| Cadmium is a heavy metal element with high toxicity in the environment.It is highly bio-migratory and can be easily absorbed and accumulated by plants.Cadmium poisoning the plant so that edible part of the cadmium content exceeded,threatening food safety,and harm human health through the food chain.Rice is one of the major food crops of mankind and one of the crops that accumulate cadmium.Therefore,it is very important to take various measures to reduce the cadmium content of rice,especially the edible part,This is very important for the rational use of cadmium pollution in paddy fields,the production of safe rice,the protection of human health.This is also one of the environmental problems to be solved urgently.The results showed that there were significant differences in cadmium content in different parts of rice,especially in grain.The distribution,transport,subcellular distribution and chemical forms of cadmium in different genotypes of rice were different.This is the main reason for the difference of cadmium content.Phosphate can inhibit the absorption of cadmium by plants and alleviate the toxicity of cadmium to plants.However,whether the phosphate has different effects on the cadmium of different genotypes of rice is still to be further studied.The pot experiment was carried out with two genotypes of rice.Shennong 315 is a cadmium-tolerant variety and Huajing 1417 is a cadmium-sensitive variety.This study investigated the effect of phosphorus on cadmium uptake and accumulation in different genotypes of rice.So as to provide the theoretical basis for the selection of low cadmium-accumulating rice varieties in low cadmium-contaminated water fields and the application of appropriate phosphate fertilizer to produce safe rice.The results are as follows:1.Effects of phosphorus on the subcellular distribution of cadmium in different rice varietiesTwo varieties of root and stem of cadmium in the cell wall accounted for the largest,followed by the cell soluble fraction and the cadmium was the smallest in the organelle.The cadmium content of root subcellular subunits was higher than that of stem and leaf.With the increase of phosphorus,the proportion of cadmium in the cell wall of rice root and stem increased significantly,and the most significant effect was when the concentration of phosphorus was 900 mg·kg-1.This indicates that the effect of phosphorus on plant cadmium tolerance is enhanced in its ability to bind cadmium to the cell wall.Shennong 315 is better than Hingjing 1417.2.Effect of phosphorus on chemical forms of cadmium in different rice varietiesIn different phosphorus and cadmium treatment,the chemical form of cadmium showed FNaCl>FHAc>Fw>FE>FHCl as a whole.The root cadmium content is higher than stem and leaf.With the increase of phosphorus,the proportion of extracted acetic acid in cadmium increased significantly,and the proportion of cadmium extracted from cadmium decreased,which may be a detoxification strategy for alleviating cadmium stress.The cadmium content of sodium chloride extracted from Shennong 315 was significantly lower than that of Huajing 1417,and the extracted cadmium content of acetic acid was significantly higher than that of Huajing 1417.3.Effects of phosphorus on cadmium uptake and translocation in different rice varieties at tillering stageThe addition of cadmium at a concentration of 5 mg·kg-1 significantly inhibited the growth of rice at tillering stage and reduced the uptake of phosphorus.The increase of phosphorus promoted the growth of rice,and the content of phosphorus and cadmium in rice was negatively correlated.The effect of applying phosphate fertilizer on the content of cadmium in two cultivars was significantly reduced,and the effect was most significant at 900 mg·kg-1.The cadmium content in root of Shennong 315 was higher than that of Huajing 1417,while the cadmium content in stem and leaf was lower than that in Huajing 1417.This indicated that the enrichment ability of Shennong 315 was strong,and the migration ability of Huajing 1417 was stronger.4.Effects of phosphorus on yield and biomass of different rice varieties at maturity stageThe addition of phosphorus significantly increased the yield and biomass of the two cultivars,and the most significant increase was when the phosphorus concentration was 450 mg·kg-1.However,under the high phosphorus level,the growth of rice was inhibited.In the cadmium control group,the yield and biomass of Huajing 1417 were significantly higher than those of Shennong 315.The addition of cadmium at a concentration of 5 mg·kg-1 significantly inhibited rice yield and biomass,the inhibition of cadmium on Shennong 315 was relatively small,and the yield and biomass of Huajing 1417 were larger.This indicates that the tolerance of cadmium to the two varieties is different.The application of phosphorus could effectively alleviate the stress of cadmium,and it was the best when the concentration of phosphorus was 450 mg ·kg-1.5.Effects of phosphorus on cadmium allocation and grain enrichment coefficient of different rice varieties at maturity stageIn the cadmium control group,the cadmium distribution of roots,stems and leaves of two cultivars was roughly 89:9:2,and the difference was not significant.In the addition of cadmium treatment at a concentration of 5 mg·kg-1,the cadmium distribution of the two cultivars was different,and the enrichment ability of Shennong 315 was significantly higher than that of Huajing 1417.With the increase of phosphorus,the cadmium content of the two cultivars decreased and the enrichment coefficient decreased,and the decrease of Shennong 315 was significant.6.Effects of different phosphorus levels on soil available cadmium contentIncreasing phosphorus can reduce soil available cadmium content,but with the increase in phosphorus to reduce the trend gradually weakened.The available soil cadmium content of the two rice varieties was slightly different but not much difference.This indicated that the difference of phosphorus uptake of different varieties of rice was mainly reflected in the effect of phosphorus on plants. |
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