不同渗氧能力水稻品种对砷的耐性和积累

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(P0.001),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(P0.01),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。     

水稻砷污染及其对砷的吸收和代谢机制

水稻是当今世界大部分地区(尤其是东南亚)的主要的粮食作物之一,同时也是砷(As)进入食物链的主要途径之一。日益严重的水稻田As污染,不但影响了稻米的产量和品质,而且通过食物链威胁着人体健康。如何减少水稻地上部(尤其是米粒)As的含量和降低其毒性,及提高水稻As耐性是亟需解决的世界食品安全问题。深入了解水稻对As的吸收、积累和代谢的生理及分子生物学机制是解决水稻As污染的关键途径。综述国内外研究,对今后深入研究提出建议。     

水稻镉积累特性的生理和分子机制研究概述

我国的稻米镉超标对国民身体健康造成严重威胁, 而选育低镉积累的水稻(Oryza sativa)品种是降低稻米镉含量行之有效的策略, 因此有必要了解水稻对镉的积累特性及其生理过程和相关功能基因。该文概述了镉在水稻根部的吸收、木质部中的装载与运输、茎节中的分配、叶片中再分配以及籽粒镉积累等过程的生理和分子机制研究进展, 以期为低镉水稻的选育和安全生产提供理论参考。     

接种AM真菌和施加铁可协同降低水稻砷累积

采用外源添加砷(As)的土培模拟试验探究了接种丛枝菌根真菌(AMF)异形根孢囊霉Rhizophagus irregularis和外源添加铁(Fe)对水稻Oryza sativa根表铁膜形成以及水稻累积砷的影响。结果表明,根表铁膜能够吸附大量的磷和砷。添加砷促进了根表铁膜的形成,而接种AMF后铁膜厚度显著降低。接种AMF改善了植物的磷营养状况,显著提高了水稻根系砷浓度,但降低了地上部砷浓度;砷污染情况下施加铁显著降低了接种处理水稻地上部的砷浓度。接种AMF+施加铁处理降低水稻地上部砷浓度的效果最大。这表明AMF+施加铁可协同抑制水稻地上部砷积累。该研究结果为在高砷背景值土壤中种植粮食作物并保障食品安全提供了一条可供选择的技术途径。     

不同有机肥对土壤镉锌生物有效性的影响

在南方典型稻田设置连续4年施用猪粪、鸡粪、稻草的定位试验,监测施用不同有机肥条件下土壤及水稻植株镉(Cd)、锌(Zn)含量的变化,研究有机肥对土壤Cd、Zn活性及其交互作用的影响.结果表明: 施用有机肥(猪粪、鸡粪、稻草)对土壤全Cd、有效态Cd含量及Cd活性皆无显著影响,但有增加土壤Cd全量的趋势,且显著增加土壤全Zn、有效态Zn含量及Zn活性.施用猪粪、鸡粪、稻草皆可降低稻米Cd含量,降Cd效果为猪粪>鸡粪>稻草,猪粪处理水稻稻米、茎、叶Cd含量分别比对照下降37.5%、44.0%、36.4%;鸡粪处理水稻米、茎、叶Cd含量分别比对照下降22.5%、33.8%、22.7%;而稻草处理水稻米Cd含量比对照下降7.5%,但茎、叶Cd含量比对照分别增加8.2%、22.7%;施用猪粪、鸡粪降低稻米Cd含量主要是降低了水稻植株对土壤Cd的富集,而施用稻草则主要是降低了水稻茎Cd向稻米的转运.施用有机肥还增加了水稻茎Zn含量,施用猪粪、鸡粪、稻草的水稻茎Zn含量比单施化肥分别增加53.4%、41.2%、13.9%,但对水稻稻米、叶Zn含量无显著影响.Zn、Cd在土壤、植株茎中皆表现出显著的拮抗作用,土壤及水稻茎Zn含量的增加显著抑制了水稻米、茎、叶对Cd的吸收积累,且随土壤有效态Zn/Cd含量比值的增加,Zn、Cd竞争土壤吸附不是抑制水稻吸收积累Cd的主控因子,而Zn、Cd竞争吸收才是影响水稻吸收积累Cd的主控因子.     

