Influence of Cd2+ on Growth and Chlorophyll Fluorescence in a Hyperaccumulator: Lonicera japonica Thunb.

Chlorophyll fluorescence is an important instrument to study the responses of plants to cadmium (Cd) stress, which in turn can provide a better understanding of Cd tolerance in plants. In the present study, the influence due to cadmium (Cd2+) exposure on growth and chlorophyll fluorescence was investigated in a new hyperaccumulator-Lonicera japonica Thunb. Four levels of Cd2+ (0, 5, 25, and 125 mg kg(-1)) were added to the soil. After 90 days of Cd2+ exposure, maximal photochemical efficiency of photosystem II (F (v)/F (m)) and effective quantum yield of photosystem II (I broken vertical bar PS II) of L. japonica showed an increase under 5 mg kg(-1) Cd2+ exposure, but decreased under higher concentrations of Cd(2+)exposure. However, when Cd concentrations in soil were up to the highest concentrations (125 mg kg(-1)), no significant differences of F (v)/F (m), I broken vertical bar PS II, photochemical quenching, chlorophyll, and carotenoid contents compared with the control were observed. These results indicate that the good tolerance of L. japonica to Cd might result from effective mechanisms including the capacity to maintain good growth, photosynthetic pigment composition, and chlorophyll fluorescence activity, which would be beneficial to enhance the potential for phytoremediation.