Keywords: 
• mercury /
• tobacco /
• chlorophyll /
• photosynthetic effect

Abstract: In order to study the influence of different concentrations of mercury (Hg) on the photosynthesis of tobacco, seedlings of three tobacco cultivars (Cuibi 1, K326 and Yunyan 87) from Fujian Province were pot-planted, and treated with Hg under six varied concentrations (0, 1, 2, 4, 8, 16 mg·kg^-1). The results showed that: (1) No significant difference is observed in the chlorophyll content in the leaves of three tobacco cultivars (P > 0.05) when compared with control group, but F_v/F_m, F_v/F_o, PIABS show decreasing trend with the increase of Hg concentration. There is no correlation between chlorophyll content and photosynthesis intensity of tobacco under Hg stress. (2) OJIP curve shape changes under the stress of higher concentration of Hg (4 mg·kg^-1). Hg affects the photosynthetic apparatus of tobacco leave, which is mainly related to the mechanisms that the PSII and photosystem reaction center are damaged and photosynthetic electron transport process is inhibited. This may explain the significant decrease of tobacco photosynthesis effect. (3) The specific activity parameters ABS/RC, TR_o/RC, DI_o/RC are positively correlated with Hg concentration, and ET_o/RC and RC/CS_o are negatively correlated with Hg concentration in PSII unit reaction center of tobacco leaves. Tobacco leaves dissipate excessive light energy and improve the consumption of excessive energy to protect the photosynthetic apparatus from greater harm under the stress of higher concentration of Hg, which shows strong self-adjustment ability.