Abstract: [Objective] In this study, the chlorophyll fluorescence characteristics and growth of Vernicia fordii (tung-oil) seedlings under pesticides stress were analyzed in order to guide tung oil cultivation and provide theoretical references for reducing non-point source pollution in the Three Gorges Reservoir Area.[Method] A pot experiment was conducted to study and compare the chlorophyll contents, chlorophyll fluorescence and growth of tung-oil seedlings under different concentrations of paraquat and fenvalerate-dimerthoate. Levels of paraquat and fenvalerate-dimerthoate were technical/water=1/50, 1/100, 1/200, 1/400 and 1/800 and technical/water=1/125, 1/250, 1/500, 1/1000 and 1/2000, respectively. Water treatment served as control.[Results] Results showed that the chlorophyll content differed under different concentrations of paraquat and fenvalerate-dimerthoate and the chlorophyll content decreased with increasing concentration. These differences were significant in the high concentrations treatment (paraquat ≥1/200 and fenvalerate-dimerthoate ≥1/500). The (F_v/F_m) of PSⅡ, q_P and ETR of tung-oil seedlings under high concentrations of paraquat (≥1/200) and fenvalerate-dimerthoate (≥1/500) were significantly lower than the CK (P<0.05), but the NPQ was obviously higher than the CK (P<0.05). The (F_v/F_m), (q_P), (ETR) and (NPQ) of tung-oil seedlings under the commodity provision concentration of paraquat (1/400) and fenvalerate-dimerthoate (1/1000) were lower than CK with an exception of ETR under the treatment of fenvalerate-dimerthoate, but the differences were not statistically significant. High concentration of paraquat (≥1/200) and fenvalerate-dimerthoate (≥1/500) inhibited the growth of plant height, diameter and biomass per plant of tung-oil seedlings (P<0.05), and the higher the concentration was used the stronger inhibition effect can be detected. Paraquat in the commodity provision concentration (1/400) promoted the growth of plant height, diameter and biomass per plant of tung-oil, while fenvalerate-dimerthoate in the commodity provision concentration (1/1000) inhibited the growth of plant height and biomass per plant of tung-oil, but promoted the growth of diameter. But all the differences in growth were not significant (P>0.05). The root/shoot ratio was inhibited by the high concentrations of paraquat (≥1/200) and fenvalerate-dimerthoate (≥1/500) treatment (P<0.05). Paraquat in the commodity provision concentration (1/400) promoted the root/shoot ratio and fenvalerate-dimerthoate in the commodity provision concentration (1/400) inhibited the root/shoot ratio, but again the differences were not significant (P>0.05).[Conclusion] Our results indicated that high concentrations of paraquat and fenvalerate-dimerthoate obviously decreased the chlorophyll content and photosynthesis of tung-oil seedlings and inhibited the growth of plant height, diameter and biomass per plant, and reduced the root/shoot ratio, which in turn resulted in reduction in root absorption area, and impact on the later growth of tung-oil seedlings. However, paraquat and fenvalerate-dimerthoate with the commodity provision concentrations did not have an obvious effect on photosynthesis and growth of tung-oil seedlings. Therefore, it was safe for spraying pesticide under the commodity provision concentration, which could achieve the good effect of weeding or insecticide and would not harm plants. The results provided guidance for protecting ecological environment and scientific agricultural production in the Three Gorges Reservoir region.

Key words: Vernicia fordii, pesticide stress, chlorophyll fluorescence characteristics, growth