Abstract: Taking the test tube ‘Duke’ highbush blueberry (Vaccinium corymbosum) seedlings having been transplanted to the field for 6 months as test materials, this paper studied the effects of exogenous nitric oxide (NO) on their growth, PSⅡ photochemical activity, and antioxidant system under high temperature stress. Applying 0,2, 0,5, and 1,0 mmol·L^-1 of exogenous sodium nitroprusside (SNP) could alleviate the decrease of maximum photochemical efficiency (F_v/F_m), actual photochemical efficiency under light(Φ_PSⅡ), photochemical quench (q_P), and nonphotochemical quench (NPQ) caused by high temperature, and prevented the damage of high temperature on photosynthetic apparatus. Comparing with the control, treatments NO decreased the leaf membrane permeability and MDA content, increased the SOD and CAT activities significantly, and promoted proline accumulation. Appropriate concentration SNP could significantly alleviate the damage of high temperature stress on highbush blueberry seedlings, and 0.5 mmol·L^-1 of SNP had the most satisfactory effect.

Key words: high temperature stress, nitric oxide (NO), highbush blueberry, PSⅡ photochemical activity, antioxidant system, leaf trait, vegetation zone, life strategy, standardized major axis test, strategy displacement.