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。     

砧用南瓜幼苗对镉的耐性和积累能力研究

采用营养液栽培的方法,研究了不同浓度（0、5和10 mg·L^-1）镉（Cd）对10种砧用南瓜幼苗生长状况、丙二醛（MDA）、地上部Cd含量及转移系数（TF）的影响,利用隶属函数法综合评价其耐Cd能力与Cd吸收积累能力,以期筛选到优良的砧用南瓜。结果表明：（1）‘多美109’、‘鑫力3号’、‘强力1号’、‘黑籽南瓜’和‘云南黑籽南瓜’在2种浓度Cd处理下全株生物量均显著低于对照,并以‘黑籽南瓜’和‘云南黑籽南瓜’下降幅度最大、耐性最差,而‘野木一雄’、‘青佳砧甲’、‘津油108’和‘抗线1号’在 Cd处理下均与对照差异不显著,生长势良好,耐性强。（2）在2种浓度Cd处理下,‘津油108’幼苗体内各抗氧化酶活性较高,根系和叶片的 MDA含量与对照无显著差异,未受到膜脂过氧化伤害;‘野木一雄’ 幼苗各抗氧化酶活性较高,MDA含量升高幅度较小,为对照的1.01~1.56倍,受到膜脂过氧化伤害相对较小;而‘多美109’、‘强力1号’和‘云南黑籽南瓜’ 幼苗在2种浓度Cd处理下,各抗氧化酶活性显著下降,体内MDA含量升高幅度大,分别为对照的1.30~2.46、1.33~3.11、1.45~3.24倍,受伤害程度最大。（3）‘津油108’与‘青佳砧甲’在2种浓度Cd处理下地上部Cd含量和TF均较小,Cd吸收能力最弱,其次是‘野木一雄’,而‘亮丽佳’、‘黑籽南瓜’和‘云南黑籽南瓜’地上部Cd含量和TF最大,Cd吸收能力最强。（4）隶属函数值综合评价结果显示,10种砧用南瓜幼苗对Cd的耐性大小依次为：‘津油108’＞‘野木一雄’＞‘鑫力3号’＞‘青佳砧甲’＞‘抗线1号’＞‘多美109’＞‘黑籽南瓜’＞‘亮丽佳’＞‘强力1号’＞‘云南黑籽南瓜’。研究认为,砧用南瓜品种对镉胁迫的耐受性存在明显差异,并以‘津油108’最佳,其在镉胁迫下生长势良好,耐性强,且镉吸收和转运能力最弱。     

海马齿对无机汞的耐性和吸附积累

报道了海马齿(Sesuvium portulacastrum)对重金属汞的耐性和吸附特性。 在10 μmol·L^-1汞胁迫时, 海马齿中脯氨酸含量明显低于对照; 丙二醛(MDA)含量、根的电解质外渗率(Electrolyte leakage rate, ELR)无明显变化; 叶绿素含量增加; 植物生长良好, 形态、生长速率、鲜重和根的长度与对照无区别, 且有新的须根形成。结果表明: 低浓度汞对海马齿的生长发育起着促进作用。海马齿能大量吸附积累汞离子, 主要积累在根组织中。当培养液中汞浓度为50 μmol·L^-1时, 海马齿根中汞含量最高可达到33.9 μg·g^-1DW, 是相同处理下地上部分的70倍。培养液中汞浓度为10 μmol·L^-1时, 植物并未受到伤害, 且能快速生长, 此时根部的汞含量可达到12.02 μg·g^-1 DW。由此可见, 海马齿植物表现为很强的耐汞和吸收汞特性。     