不同有机肥对土壤镉锌生物有效性的影响

在南方典型稻田设置连续4年施用猪粪、鸡粪、稻草的定位试验,监测施用不同有机肥条件下土壤及水稻植株镉(Cd)、锌(Zn)含量的变化,研究有机肥对土壤Cd、Zn活性及其交互作用的影响.结果表明:施用有机肥(猪粪、鸡粪、稻草)对土壤全Cd、有效态Cd含量及Cd活性皆无显著影响,但有增加土壤Cd全量的趋势,且显著增加土壤全Zn、有效态Zn含量及Zn活性.施用猪粪、鸡粪、稻草皆可降低稻米Cd含量,降Cd效果为猪粪>鸡粪>稻草,猪粪处理水稻稻米、茎、叶Cd含量分别比对照下降37.5%、44.0%、36.4%;鸡粪处理水稻米、茎、叶Cd含量分别比对照下降22.5%、33.8%、22.7%;而稻草处理水稻米Cd含量比对照下降7.5%,但茎、叶Cd含量比对照分别增加8.2%、22.7%;施用猪粪、鸡粪降低稻米Cd含量主要是降低了水稻植株对土壤Cd的富集,而施用稻草则主要是降低了水稻茎Cd向稻米的转运.施用有机肥还增加了水稻茎Zn含量,施用猪粪、鸡粪、稻草的水稻茎Zn含量比单施化肥分别增加53.4%、41.2%、13.9%,但对水稻稻米、叶Zn含量无显著影响.Zn、Cd在土壤、植株茎中皆表现出显著的拮抗作用,土壤及水稻茎Zn含量的增加显著抑制了水稻米、茎、叶对Cd的吸收积累,且随土壤有效态Zn/Cd含量比值的增加,Zn、Cd竞争土壤吸附不是抑制水稻吸收积累Cd的主控因子,而Zn、Cd竞争吸收才是影响水稻吸收积累Cd的主控因子.     

基于定量评价方法研究不同水稻品种的镉积累差异

为筛选出高产且适用于粮食安全生产的镉低积累水稻品种，本研究以18个早、中、晚熟稻品种为供试材料，比较了不同品种水稻在中轻度镉污染农田的生长情况以及对镉吸收、积累差异，并通过综合定量评价方法进行评估。结果表明：根据综合定量筛选评价方法将糙米镉浓度、稻谷产量、转运系数和秸秆积累量作为评价指标并赋予不同权重，通过计算综合得分筛选出的高产且镉低积累水稻品种有JR-9(沪香粳106)、JR-2(沪早香软1号)、JR-7(8333)、JR-15(宝农34)和JR-8(南梗9108);品种JR-8水稻产量最高，品种JR-9、JR-7和JR-15水稻产量均显著高于其他品种；不同水稻品种的稻米镉含量差异较大，JR-9、JR-15、JR-7稻米镉含量显著低于其他水稻品种；品种JR-2转运系数最低，更多的镉保留在秸秆中，表现出最高的秸秆积累量，最终成为候选品种。本研究采用的综合定量评价方法可对高产、低Cd的水稻品种进行科学评价，并初步筛选了5个适用于中轻度Cd污染农田推广的Cd低积累水稻品种，其稻米Cd含量达到国家粮食安全限量标准。     

水稻锌铁转运蛋白ZIP基因家族研究进展

锌(zinc, Zn)和铁(iron, Fe)是水稻(Oryza sativa L.)生长必需的矿质元素,也是人体必需的微量元素。水稻体内Zn、Fe含量维持在适宜水平有利于提高其产量和品质,提高稻米中Zn、Fe含量能够在一定程度上解决人体Zn、Fe营养缺乏的问题。因此,研究水稻中Zn和Fe等微量元素转运蛋白的具体功能对于提高水稻产量和稻米品质具有重要意义。锌铁转运蛋白(zinc-regulated transporters and iron-regulated transporter-like protein, ZIP)负责Zn和Fe等离子的吸收、转运和分配,是维持水稻中Zn和Fe平衡的重要转运蛋白,其表达水平受Zn和Fe水平影响。ZIP基因家族在自然群体中具有丰富的等位变异,而且某些单倍型存在明显的籼粳分化,这可能造成了不同品种间籼、粳稻中Zn和Fe积累的差异。目前,已有大量关于ZIP基因家族的研究,但只有OsZIP3的作用机制研究的较为清楚。另外,对Zn、Fe在籽粒中的积累机制研究和自然群体中ZIP基因的等位变异研究还不够深入。因此,ZIP转运蛋白家族仍存在较大的研究空间。本文详细介绍了ZIP转运蛋白在水稻体内的亚细胞定位、表达模式、转运机制以及在自然群体中的等位变异等,以期为研究水稻稻米微量元素的积累提供理论基础,为提高稻米品质提供借鉴。     

