Effects Of Cadmium,Copper And Their Combination Stress On Chlorophyll Fluorescence Parameters Of Spirodela Polyrrhiea (L.) Schleid

Chlorophyll fluorescence technology is based on the photosynthesis theory, which making use of the chlorophyll as the natural indicator to study about the photosynthesis and the influence of kinds of environmental factors on in the plants. It can be used as a effective tool for photosynthesis research as its advantages such as rapidity, sensitivity and non-damage to the cells. It is a useful tool to rapidly reflect the reacts of plants to the pollution.Current international plant chlorophyll fluorescence kinetics in vivo has become a hot spot, but the domestic use of chlorophyll fluorescence of plants under heavy metal stress in the mechanism of photosynthesis, a relatively small change. Therefore, this study was to explore the duckweed in the water culture experiments under heavy metal stress changes in chlorophyll fluorescence parameters and photosynthetic pigment combined with traditional indicators of changes in photosynthesis mechanisms to monitor the water for the use of duckweed quickly provide experimental evidence for heavy metal pollution.The results indicate:1. Cadmium significantly reduced the maximum photochemical quantum yield of duckweed (Fv/Fm), PSII effective quantum yield (ΦPSII), relative electron transport rate (rETR), photochemical quenching (qP) and plastoquinone Library (Fv/2), and increased non-photochemical quenching (qN) and the PSII water splitting level values(Fo/Fv), indicating photosynthetic activity of duckweed in the PSII inhibition by cadmium, you can start the heat dissipation mechanism to prevent the system from further PSII damage. Fo/Fv indicators reflect a sensitive index of photosynthetic damage. Chlorophyll content of duckweed increased as the cadmium concentration decreases. Chlorophyll a and chlorophyll b contents were increased with the concentration of copper increased, the chlorophylla/b ratio increased with increasing copper concentration, indicating more decline in chlorophyll a chlorophyll b.2. Heavy metal copper on the growth of duckweed than on photosynthesis, as demonstrated by indicator of copper stress on the change of quantum yield as sensitive to cadmium stress, but the duckweed non-photochemical quenching parameters increased significantly, indicating that Duckweed may be greatly improved heat dissipation through the protection of PSII systems to reduce the damage of copper on PSII system. Chlorophylla and chlorophyllb contents were increased with the concentration of copper increased, the chlorophylla/b ratio increased with increasing copper concentration, indicating a decline of chlorophyll less than chlorophyll b.3. Heavy metal cadmium, copper and joint stress, significantly reduced the maximum photochemical quantum yield of duckweed (Fv/Fm), PSII effective quantum yield (ΦPSII), relative electron transport rate (rETR), photochemical quenching (qP) and plastoquinone Library (Fv/2), and increased non-photochemical quenching (qN) and the PSII water splitting level (Fo/Fv) values, indicating the PSII photosynthetic activity of duckweed by cadmium, copper and co-suppression, Fo/Fv index is still a reflection of a sensitive index of photosynthetic damage. Chlorophyll a and b increase with the reduction of stress concentration, and chlorophyll a reduction greater than greater than b.4. Whether to join the cadmium or copper to join the combined stress, the quantum yield of duckweed index has dropped, the addition of copper did not reduce the stress of cadmium on the role of duckweed, the addition of cadmium increased the duckweed of stress, the indicators of changes in fluorescence parameters and cadmium, copper and similar common stress. With the increasing concentration of the two composite, the greater the decline in chlorophyll a and b.5. All the stresses are played on Lemna minor growth inhibition, and the higher the concentration, the inhibition became more evident.