Abstract: In order to measure the effect and action mechanism of cadmium(Cd) on the photosynthetic characteristics in the leaves of flue-cured tobacco,flue-cured tobacco was cultured in a solution containing different concentrations of Cd. The effects of Cd stress on the chlorophyll content,photosynthetic gas exchange and chlorophyll fluorescence parameters in the flue-cured tobacco leaves were investigated. The results showed that the chlorophyll content in the flue-cured tobacco leaves declined as the Cd concentration increased. The chlorophyll a content,in particular,was reduced to a much greater extent than chlorophyll b content. The photosynthetic capacity in the leaves of flue-cured tobacco was reduced mainly associated with the stomatal conductance until the Cd concentration reached 75 μmol/L. But,when Cd concentration reached 100 mol/L,the cause of flue-cured tobacco leaf photosynthetic capacity decreased to were the stomatal and non stomatal factors common restrictions. The non-photochemical queching(NPQ) and the quantum yield of light-dependent and ΔpH-and xanthophyll-mediated regulated thermal dissipation(Y_NPQ) was increased below the 50 μmol/L Cd,that means the flue-cured tobacco leaf was mainly by increasing non-radiative energy dissipation mechanisms by xanthophyll cycle to reduce the flue cured tobacco in excess excitation energy,but with the further increase of Cd concentration,NPQ and Y_NPQ was reduced,which leads to the excess light energy(1-q_P)/NPQ,the quantum yield or flux of thermal dissipation in non-functional PSⅡ and the degree of photoinhibition of PSⅡ reaction center increased dramatically,at this point,the heat dissipation and the reaction center inactivation was the major photoprotective mechanisms in leaves of flue-cured tobacco to defense the Cd poisoning. This study would provide some basic data for seeking Cd-resistant mechanism of tobacco.

Key words: Flue-cured tobacco, Cadmium, Photosynthetic characteristics, Chlorophyll fluorescence

CLC Number: 

• Q945.1

• S572.01