柠檬香蜂草对铜的耐性及其积累特征研究

以柠檬香蜂草(Melissa officinalis)幼苗为材料,设置不同浓度Cu~(2+)胁迫(CK、200、400、800和1 000mg·kg~(-1))盆栽实验,测定胁迫0、7、14、21、28d后植物生物量、叶绿素含量、抗氧化酶活性、可溶性蛋白含量、丙二醛(MDA)含量以及植物体内Cu含量等指标,探讨柠檬香蜂草对Cu~(2+)的耐受性及其积累特征。结果表明:(1)相同处理时间下,柠檬香蜂草除MDA含量外其他所有指标均随着Cu~(2+)胁迫处理浓度的增加呈低浓度促进、高浓度抑制的变化趋势,且高浓度组(800和1 000mg·kg~(-1))与低浓度组(200和400mg·kg~(-1))之间差异显著(P0.05);MDA含量在1 000mg·kg~(-1)浓度下持续增长至第14天后开始下降。(2)柠檬香蜂草体内Cu的积累量随Cu胁迫浓度的升高呈先增加后减少的趋势,并在浓度为400mg·kg~(-1)时达到最高值(0.71mg/盆)。(3)在整个胁迫过程中,柠檬香蜂草植株的铜富集系数及其耐性系数均随Cu浓度的增加而减小,各处理浓度对Cu的耐性系数均大于0.5,富集系数均大于1。研究发现,柠檬香蜂草对Cu胁迫具有一定耐受性和富集能力,具有成为铜污染土壤修复植物的潜力。     

水稻对缺氧胁迫的响应及耐性鉴定

水稻对缺氧胁迫的响应及耐性鉴定吴九根（广州市农业科学研究所,５１０３１５）唐建军,宋松泉（中山大学生命科学学院,广州５１０２７５）１．稻田土壤的氧气供给氧气是绿色高等植物行使高效代谢和完成正常生长发育过程的必要条件之一。即使是起源于湿热沼泽生境的水稻...     

三种观赏植物对重金属镉的耐性与积累特性

通过盆栽实验,对镉(Cd)胁迫下3种观赏植物含羞草、白雪姬和树马齿苋的生长、生理和重金属累积与分布情况进行了研究。结果表明:含羞草、白雪姬和树马齿苋的平均耐性指数分别为105.57、81.35和79.88;在100mg.kg-1Cd浓度下三者叶绿素a、b的含量分别为对照的83.74%、69.83%;60.64%、51.26%和60.64%、51.26%;类胡萝卜素的含量和叶绿素a/b值无明显变化;三者在Cd胁迫下均表现出O2.-离子生成速度上升,MDA含量增加,电导率升高的趋势,其中含羞草的变化幅度最低,白雪姬次之,树马齿苋最高。三者对Cd的耐性表现为含羞草白雪姬树马齿苋。3种观赏植物对Cd均具有较强累积能力,在土壤Cd含量为100mg.kg-1时,三者根和地上部分的Cd累积浓度均高于100mg.kg-1。且对Cd积累能力为树马齿苋含羞草白雪姬。含羞草、白雪姬和树马齿苋在土壤Cd污染的治理中有一定的应用价值。     

不同荞麦品种对铅胁迫的耐性差异

用不同浓度的铅处理荞麦7 d后,研究了植株对铅胁迫的耐性差异。结果表明,低浓度铅胁迫对荞麦根的生长表现出一定的促进作用;随着铅浓度的升高,根系生长受到抑制程度加重,但不同品种之间有差异,其中以西荞1号抑制最为严重,九江苦荞比较轻微,晋荞1号处于二者之间。在高浓度铅处理下(1 500μmol.L-1),不同荞麦品种的质膜相对透性均比对照有不同程度上升,以西荞1号升高幅度最大,九江苦荞变化相对较小;而叶绿素a、叶绿素b以及总叶绿素含量均有不同程度下降,其中西荞1号下降幅度最大,九江苦荞变化较小;植株可溶性蛋白质含量均低于对照,其中西荞1号下降幅度最大,而九江苦荞几乎没有变化。所测试的3个荞麦品种对耐铅性存在明显差异,其中以九江苦荞耐铅能力最强,西荞1号最差。     

水稻对重金属镉的吸收及耐性机理研究进展

Cd是一种不能降解、广泛存在于环境中的金属污染物,是植物体非必需元素、环境中生物毒性最强的重金属元素之一,主要来源于矿山开采、火力发电、机械加工,汽车尾气排放以及磷肥生产等。Cd可通过水稻根部进入机体,向地上部分迁移并蓄积,严重影响水稻正常生长, 并引起稻米Cd污染,通过食物链危害人类健康。从水稻Cd吸收影响因素及Cd在水稻中的吸收、运输和积累机理理等方面对水稻Cd污染研究现状进行综述,系统阐述了土壤pH、Eh、离子浓度等条件对水稻Cd吸收的影响,同时讨论了水稻对Cd胁迫的耐性机理及其分子机制。并指出存在的问题和研究方向。     

