Abstract: Under enhanced UV-B radiation, 3-year-old seedlings of Larix gmelinii were chose as target to study the impact of exogenous nitric oxide on photosynthetic pigments (Chl a, Chl b and Car) and chlorophyll fluorescence. The results of variance analysis showed 0.5 mmol·L^-1 sodium nitroprusside (SNP), a NO donor, have significant impact on nursery stocks of L.gmelinii under enhanced UV-B radiation stress. 0.5 mmol·L^-1 SNP can significantly inhibited the apparent decline in photosynthetic pigments, F_v/F_m, Φ_PSⅡ,F_v′/F_m′ and qP, and the obvious increase in chl a/chl b, F_o and NPQ after supplement UV-B radiation. All these results indicated that exogenous nitric oxide could reduce the physical damage of photosynthetic reaction centers in seedlings of L.gmelinii under UV-B radiation stress, and enhancement of environmental adaptability of the seedling to supplementary UV-B radiation stress.

Key words: photosynthetic pigments, chlorophyll fluorescence, UV-B radiation, Larix gmelinii