稻米镉积累的铁肥调控

以FeSO4和EDTA二钠亚铁（EDTA·Na2Fe,也称EDTA二钠铁）为铁肥,通过土施和叶片喷施研究不同形态铁肥及施肥方式对水稻（Oryza Sativa L．）镉积累的影响．结果显示不论施用何种形态铁肥或何种施用方式对水稻生长和产量性状均没有不利影响．土施EDTA·Na2Fe显著降低了水稻根系、地上部以及稻米（糙米和精米）中的镉含量,并且两基因型水稻精米中的镉含量远低于0．2mg／kg,达到国家限制标准．但土施FeSO4、叶面喷施FeSO4及叶面喷施EDTA·Na2Fe处理均显著增加了根系、地上部及稻米（糙米和精米）中的镉含量．结果还显示施用铁肥可显著提高稻米的铁、铜、锰含量,同时对锌含量也有影响．研究结果认为土施EDTA·Na2Fe等络合态亚铁肥,维持土壤中较高的有效态铁含量以及亚铁含量是控制稻米镉积累的一条新型可行途径．     

稻田硒循环转化与水稻硒营养研究进展

稻田土壤氧化还原电位的交替变化和土壤组分的特殊性决定了硒在稻田环境中的循环转化机制明显有别于旱地土壤,并且影响到土壤硒的有效性及水稻对硒的吸收与积累.深入研究稻田土壤硒的循环转化及水稻硒营养吸收对实现土壤无机硒向有机硒的转化具有重要意义.本文对稻田土壤硒的循环机制及形态转化、水稻体内硒的代谢机制及吸收积累特性进行综述,分析硒在土壤 水稻系统中转化及向水稻体内迁移的研究现状与发展趋势,为土壤硒有效性研究及培育富硒营养稻米提供参考.     

Phytoremediation of arsenic contaminated soil by Pteris vittata L. II. Effect on arsenic uptake and rice yield

A greenhouse experiment evaluated the effect of phytoextraction of arsenic from a contaminated soil by Chinese Brake Fern (Pteris vittata L.) and its subsequent effects on growth and uptake of arsenic by rice (Oryza sativa L.) crop. Pteris vittata was grown for one or two growing cycles of four months each with two phosphate sources, using single super phosphate (SSP) and di-ammonium phosphate (DAP). Rice was grown on phytoextracted soils followed by measurements of biomass yield (grain, straw, and root), arsenic concentration and, uptake by individual plant parts. The biomass yield (grain, straw and rice) of rice was highest in soil phytoextracted with Pteris vittata grown for two cycles and fertilized with diammonium phosphate (DAP). Total arsenic uptake in contaminated soil ranged from 8.2 to 16.9 mg pot(-1) in first growing cycle and 5.5 to 12.0 mg pot(-1) in second growing cycle of Pteris vittata. There was thus a mean reduction of 52% in arsenic content of rice grain after two growing cycle of Pteris vittata and 29% after the one growing cycle. The phytoextraction of arsenic contaminated soil by Pteris vittata was beneficial for growing rice resulted in decreased arsenic content in rice grain of <1 ppm. There was a mean improvement in rice grain yield 14% after two growing cycle and 8% after the one growing cycle of brake fern.     

