Effects Of Silicon And Phosphorus On Cadmium Uptake And Accumulation In Rice

Cadmium is one of the main pollutants in the soil and a heavy metal with high toxicity.Rice is the main staple food of human beings.Heavy metals in the soil can be assimilated by rice and enter the human body through the food chain,posing a threat to human health.At home and abroad,there have been a lot of reports on the application of different amendments to alleviate the toxicity of heavy metals to rice.Among them,the alleviation of silicon and phosphorus on cadmium toxicity in rice has been recognized by scholars at home and abroad.However,most of these studies have focused on single modifiers,or the improvement of heavy metal contaminated soil by silicon and phosphorus application,or the mitigation of rice growth under heavy metal stress.The studies on the mechanism that two elements are co-administered to alleviate cadmium stress in rice are still very few.Therefore,this study investigated the growth of rice,and absorption,metastasis,subcellular distribution,chemical morphology of cadmium in two different genotypes of rice?Shendao 529 and Shendao 47?by pot experiment.Combined with hydroponic experiments,take sensitive rice varieties?Shendao 529?as experimental metarial,use real-time quantitative PCR technology,the regulation of cadmium-related genes in rice by silicon and phosphorus was explored.The main findings are as follows:1.Effect of combined application of silicon and phosphorus on rice growth statusWhen the application of silicon and phosphorus is more than the single element of silicon or phosphorus,the increase of rice SPAD value,yield and biomass is more significant.When the concentration of 1.2 g·kg^-1 silicon and 0.45 g·kg^-1 phosphorus were applied,the yield and biomass of the two rice varieties reached the highest,and the yield increase effect of Shendao 529 was better than that of Shendao 47.2.Effects of Combined Application of Silicon and Phosphorus on Cadmium Uptake and Metastasis in RiceUnder cadmium pollution stress,the cadmium content of Shendao 529 was lower than that of Shendao 47.The combined application of silicon and phosphorus effectively reduced the cadmium content in all parts of rice.When the concentration of 1.2 g·kg^-1 of silicon and 0.45 g·kg^-1 of phosphorus were applied,the cadmium content in roots and stems and leaves of rice reached the lowest,and the reduction of each part is higher than the reduction of single element application.Compared with the two varieties of rice,the transfer coefficient of stems of Shendao 47 was more significant.3.Effects of combined application of silicon and phosphorus on the distribution of cadmium subcellular cells in various parts of riceUnder the combined application of silicon and phosphorus,the decrease of cell wall percentage in rice roots was greater than that in stems and leaves.The combined application increased the ratio of cadmium in cell wall to the total cadmium content of subcellular cells,and reduced the cadmium content in organelles.The ratio of cadmium content,and the magnitude of change is greater than the single element application.Silicon and phosphorus effectively increased the cadmium fixation of rice cell wall under cadmium stress and alleviated the toxicity of rice to organelles.However,there were some differences in the regulation of cadmium subcellular distribution in different genotypes of rice.The change of cell wall ratio of Shendao 47 was higher than that of Shendao 529 after silicon and phosphorus application.4.Effects of combined application of silicon and phosphorus on cadmium chemical forms in different parts of riceThe effect of combined application of silicon and phosphorus on the change of cadmium content in stems and leaves of rice was greater than that in roots.Silicon and phosphorus effectively reduced the ratio of sodium chloride binding state and ethanol binding state of cadmium in different parts of rice in two varieties,and increased the distribution ratio of water soluble state and acetic acid combined state of cadmium.Silicon and phosphorus effectively reduced the cadmium content of rice with higher activity and toxicity,and alleviated the toxicity of cadmium to rice.However,the effects of the application on the morphological distribution of cadmium in two different genotypes were slightly different.The overall variation trend of the morphological proportion of Shendao 47 was slightly higher than that of Shendao 5295.Effects of combined application of silicon and phosphorus on the expression of cadmium-associated transporter genes in riceWith the application of silicon and phosphorus,the cadmium content in all parts of rice decreased.When the concentration of 284 mg·kg^-1 silicon and 180 mg·kg^-1 phosphorus were combined applied,the content of cadmium in the roots and stems of rice reach the lowest.After application of silicon and phosphorus,the expression of Os LCT1 and LCD gene was down-regulated,and the expression of Os Nramp5 gene was up-regulated.The effect of the combination of the two genes on the relative expression of the three genes was better than that of the single element.Under cadmium stress,silicon and phosphorus were effectively involved in the regulation of rice cadmium-related transport genes and inhibited the transport of cadmium by rice.