不同渗氧能力水稻品种对砷的耐性和积累

Characteristics of arsenic( As) tolerance and accumulation in rice( Oryza sativa L. ) genotypes with different radial oxygen loss

水稻是目前世界上(尤其是东南亚)最主要的粮食作物之一,也是砷(As)通过食物链进入人体的主要途径。日益加剧的土壤砷污染,严重影响了稻米的产量和品质,进而威胁着人体健康。通过温室实验,研究CNT 87059-3、玉香油占和巴西陆稻3种不同渗氧能力的水稻品种在不同砷浓度处理下的生长情况和砷积累特征,结果表明:(1)渗氧能力强的玉香油占砷耐性指数最高,砷处理浓度为2 mg/L时耐性指数高达0.71,而CNT 87059-3的耐性指数为0.55,巴西陆稻仅有0.17;(2)随着砷处理浓度的升高,3种水稻品种的生物量呈现下降趋势,但渗氧能力强的玉香油占较其它两品种生物量的下降幅度小;(3)在不同砷浓度处理下水稻地下部分的砷含量有显著性差异(P<0.001),且同种砷浓度处理下不同水稻品种的地下部分砷含量也存在显著性差异(P<0.01),渗氧能力较强的水稻品种与渗氧能力较弱的品种相比能显著降低砷在根部(地下部分)的积累。水稻渗氧能力与其砷耐性和砷积累有显著相关性,渗氧能力越强,水稻的砷耐性越强,砷的积累量越少。因此,通过筛选渗氧能力强的水稻品种,有望降低污染农田水稻的砷含量和健康风险。

Rice is currently one of the most important foods in the world （especially Southeast Asia）, but arsenic （As） contamination of rice is one of the main pollution pathways into the human food chain. Arsenic contamination of rice not only affects its yield and quality, but also threatens human health. There is an urgent requirement to understand the mechanisms of As tolerance and uptake by rice. In roots, oxygen is required for respiration in order to provide sufficient energy for growth, maintenance and nutrient uptake. However, significant amounts of oxygen loss through the root apex, （with up to 30%-40% of the oxygen being supplied via the root aerenchyma） to the soil is a process termed as radial oxygen loss （ROL）. ROL occurs in the aerated rhizosphere of plant roots growing in waterlogged soil and results in significant changes in soil chemistry within the rhizosphere. Previous studies have shown that ROL was related to As accumulation and speciation, with total ROL from the root system being positively correlated with metal tolerance and negatively correlated with total and inorganic As in rice grains from 20 different genotypes. This paper assesses As tolerance and accumulation in three genotypes namely, CNT 87059-3, IAPAR9 and Yuxiangyouzhan; each possessing different ROL under different As treatments. Experimental results showed that： （1） Root length was significantly different between the three genotypes （〈0.05）, （2） Yuxiangyouzhan had the highest ROL and the greatest tolerance index （0.71） when exposed to 2 mg/L As, （3） the tolerance indices of the three genotypes decreased with increasing As concentration, （4） shoot and root biomass were significantly different between the three genotypes and treatments （P 〈 0.05） and （5） arsenic concentrations in roots were significantly different between the three genotypes （P 〈 0.01） （IAPAR with higher ROL, 336 mg/kg, CNT 87059-3 with lower ROL, 660 mg/kg）, but not significantly different in shoots （P 〉 0.05）. It is concluded that ROL is significantly correlated with As tolerance and accumulation. Rice cultivars with higher ROL have greater As tolerance and lower accumulation. Therefore, ROL can be a potential selection criterion for selecting suitable rice cultivars to grow in areas of high As contamination. This study provides significant findings regarding As tolerance in rice related to ROL and provides potential strategies to mitigate the health risk posed by As contamination. However, the mechanism for As tolerance and accumulation, as well as field application for mitigating As accumulation in rice grains needs further investigation.