Wang Xun, Tam Nora Fung-Yee, Fu Shi, Ametkhan Aray, Ouyang Yun, Ye Zhihong
State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, PR China.
Department of Biology and Chemistry, City University of Hong Kong, Hong Kong SAR, PR China State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong SAR, PR China.
Ann Bot. 2014 Aug;114(2):271-8. doi: 10.1093/aob/mcu117. Epub 2014 Jun 19.
Mercury (Hg) is an extremely toxic pollutant, especially in the form of methylmercury (MeHg), whereas selenium (Se) is an essential trace element in the human diet. This study aimed to ascertain whether addition of Se can produce rice with enriched Se and lowered Hg content when growing in Hg-contaminated paddy fields and, if so, to determine the possible mechanisms behind these effects.
Two cultivars of rice (Oryza sativa, japonica and indica) were grown in either hydroponic solutions or soil rhizobags with different Se and Hg treatments. Concentrations of total Hg, MeHg and Se were determined in the roots, shoots and brown rice, together with Hg uptake kinetics and Hg bioavailability in the soil. Root anatonmy was also studied.
The high Se treatment (5 μg g(-1)) significantly increased brown rice yield by 48 % and total Se content by 2·8-fold, and decreased total Hg and MeHg by 47 and 55 %, respectively, compared with the control treatments. The high Se treatment also markedly reduced 'water-soluble' Hg and MeHg concentrations in the rhizosphere soil, decreased the uptake capacity of Hg by roots and enhanced the development of apoplastic barriers in the root endodermis.
Addition of Se to Hg-contaminated soil can help produce brown rice that is simultaneously enriched in Se and contains less total Hg and MeHg. The lowered accumulation of total Hg and MeHg appears to be the result of reduced bioavailability of Hg and production of MeHg in the rhizosphere, suppression of uptake of Hg into the root cells and an enhancement of the development of apoplastic barriers in the endodermis of the roots.
汞（Hg）是一种剧毒污染物，尤其是甲基汞（MeHg）的形式，而硒（Se）是人类饮食中的一种必需微量元素。本研究旨在确定在汞污染的稻田中添加硒是否能产出硒含量增加且汞含量降低的水稻，如果可以，确定这些效应背后的可能机制。
两种水稻品种（粳稻和籼稻）在含有不同硒和汞处理的水培溶液或土壤根袋中种植。测定根、茎和糙米中总汞、甲基汞和硒的浓度，以及土壤中汞的吸收动力学和汞的生物有效性。还研究了根的解剖结构。
与对照处理相比，高硒处理（5μg g⁻¹）使糙米产量显著提高48%，总硒含量提高2.8倍，总汞和甲基汞分别降低47%和55%。高硒处理还显著降低了根际土壤中“水溶性”汞和甲基汞的浓度，降低了根系对汞的吸收能力，并增强了根内皮层质外体屏障的发育。
向汞污染土壤中添加硒有助于产出同时富含硒且总汞和甲基汞含量较低的糙米。总汞和甲基汞积累的降低似乎是由于根际汞的生物有效性降低和甲基汞的产生减少、汞进入根细胞的吸收受到抑制以及根内皮层质外体屏障发育增强的结果。