古老铅锌矿区生态型东南景天对锌耐性及超积累特性的研究

 植物长期生长在重金属污染的生境中,逐渐进化成不同的生态型。通过调查中国东南部古老Pb/zn矿和非矿山生境中的植物种群,发现生长在古老Pb／Zn矿的东南景天(Sedum alfredii Hance)是一种新的Zn超积累植物。在自然和控制条件下,古老Pb／Zn矿生态型比非矿山生态型植株的茎粗、叶片大、植株高。在矿山土壤Zn有效含量为105.5～325.4mg·kg-1时,矿山生态型东南景天植株地上部Zn含量为4134～5000mg·kg-1;当营养液中Zn浓度为1223.6μmol时,其Zn含量高达2％。在相同Zn浓度下,矿山生态型地上部Zn含量比非矿山生态型高30倍左右。两种生态型体内Zn分布也不同,古老铅锌矿山生态型的不同器官中Zn含量以茎>叶片>根系,而非矿山生态型则以根系>茎>叶片。古老铅锌矿山生态型地上部积累的Zn占植株总积累量的90％以上,其中叶片和茎分别占41.66％±5.46％和54.75％±5.87％;非矿山生态型各器官中积累的Zn远远低于古老铅锌矿山生态型,各器官中积累的Zn以茎>根系>叶片。本研究表明,这两种生态型东南景天的发现,为今后探讨植物耐高Zn胁迫和超积累Zn的微进化过程提供了非常有价值的材料,也为Zn污染土壤的植物修复提供了一种很有潜力的候选材料。     

不同水稻品种在不同光照条件下的光合特性及干物质积累

对12个杂交水稻品种在两类生态条件下的光合特性及干物质积累进行了研究.结果表明：水稻适应环境的能力主要由其自身因素决定,品种之间存在较大差异.品种间的净光合速率和叶绿素含量差异均比生态区域间的差异更显著.产量与总干物质量和净光合速率呈显著正相关,决定系数R2分别为0.584和0.590,与茎鞘物质输出率和茎鞘物质转换率相关不显著.与低光强地区相比,高光强地区叶片厚度和干物质积累量增加,茎鞘物质输出率和茎鞘物质转换率降低.在光照充足的条件下,产量中来自于后期光合积累物质的比例较大;在光照不足的条件下,产量中来自于前期干物质积累及其转运的比例较大.     

Effect of polyamines on ribonuclease activity of rice (Oryza sativa L.)

The RNA content and RNase activity were determined during maturation and germination of rice seeds. The RNA content reached a maximum after the 16th day from anthesis but RNase activity steadily increased up to the last stage of maturation. During germination RNA content was greatest after 24 hr and associated with a very low level of RNase activity. Maximum RNase activity was observed at 72 hr from germination and it afterwards gradually declined. During germination, exogenous application of polyamines decreased the level of RNase activity. RNase was partially purified (448-fold) from 72 hr germinated embryonic axis. Effects of polyamines and other divalent cations were observed on the purified enzyme.     

