Objective The study aims at exploring the physiological responses of Ormosia henryi seedlings with inoculation of different rhizobium strains under moderate drought stress and screening the excellent strains for drought resistance.

Method  Using O. henryi seedlings inoculated with different rhizobium strains as test material, the continuous drought stress experiment were designed under pot culture. After 23-day's drought stress, the physiological indexes such as relative conductivity, MDA, soluble sugar, free proline content, SOD activity, photosynthetic rate, transpiration rate and chlorophyll fluorescence parameters were determined, and the drought resistance of each treatment seedlings was evaluated by the membership function comprehensive method.

Result  The results showed that the relative membrane of O. henryi seedlings inoculated with rhizobium strains significantly decreased by 29.4%-73.9% under moderate drought stress. Compared with the CK (not inoculated), the average proline content, soluble sugar content and SOD activity increased by 199.8%, 135.3%, and 200.2%, the MDA decreased by 26.2%-78.0%, and the highest photosynthetic rate was 11.6 times higher than that of CK treatment. The light energy conversion efficiency and the potential activity of PS Ⅱ of O. henryi seedlings increased after inoculated with rhizobium strains, the ability of adjusting and adapting to drought stress strengthen.

Conclusion The effect of different strains to drought resistance of O. henryi seedlings shows significant difference (P < 0.05). The comprehensive evaluation results of drought resistance show that the mean value of membership function of O. henryi seedlings inoculated with 6 kind of strains were from 0.62 to 0.81, indicating these seedlings are highly drought resistance treatments, and these strains could be regarded as excellent drought resistant strains.