Effects of Cadmium Stress on Chlorophyll Fluorescence Characteristics of Hedera helix

The Hedera helix cuttings seedlings were used as experimental objects, and hydroponic treatment of different concentrations of CdCl₂ solution was carried out. The effects of cadmium stress on its chlorophyll content and fluorescence parameters were determined and analyzed. Results show that the chlorophyll a, chlorophyll b and total chlorophyll content decrease significantly under cadmium stress, and the chlorophyll a/b ratio increase significantly. Moreover, the chlorophyll a/b ratio increase largely with the increase of the concentration of cadmium stress. Under the cadmium stress of 20 and 80 μmol/L, the maximum optical efficiency, the non-photochemical quenching, the actual photosynthetic efficiency, the photochemical quenching, and the photosynthetic electron transport rate show no significant change, indicating that the chlorophyll fluorescence parameters photosynthetic apparatus of H. helix can keep well stability under the this cadmium concentration. While under the cadmium stress of 200, 400 μmol/L, especially the 400 μmol/L Cd²⁺, can cause damage to its photosynthetic apparatus, manifested by potential maximum photochemical efficiency, actual photochemical efficiency of photosystem Ⅱ, non-photochemical quenching, and significant reduction in electron transport rate. Leaf initial fluorescence is significantly increased. This indicates that cadmium stress at this concentration has an inhibitory effect on the photosynthetic system function of chlorophyll fluorescence parameters of H. helix.