水稻根系通气组织与根系泌氧及根际硝化作用的关系

通过根箱土培试验研究了不同产量籼稻品种中旱22(ZH,高产品种)及禾盛10号(HS,低产品种)苗期根系生长、通气组织发育、根系径向泌氧量(radial oxygen loss,ROL)以及根表和根际土壤硝化强度差异。结果表明,除水稻播种40 d时二者根数量和根干重无显著差异外,ZH根直径、根数量和根干重均显著高于HS,二者差异尤其表现在根系生物量差异。两个水稻品种在距根尖20 mm处均可见辐射状通气组织,ZH皮层薄壁细胞已经完全崩溃形成连接中柱和外皮层的纵向气腔,而HS皮层薄壁细胞未发生完全离解,但仍能观察到明显的连接中柱和外皮层的纵向气腔的形成。同时ZH外皮层厚壁细胞体积较小,排列紧密,细胞壁增厚程度大;而HS外皮层厚壁细胞体积相对较大,排列疏松,细胞壁增厚程度相对较小。表明高产品种通气组织发育比低产品种更加完善,表现为ZH根孔隙度(porosity of root,POR)显著高于HS,且高产品种对水稻根系ROL的屏蔽作用较低产品种更强,为根系提供更充足的氧气供应,促进根系生长。除了水稻播种后40 d时ZH和HS单根ROL无显著差异外(P<0.05),ZH单株、单位重量以及单根ROL均显著高于HS(P<0.01)。两个水稻品种硝化强度均表现为根际土壤显著高于根表土壤 (P<0.01),前者大约是后者的3-6倍。两个品种根表土壤硝化强度无显著差异,而ZH根际土壤硝化强度均显著高于HS。相关性分析结果表明水稻根际土壤硝化强度和整株水稻ROL呈极显著正相关关系(r=0.803,P<0.01),和水稻POR也呈现极显著正相关关系(r=0.808,P<0.01),同时和根系直径、数量和干重均呈极显著正相关关系(P<0.01)。而根表土壤硝化强度和以上指标均无相关关系。由于硝化作用是好氧过程,因此高产品种由于根系发达,通气组织发育好,相应ROL也较大,造成根际土壤氧气含量高,从而可能导致根际土壤硝化强度显著高于低产品种。     

Silicon decreases chloride transport in rice (Oryza sativa L.) in saline conditions

Silicon can alleviate salt damage to plants, although the mechanism(s) still remains to be elucidated. In this paper, we report the effect of silicon on chloride transport in rice (Oryza sativa L.) seedlings in saline conditions. In the absence of salinity, silicon enhanced the growth of shoots, but not roots in three cultivars (cv. GR4, IR36, and CSR10). Salinity reduced the growth of both shoots and roots in all three genotypes. In saline conditions, addition of silicon to the culture solution again improved the growth of shoots, but not of roots. Under these saline conditions, the concentrations of chloride in the shoot were markedly decreased by adding silicon and the ratio of K⁺/Cl⁻ was significantly increased, while the concentration of chloride in the roots was unchanged. The decrease in chloride concentration in the shoot was correlated with the decrease in transpirational bypass flow in rice, as shown by the transport of the apoplastic tracer trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS). Addition of silicon increased the net photosynthetic rate, stomata conductance, and transpiration of salt-stressed plants in cv. IR36, indicating that the reduction of chloride (and sodium) uptake by silicon was not through a reduction in transpiration rate. Silicon addition also increased the instantaneous water use efficiency of salt-stressed plants, while it did not change the relative growth rate of shoots. The results suggest that silicon addition decreased transpirational bypass flow in the roots, and therefore decreased the transport of chloride to the shoot.     

三种不同泌氧能力的红树植物对铅、锌、铜的耐性研究

红树林是分布于热带、亚热带潮间带的典型滨海生态系统。近年来,随着城市化和工业化的发展,滨海生态系统受重金属(例如铅、锌、铜等)的污染越来越严重,我国南方一些红树林底泥中的重金属浓度已达到甚或超过重度污染标准。由于沉积作用,红树林底泥被认为是一个能积累由潮水和河流淡水携带来的重金属的"库"。然而,红树植物具有很强的耐性生长于重度污染的底泥, 但其中的机理目前尚不清楚。由于长期被水淹没,红树林底泥是一个具氧化还原势低,还原性毒性物质(如Fe²⁺、Mn²⁺、H₂S、CH₄等)积累多,营养物质缺乏等特征的厌氧环境。为了适应这种生境,红树植物也进化出了一套与其他湿地植物类似的适应机制,植物能通过通气组织将地上部分的氧气输送到地下,一部分满足根的呼吸作用需要,一部分则通过根释放到根际,这被称为根的泌氧。根的泌氧可以氧化根际环境并且氧化还原性的毒性物质,以保证红树植物根免受毒害而延长生长。因此,根际泌氧是红树植物能适应生境的一个重要机理。本研究试图揭示红树植物在长期适应生境的过程中已经进化和发展出一系列形态解剖和生理生化特征是否在耐浸水的土壤条件,解除Fe²⁺、Mn²⁺等元素的毒性同时,是否也能解除其他重金属(铅、锌、铜)的毒性。通过对木榄、桐花和白骨壤三种不同泌氧能力的植物进行8周室内砂培试验发现:(1)三种植物的生长都被铅、锌、铜所抑制;(2)三种植物对铅、锌、铜都具有一定的耐性,然而,泌氧能力较弱的木榄比泌氧能力较强的桐花和白骨壤对铅、锌、铜的耐性高。     

