Abstract:In order to understand the physiological mechanism of UV-B to improve drought resistance of Arabidopsis thaliana, the wild type (Columbia-0, WT) and sto mutant seedlings at 2-week-old were treated with UV-B for one week, and then the seedlings were treated with 30%PEG for 24 hours, the phenotypes of the plants were counted, and the contents of flavonoids, proline and MDA were determined. The results showed that low doses of UV-B pretreatment could enhance drought resistance of A. thaliana, the contents of proline and flavonoids increased for 20%-40% and 50%-65%, respectively, and the cell membrane damage reduced, the water retention was improved. The effect of low dose UV-B in enhancing A. thaliana drought tolerance disappeared in sto mutants, indicating the effect might be related to STO protein in the molecular mechanism.