Objective   Physiological mechanism and application concentration of foliar quercetin (Q) spray in improving drought resistance of chestnut seedlings were studied.

  Method  In an irrigation-controlled pot experiment, seedlings of Yanbao chestnut (YB) were sprayed Q solutions of concentrations at 600 μmol·L⁻¹ (QD1), 1 200 μmol·L⁻¹ (QD2), 1 800 μmol·L⁻¹ (QD3), 2 000 μmol·L⁻¹ (QD4), and 3 000 μmol·L⁻¹ (QD5), along with one non-spray control under drought (CK1) and another under normal watering condition (CK2). Contents of chlorophyll, malondialdehyde (MDA), and flavonols as well as antioxidant activities of the seedlings were determined.

  Result   The foliar spray of Q significantly elevated the contents of chlorophyll and flavonols as well as the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) and reduced MDA in the seedling leaves over those under CK1, but not to the levels under CK2. The principal component and membership function analyses showed the average drought resistance of QD1, QD2, QD3, QD4, and QD5 to be 0.735, 0.641, 0.738, 1.389, and 0.828, respectively, indicating a superior treatment effect of 2,000μmol Q·L⁻¹.

  Conclusion   Spraying Q solutions on the chestnut seedlings appeared to mitigate cellular damages induced by drought stress. The treatment raised the antioxidant enzyme activities and chlorophyll content while reduced MDA that retarded cell membrane peroxidation on the leaves with the greatest effect displayed by the application of Q at a concentration of 2 000 μmol·L⁻¹.