碳酸钙对水稻吸收重金属(Pb、Cd、Zn)和As的影响

选用重金属(Pb、Cd、Zn)和As复合污染土壤进行水稻盆栽试验,结果表明,碳酸钙的添加显著提高了土壤pH值,显著降低了土壤中交换态Pb、Cd、Zn和As的含量,与对照相比,交换态Pb、Cd、Zn和As含量分别最多降低了98.35%,93.72%,98.52%和69.48%。碳酸钙对水稻根、稻谷干重和总生物量没有显著影响,添加量过高时显著降低了水稻分蘖数和茎叶干重,说明过量施用碳酸钙对水稻生长会产生负面作用。因为碳酸钙的添加,水稻植株各部位重金属Zn含量显著降低,糙米中Zn含量最多减少了34.95%;根、谷壳中Pb、Cd含量显著降低,但糙米中含量却未显著降低;水稻各部位As含量均没有显著降低。参照《食品中污染物限量》(GB2762—2012),试验糙米中Pb、Cd、无机As含量均未达到限量标准。显然,碳酸钙的添加降低了Pb、Cd、Zn的生物有效性(水稻根系对Pb、Cd、Zn的吸收累积减少),但并未有效地抑制Pb、Cd向糙米转运;碳酸钙显著降低了土壤的交换态As含量,但并未使土壤中As的生物有效性明显降低(水稻植株各部位的As含量并未显著减少)。     

Urinary and Dietary Analysis of 18,470 Bangladeshis Reveal a Correlation of Rice Consumption with Arsenic Exposure and Toxicity

Background

We utilized data from the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh, to evaluate the association of steamed rice consumption with urinary total arsenic concentration and arsenical skin lesions in the overall study cohort (N=18,470) and in a subset with available urinary arsenic metabolite data (N=4,517).

Methods

General linear models with standardized beta coefficients were used to estimate associations between steamed rice consumption and urinary total arsenic concentration and urinary arsenic metabolites. Logistic regression models were used to estimate prevalence odds ratios (ORs) and their 95% confidence intervals (CIs) for the associations between rice intake and prevalent skin lesions at baseline. Discrete time hazard models were used to estimate discrete time (HRs) ratios and their 95% CIs for the associations between rice intake and incident skin lesions.

Results

Steamed rice consumption was positively associated with creatinine-adjusted urinary total arsenic (β=0.041, 95% CI: 0.032-0.051) and urinary total arsenic with statistical adjustment for creatinine in the model (β=0.043, 95% CI: 0.032-0.053). Additionally, we observed a significant trend in skin lesion prevalence (P-trend=0.007) and a moderate trend in skin lesion incidence (P-trend=0.07) associated with increased intake of steamed rice.

Conclusions

This study suggests that rice intake may be a source of arsenic exposure beyond drinking water.     

The influence of chemical form and concentration of arsenic on rice growth and tissue arsenic concentration

Arsenic absorption by rice (Oryza sativa, L.) in relation to the chemical form and concentration of arsenic added in nutrient solution was examined. A 4 × 3 × 2 factorial experiment was conducted with treatments consisting of four arsenic chemical forms [arsenite, As(III); arsenate, As(V); monomethyl arsenic acid, MMAA; and dimethyl arsenic acid, DMAA], three arsenic concentrations [0.05, 0.2, and 0.8 mg As L^-1], and two cultivars [Lemont and Mercury] with a different degree of susceptibility to straighthead, a physiological disease attributed to arsenic toxicity. Two controls, one for each cultivar, were also included. Arsenic phytoavailability and phytotoxicity are determined primarily by the arsenic chemical form present. Application of DMAA increased total dry matter production. While application of As(V) did not affect plant growth, both As(III) and MMAA were phytotoxic to rice. Availability of arsenic to rice followed the trend: DMAA<As(V)<MMAA<As(III). Upon absorption, DMAA was readily translocated to the shoot. Arsenic(III), As(V), and MMAA accumulated in the roots. With increased arsenic application rates the arsenic shoot/root concentration decreased for the As(III) and As(V) treatments. Monomethyl arsenic acid (MMAA), however, was translocated to the shoot upon increased application. The observed differential absorption and translocation of arsenic chemical forms by rice is possibly responsible for the straighthead disorder attributed to arsenic.     

Comparative Proteomic Analysis of Rice Shoots Exposed to High Arsenate

Consumption of arsenic contaminated water and cereals is a serious threat to humans all over the world. Rice (Oryza sativa“Nipponbare”), as a main cereal crop, can accumulate arsenic more than 10-fold ...     

