根表铁锰膜对不同生育期水稻吸收和转运As的影响

采用土壤盆栽试验法,研究不同生育期水稻根表铁锰膜形成及其对As吸收和转运的影响。结果表明,两个水稻品种YD6和NK57均在分蘖期形成的铁锰膜量最多,成熟期形成的铁锰膜量最少。水稻根系和茎叶吸收积累As随着水稻不同品种和不同生育期变化较大,As的吸收和积累与铁锰膜形成存在相关性。与分蘖期相比,YD6和NK57成熟期根系As含量分别减少81.6%和62.1%。孕穗期YD6和NK57茎叶As含量分别比分蘖期减少86.4%和65.5%,比成熟期减少87.8%和67.1%。分蘖期水稻根系和茎叶As含量与DCB-Fe或DCB-Mn浓度均呈显著的负相关关系,而孕穗期水稻根系和茎叶As含量与DCB-Fe浓度呈显著的正相关关系,说明不同生育期铁锰膜对水稻植株吸收和转运As的影响不同。两个水稻品种不同生育期,As均主要富集和分配在根表铁锰膜中,铁锰膜中As的分配比率达62.9%～84.9%。NK57从根表铁锰膜、根系和茎叶向籽粒转运As的能力比YD6强,籽粒中As含量是YD6的2.1倍。结果表明可以通过选育As低积累和低转运的水稻品种,来降低污染地区As对人体健康的威胁。

Influence of Iron and Manganese Plaque on Root Surface on Arsenic Uptake and Translocation by Rice (Oryza sativa L.) at Different Growth Stages

The formation of iron and manganese plaque on root surface and the effect of plaque on arsenic uptake and translocation of rice (Oryza sativa L.) at different growth stages were investigated by pot experiments. Results showed that both of cultivar YD6 and NK57 had the highest amounts of iron and manganese plaque at tillering stage, and the lowest one at mature stage. Arsenic uptake and accumulation in roots and shoots varied with different cultivars and growth stages, and there was a correlation between As concentration in roots and shoots and amounts of iron and manganese plaque. Compared with As concentration in roots for YD6 and NK57 at tillering stage, they decreased by 81.6% and 62.1%, respectively at mature stage. As concentration in shoots for YD6 and NK57 at booting stage decreased by 86.4% and 65.5%, compared with tillering stage, and decreased by 87.8% and 67.1%, compared with mature stage. At tillering stage, there was a significant negative correlation between As concentration both in roots and shoots and DCB-Fe (or DCB-Mn), while at booting stage, there was a significant positive correlation between As concentration both in roots and shoots and DCB-Fe. It indicated that the influence of iron and manganese plaque on As uptake and translocation by rice was various at different growth stages. As mainly accumulated and distributed in iron and manganese plaque for these two rice cultivars at different growth stages, which was up to 62.9%-84.9% of total As concentration. The translocation factors of As from iron and manganese plaque, root and shoot to seed for NK57 were greater than that for cultivar YD6. As a result, As concentration in seed for NK57 was 2.1 times of YD6. It suggested that the hazards of As to human health could be avoided by screening rice cultivars with low As accumulation and translocation to cultivate.