叶面喷施纳米MnO_(2)对水稻富集镉的影响机制

Effect and Mechanism of Foliar Application Nano-MnO on Cadmium Enrichment of Rice

镉(Cd)容易被水稻富集,从而造成稻米中Cd含量超标,严重威胁人类健康.锰(Mn)是植物必需元素,为了探究叶面喷施纳米MnO_(2)对水稻富集Cd的影响机制,本研究在酸性Cd污染土壤上进行田间小区试验,在水稻抽穗早期叶面喷施0.1%、0.3%和0.5%的纳米MnO_(2)溶液.结果表明与对照组相比,叶面喷施不同浓度的纳米MnO_(2)可以有效降低水稻叶、壳和糙米中的Cd含量,增加所有部位的Mn含量,但对水稻的产量影响不大.叶面喷施纳米MnO_(2)后,提高了叶片光合作用效果,抑制了叶片脂质过氧化,增加了氧化应激酶的含量,从而缓解Cd对水稻的胁迫.此外,叶面喷施纳米MnO_(2)增加了水稻根表铁锰胶膜的含量,强化了铁锰胶膜对Cd的吸附/共沉淀作用,从而限制水稻根系吸收Cd.因此,在水稻抽穗早期叶面喷施纳米MnO_(2)是一种增加糙米中Mn含量和减少Cd含量的有效措施.

Cadmium(Cd)is easily enriched in rice,resulting in an excessive Cd content in the grain,which seriously threatens human health.Manganese(Mn)is an essential element of plants.In a field experiment on Cd-contaminated acid soils,we investigated the effectiveness and mechanism of Mn in minimizing Cd accumulation in rice via foliar spraying using 0.1%,0.3%,and 0.5%nanoMnO_(2)solutions at an early stage of heading.Compared with a control treatment,foliar spraying effectively reduced the Cd content of rice leaves,husks,and brown rice;increased the Mn content of all rice organs;but had no effect on rice yield.Foliar application of nano-MnO_(2)alleviated the plant stress induced by Cd by improving leaf photosynthesis,inhibiting lipid peroxidation,and increasing the content of the oxidative stress protein kinase.In addition,foliar application of nano-MnO_(2)limited the absorption of Cd by roots by increasing the content of iron-manganese plaque on the surfaces of rice roots and strengthening its adsorption/co-precipitation of Cd.Therefore,foliar application of nano-MnO_(2)during the early stages of rice heading is an effective measure to increase the Mn content and reduce the Cd content of brown rice.