砷对农田生态系统污染效应的试验研究

本文通过盆栽及模拟试验,研究了砷对农田生态系统中农作物、土壤微生物、土壤动物的污染效应。结果表明,砷对农作物生长发育有明显不良影响,浓度过高,产量下降并造成农作物体内砷的残留累积;不同种类农作物对砷的敏感程度不同,以对水稻的危害最严重,其次为春小麦、玉米;不同形态砷化物的污染效应有显著差别,亚砷酸盐的毒性最强,砷酸盐次之,硫化砷的影响最小。 砷对土壤微生物具有明显抑制作用,使土壤细菌总数降低,投加亚砷酸钠5ppm,砷酸氢二钠10ppm时,细菌总数开始减少。对土壤固氮菌、解磷细菌、纤维分解细菌等土壤有益微生物有明显抑制作用,使存活率下降。砷污染土壤活性降低,土壤呼吸强度下降。 砷污染影响土壤中蚯蚓的数量与分布,当砷在100—300ppm时,可使蚯蚓致死,死亡率达50—80％。砷在蚯蚓体内明显富集,富集系数为1.32—7.44。     

Arsenic uptake and accumulation in rice (Oryza sativa L.) irrigated with contaminated water

Long-term use of arsenic contaminated groundwater to irrigate crops, especially paddy rice (Oryza sativaL.) has resulted in elevated soil arsenic levels in Bangladesh. There is, therefore, concern regarding accumulation of arsenic in rice grown on these soils. A greenhouse pot experiment was conducted to evaluate the impact of arsenic-contaminated irrigation water on the growth and uptake of arsenic into rice grain, husk, straw and root. There were altogether 10 treatments which were a combination of five arsenate irrigation water concentrations (0–8 mg As l^–1) and two soil phosphate amendments. Use of arsenate containing irrigation water reduced plant height, decreased rice yield and affected development of root growth. Arsenic concentrations in all plant parts increased with increasing arsenate concentration in irrigation water. However, arsenic concentration in rice grain did not exceed the maximum permissible limit of 1.0 mg As kg^–1. Arsenic accumulation in rice straw at very high levels indicates that feeding cattle with such contaminated straw could be a direct threat for their health and also, indirectly, to human health via presumably contaminated bovine meat and milk. Phosphate application neither showed any significant difference in plant growth and development, nor in As concentrations in plant parts.     

Arsenic biotransformation and volatilization in transgenic rice

? Biotransformation of arsenic includes oxidation, reduction, methylation, and conversion to more complex organic arsenicals. Members of the class of arsenite (As(III)) S-adenosylmethyltransferase enzymes catalyze As(III) methylation to a variety of mono-, di-, and trimethylated species, some of which are less toxic than As(III) itself. However, no methyltransferase gene has been identified in plants. ? Here, an arsM gene from the soil bacterium Rhodopseudomonas palustris was expressed in Japonica rice (Oryza sativa) cv Nipponbare, and the transgenic rice produced methylated arsenic species, which were measured by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). ? Both monomethylarsenate (MAs(V)) and dimethylarsenate (DMAs(V)) were detected in the roots and shoots of transgenic rice. After 12 d exposure to As(III), the transgenic rice gave off 10-fold greater volatile arsenicals. ? The present study demonstrates that expression of an arsM gene in rice induces arsenic methylation and volatilization, theoretically providing a potential stratagem for phytoremediation.     

Dietary Arsenic Intake in Taiwanese Districts with Elevated Arsenic in Drinking Water

Inorganic arsenic in dietary staples (i.e., yams and rice) may have substantially contributed to exposure and adverse health effects observed in an endemic Taiwanese population historically exposed to arsenic in drinking water. Observations of this population were used by the U.S. Environmental Protection Agency to derive toxicity values that form the basis for arsenic risk assessment and various regulations in the United States. However, data were previously insufficient to accurately estimate dietary intake. Rice and yam samples collected in 1993 and 1995 from Taiwanese districts with endemic arsenic were analyzed for total arsenic and for inorganic and organic mono and dimethylarsenic. The acid digestion techniques used in the analyses are among the best to preserve organic arsenic in the test sample. Furthermore, concurrent analyses of the proportion of inorganic arsenic in split samples of rice and yams collected in the 1995 investigation were in good agreement, despite using a different digestion method. These data support a likely mean dietary intake of 50?µg/day with a range of 15 to 211?µg/day. Consideration of dietary intake may result in a downward revision of the assumed potency of ingested arsenic as reflected in EPA's toxicity values.