs in this region should be investigated.