| Sulfonylurea herbicides were extensive used in agricultural field to control broadleaf weeds. Chlorsulfuron is the representative variety of sulfonylurea herbicides. It may persist in soil long enough to damage subsequent crops. Long-term sewage water and industrial wastewater irrigation, mixed dust pollution, and long-term use of pesticides and fertilizers, that will lead to the accumulation of cadmium in soil. Residual chlorsulfuron and Cd co-exist in soil is inevitable, which the effects and mechanism of mixed pollutants on the crop have attracted wide attention. Therefore, the effects of mixed pollutants on the growth, mechanism of antioxidant, photosynthesis, and metabolites and metabolic pathway of maize seedlings and Spinacia oleracea L., were important for food safety evaluation, control of environmental pollution and the relationship between environmental pollution and health.The single and joint effects of chlorsulfuron and Cd applied to soil, on the growth (determined following ISO guidelines) of the maize seedlings and Spinacia oleracea L, were evaluated by compared with the length of shoot and root and the differences of enzyme activities. The effects on the system of photosystem II were evaluated by the change of chlorophyll fluorescence kinetics parameters. The changes of metabolites in two kinds of plants were analysied using 1H-NMR, GC-MS and LC-Q Exactive Orbitrap.Changes of metabolites using a variety of metabonomics technology combined with chlorophyll fluorescence kinetics parameters and the results of physiological and biochemical disclosed that chlorsulfuron, Cd and the mixed affect the multiple metabolic pathways in crops.1. Reactive oxygen species (ROS) were induced by chlorsulfuron, leading to self-protection mechanisms were adopted to counteract oxidative stress, including the activated antioxidant system (the enhanced activity of SOD, CAT and GST, P<0.05), and to repair membrane lipid peroxidation (the increase of MDA in some chlorsulfuron treatment, P<0.05).Chlorsulfuron affect fluorescence yield and electron transport between QA, QB and plastoquinone in Spinacia oleracea L (Fluorescence intensity decreased of OJIP, P<0.05), but no effects on maize seedlings. The photosynthetic reaction center was effected by chlorsulfuron, leading to energy usage and transfer were blocked (the increase of ABS/RC, P<0.05). Self-protection mechanisms were actived to release the excess energy as heat (the increase of DI0/RC, P<0.05). However, there was no effect on reduction of QA and electron transfer (the no changes of TRo/RC and ET0/RC, P>0.05). Moreover, PIABS, a indicator to reponse the state of physiological activity, was increased first then fall. It indicated that low dose of chlorsulfuron induced the plant defense the damage, but high dose of chlorsulfuron caused irreversible damage on crops photosynthetic systems. The changes of physiological and biochemical hampered tricarboxylic cycle (the increase of citric acid and malic acid, P<0.05), resulting in a shift of energy supply from aerobic resiration to anaerobic respiration (the increase of pyruvic acid and lactic acid, P<0.05), and the accumulation of carbohydrate (Sucrose, glucose and fructose, etc) also resposed to the disorder of energy metabolism and cell wall (Galacturonic acid and rhamnose) synthesis. In addition, disordered amino acids metabolism (Branched chain amino acids, aromatic amino acid, serine, glutamic acid, etc) and the increase of the metabolites (glutamine, proline, putrescine, inositol and GAB A) of related to resistance were also observed in chlorsulfuron intoxicated crops.2. Cd did not effect on growth of maize seelings and Spinacia oleracea L and also not induced the accumulation of ROS. So, self-protection mechanisms was not stimulated (the no changes of SOD, POD, CAT and GST, P>0.05) and no accumulation of MDA. There were no changes of related parameters of reaction and dissipation of energy. However, Cd caused the disorder of TCA (the decrease of citric acid and malic acid in maize seedlings, the increase of citric acid and malic acid in Spinacia oleracea L. P<0.05). Cd (5.0mg/kg) induced a shift of energy supply from aerobic respiration to anaerobic respiration in Spinacia oleracea L. (the increase of lactic acid, P<0.05), but there was no effect on maize seedlings (the decrease of lactic acid (P<0.05) and no change of pyruvic acid (P>0.05)). Cd also induced accumulation of putrescine and inositol in maize seelings and induced accumulation of proline and inositol in Spinacia oleracea L. Morover, disordered amino acids metabolism (aspartic acid, glutamic acid, serine, alanine, etc) and accumulation of carbohydrate were obversed in plants under Cd stress.3. Compared with single stress, the content of chlorophyll was increase in maize seedlings and Spinacia oleracea L. under combined polltants stress. It was benefit for the photosynthesis and also stimulated the self-protection mechanism which the activity of antioxidant enzyme (the increase of POD and CAT and the decrease of GST, P<0.05) were higher than single stress to remove ROS. There was no effect on fluorescence yield and the electron transfer between A?QB and plastoquinone in maize seelings (Fluorescence intensity increased of OJIP, P<0.05). Compared with control, there were no change in ABS/RC?DI0/RC and PIABS under 0.001mg/kg chlorsulfuron and Cd stress. There were no changes in ABS/RC?DI0/RC and PIABS under high dose of chlorsulfuron and Cd stress comparing with single stress, it indicated that there was no synergistic effect between chlorsulfuron and Cd. However, the combined pollutants inhibited the fluorescence yield and the electron transfer between QA?QB and plastoquinone in Spinacia oleracea L. The change of ABS/RC, DIo/RC and PIABS under combined stress indicated that Cd aggravated the effects of chlorsulfuron on energy of photosynthetic reaction center. So, there was synergistic effect on photosynthesis in Spinacia oleracea L.The changes of metabolites indicated that there was antagonism effect on isoleucine, valine, serine, lactic acid, etc in maize seedlings, but the rest of the metabolites such as pyruvic acid, malic acid, citric acid and methionine in low concentration composite treatment group were antagonism effect, while high concentration were synergies. Moreover, chlorsulfuron and Cd had a synergies effect on isoleucine, glutamic acid, lactic acid and citric acid, etc in Spinacia oleracea L., the rest of the metabolites such as malic acid, valine gamma-aminobutyric acid in low concentration composite treatment group were synergies effect, while high concentration were antagonism.The results of statistics and quantity showed that reactive oxygen species was induced by chlorsulfuron, leading to self-protection mechanisms were adopted to counteract oxidative stress, including the activated antioxidant system and to repair membrane lipid peroxidation; energy use and transfer in photosynthesis system was liminted by chlorsulfuron; the TCA, part of amino acid metabolism, energy metabolism and cell wall synthesis were limited by chlorsulfuron. Cd (5.0mg/kg) did not significantly affect the growth and photosynthesis of maize seedlings and Spinacia oleracea L., but metabolites and metabolic pathway has been changed in crops. The results also indicated that there was an interaction between chlorsulfuron and Cd. In addition, the biggest difference between mazie seelings and Spinacia oleracea L under stress was the shikimic acid pathway. So, we conclude that some metabolites in this path can be used as a mark for monocotyledon under stress. |
PDF Full Text Request