Screening Of Low Arsenic Accumulation Rice Materials And Its Arsenic Accumulation Characteristics

As one of the most important food crops in the world,rice has provided food source for more than half of global population.Arsenic pollution is an important factor affecting the safe production of rice,which is characterized by high toxicity,strong mobility and wide pollution area,thereby seriously restricting the safety of rice production.Different genotypes of rice materials are provided with different genetic factors,arsenic tolerance,subcellular distribution and occurrence;moreover,the arsenic absorption and accumulation characteristics and the physiological response characteristics of rice materials of different genotypes are also different,which can provide conditions and basis for the screening of rice materials with low arsenic accumulation.Therefore,the characteristics of arsenic accumulation in rice were explored in this study through the screening of rice materials with low arsenic accumulation in 85 rice materials,with the main research results shown as follows:?1?Compared with the control group(0 mg L^-1),the biomass,total root length and plant height of 85 rice materials were inhibited in varying degrees when exposed to 2 mg L^-1 and 8 mg L^-1 arsenic in the hydroponic experiment.81%of the total samples treated with 2 mg L^-11 arsenic was distributed within 30 mg kg^-1-160 mg kg^-1,78%of the total samples treated with 8 mg L^-1 arsenic was distributed within 45 mg kg^-1-120 mg kg^-1,and the overground arsenic accumulation was mainly distributed in the range of 40?g plant^-1-160?g plant^-1 when exposed to 2 mg L^-11 arsenic,and mainly distributed in the range of 80?g plant^-1-280?g plant^-11 when treated with 8 mg L^-11 arsenic,which indicated the significant difference among different rice materials in the arsenic accumulation capacity,as well as the trend of low accumulation of arsenic,so it was favorable for the screening of rice materials with high arsenic tolerance.After the collection according to the difference in tolerance index,six rice materials with high arsenic tolerance,namely,Huahang No.35,WushanFengzhan,PujiangKangyuan-5-2,CHETUMALA-86,Yakang 2A and Yakang 3A,and five rice materials with low arsenic tolerance,namely,Yahui 2119,Wxj-74,Wxj-380,MR183-2 and IR28153,were obtained.?2?The biomass of rice treated with 30 mg kg^-1 and 90 mg kg^-1 arsenic was inhibited in varying degrees compared with the control group(0 mg L^-1);the arsenic content and accumulation in rice increased with the increase of arsenic concentration,and the difference was significant under the two kinds of arsenic treatment.The arsenic content and accumulation in different organs was also different,namely,root>stem and leaf>grain,under different arsenic concentrations.There was a significant positive correlation between the arsenic treatment concentration and the arsenic accumulation in different organs of the two rice materials with high arsenic tolerance,and all showed root>stem and leaf>grain.The arsenic accumulation in the rice materials with high tolerance was significantly lower than that in the rice materials with low tolerance.The arsenic accumulation in root,stem,leaf and seed of high-tolerance rice variety 2A was 43.07%,57.07%,87.41%and 42.77%respectively of that in low-tolerance rice variety 2119 when treated with 30 mg kg^-1arsenic,and 45.99%,49.58%,53.61%and 27.78%respectively of that in low-tolerance rice variety 2119 when treated with 90 mg kg^-1 arsenic.Two rice materials with low arsenic accumulation,namely,Yakang 2A and Yakang 3A,and one rice variety with high arsenic accumulation,Yaxi 2119 were obtained through cluster screening,which could be used as the parents for breeding the rice materials with low arsenic accumulation.?3?In the two rice materials with low arsenic accumulation,namely,Yakang 2A and Yakang 3A,the content of photosynthetic pigments gradually decreased with the increase in arsenic treatment concentration,but it showed significant increase in the rice materials with high arsenic accumulation when treated with 90 mg kg^-1 arsenic.The chlorophyll fluorescence parameters of rice decreased with the increase of arsenic concentration,and the rice materials with low arsenic accumulation had higher chlorophyll fluorescence parameters.The net photosynthetic rate and stomatal conductance of rice decreased with the increase of arsenic treatment concentration,and the intercellular carbon dioxide concentration of Yakang 2A and Yakang 3A decreased significantly with the increase of arsenic concentration.The ratio of chlorophyll precursor to controlled concentration decreased significantly with the increase of arsenic concentration,and the rice materials with high arsenic accumulation was significantly lower than the low-accumulation materials.The decrease rate of upstream synthesis product of protochlorophyllide was greater than that of the downstream synthesis product when treated with arsenic,which indicated that arsenic could inhibit the synthesis pathway of upstream synthesis product of protochlorophyllide,thus affecting the biosynthesis of chlorophyll.?4?When exposed to high-concentration arsenic,the cell walls of plants would be degraded,some cell chloroplasts would be isolated from the cells,the cell nucleus would enlarge and lose the circular structure,and more metal particles would appear in the cytoplasm,organelles and chloroplasts.Moreover,the chloroplasts would be degraded,resulting in the loss of spindle-shaped structure and many cavities,the grana and inner envelope would be degraded and in loose arrangement,and more metal particles would appear in the chloroplasts.The intercellular metal particles of rice materials with low arsenic accumulation were more abundant than those of rice materials with high arsenic accumulation,indicating that the rice materials with low arsenic accumulation could better adapt to arsenic stress.Through energy spectrum semi-quantitative analysis,it was found that arsenic was mainly concentrated in organelles and cell walls,which first increased and then decreased with the increase of arsenic concentration.The arsenic content in chloroplasts was higher than that in other organelles,so the chloroplasts were analyzed in detail in this study.The arsenic content in chloroplast increased first and then decreased with the increase of arsenic concentration,and the arsenic content in the chloroplast of high-accumulation materials was higher than that in low-accumulation materials.