施硅对水稻铁膜砷固定和体内砷转运的影响

Effects of Silicon Application on Arsenic Sequestration in Iron Plaque and Arsenic Translocation in Rice

水稻铁膜对砷(As)的固定及其体内As的转运深刻影响着糙米中As的累积.施硅(Si)能够抑制水稻对As的累积,然而,施Si如何调控铁膜对As的固定和水稻各部位的As向糙米的转运,相关机制目前尚未十分清楚.以As超标土壤中的水稻铁膜为研究对象,通过开展不同Si处理水平的土壤盆栽试验,研究施Si对水稻根表铁膜固定As和各组织器官中As向糙米转运的影响及作用机制.结果表明,Si_(2)(0.66 g·kg^(-1))处理显著提高了水稻根系CAT(1.81倍)、SOD(7.98倍)和POD(1.25倍)酶活性,增加了铁膜中的DCB-Fe含量(44.35%),提高了铁膜的表面粗糙度(108.91%),导致铁膜的DCB-As含量明显升高(88.32%);而且,Si_(2)处理显著增加了水稻根中As的累积率,降低了根和叶对As的转运能力,最终导致糙米中As含量的显著降低(53.12%).施Si增强水稻根表铁膜对As固定的原因可归结于Si促进铁膜的形成和增大铁膜的表面粗糙度,而施Si抑制根和叶中As向糙米的转运则可能与Si竞争水稻体内As的转运蛋白,促进As-巯基络合物形成以及增强As液泡区隔化等密切相关.研究成果可为稻田As污染阻控技术及产品研发提供科学依据,为华南地区As污染农田的安全利用提供重要参考.

The As sequestration by iron plaque and the As translocation in rice significantly affect the As accumulation in brown rice,and silicon(Si)application inhibits the As accumulation in rice plants.However,little information is available concerning the effect of Si application on As sequestration by iron plaque and translocation in rice.In this study,a pot experiment using As-contaminated paddy soil with different Si supply levels was conducted to investigate the effects of Si application on the As sequestration by iron plaque on the root surface and the As translocation from different tissues to brown rice.The results showed that the Si_(2)(0.66 g·kg^(-1))treatment significantly increased the activities of CAT(1.81 times),SOD(7.98 times),and POD(1.25 times)in the roots,increased the DCB-extractable Fe concentration(44.35%),and promoted the roughness of iron plaque(108.91%),resulting in a significant increase in the DCB-extractable As concentration of iron plaque(88.32%).Moreover,the Si_(2)treatment significantly promoted the As accumulation in the roots and inhibited the As translocation from the roots and leaves to the brown rice,leading to a significant decrease in the brown rice As concentration(53.12%).The increase in As sequestration by iron plaque with Si application was attributed to the enhancement of iron plaque formation and the promotion of surface roughness of iron plaque,whereas the inhibition of As translocation from the roots and leaves to the brown rice in the Si application treatment was closely related to the competition between Si with As for transporters and the promotion of As-thiol complex formation and As compartmentalization in vacuolar.These findings provide more insight into the mechanisms of As translocation in rice and will be helpful for exploring strategies to reduce rice grain As through Si supply in As-contaminated paddy fields in South China.