Transport of DMAA and MMAA into rice (Oryza sativa L.) roots

Arsenate (As(V)) transport into plant cells has been well studied. A study on rice (Oryza sativa L.) showed that arsenite is transported across the plasma membrane via glycerol transporting channels. Previous studies reported that the dimethylarsinic acid (DMAA) and monomethylarsonic acid (MMAA) uptake in duckweed (Spirodela polyrhiza L.) differed from that of As(V), and was unaffected by phosphate (H₂PO₄). This article reports the transport mechanisms of DMAA and MMAA in rice roots. Linear regression analysis showed that the DMAA and MMAA uptake in rice roots increased significantly (p ≤ 0.0002 and ≤0.0001 for DMAA and MMAA, respectively) with the increase of exposure time. Concentration-dependent influx of DMAA and MMAA showed that the uptake data were well described by Michaelis-Menten kinetics. The MMAA influx was higher than that of DMAA. The DMAA and MMAA uptake in rice roots were decreased significantly (p ≤ 0.0001 and ≤0.0077 for DMAA and MMAA, respectively) with the increase of glycerol concentration indicating that DMAA and MMAA were transported into rice roots using the same mechanisms of glycerol. Glycerol is transported into plant cells by aquaporins, and DMAA and MMAA are transported in a dose-dependent manner of glycerol which reveals that DMAA and MMAA are transported into rice roots through glycerol transporting channels. The DMAA and MMAA concentration in the solution did not affect the inhibition of their uptake rate by glycerol.     

根区通氧状况对水稻幼苗生长及吸收镉的影响

采用水培的方法研究了根区通氧状况对水稻根系结构、根系泌氧、根表铁膜生成以及水稻耐受、吸收Cd的影响.水培条件下,根区氧处理对水稻幼苗的生长产生了一定的影响,缺氧条件下的水稻根的伸长量降低,生物量增加,直径增粗,根系泌氧量增加,并降低幼苗对Cd的吸收.当培养溶液Cd2+浓度为1.0 mg/L时,缺氧处理相对于通氧处理,根表吸附的Cd降低了85 5%,地下部分吸收的Cd降低了35%,转运到地上部分的Cd降低了58%.根表铁膜对Cd的吸收和转运也有一定的抑制作用,但其作用因环境中Cd2+浓度和根区通氧状况而异.在根区通氧充分的培养条件下,水稻幼苗铁膜对较高浓度Cd2+(1.0 mg/L)的吸收和转运起着重要的作用,DCB-Cd占根系吸收Cd的50%,茎叶对Cd的吸收显著降低(p<0.05).研究表明在缺氧胁迫下,根系结构本身(如根表通透性降低)是影响水稻吸收Cd的重要因素.     

Effects of phosphate on arsenate and arsenite sensitivity in two rice (Oryza sativa L.) cultivars of different sensitivity

Arsenate and arsenite sensitivity and arsenate influx tests were conducted for two rice cultivars of different arsenic sensitivity, Azucena and Bala. These were to establish if the mechanism of reduced arsenic sensitivity is achieved through an altered phosphate uptake system, as shown for Holcus lanatus. High phosphate treatments (≥50 μM) provided protection against both arsenate and arsenite. Unlike the H. lanatus tolerance mechanism, in the less sensitive cultivar Bala, arsenate influx did not decrease with phosphate treatment and phosphate transporters appeared to be constitutively upregulated; V_max for arsenate influx remain similar when Bala was grown in the presence or absence of phosphate (V_max - 0.90 and 0.63 nmol g⁻¹ f.wt min⁻¹ respectively). Although mean K_m appear different, Bala did not show lower affinity to arsenate than Azucena in the absence of phosphate (K_m - Azucena, 0.30 mM and Bala, 0.18), while in phosphate treatment, Bala arsenate affinity was half that observed for Azucena (K_m - Azucena, 0.14 and Bala, 0.36 mM). These were low compared to a 4 and 6 fold decrease seen for similar studies on H. lanatus in the absence and presence of phosphate. Phosphate-induced arsenic protection was observed but the mechanism does not resemble that of H. lanatus. Alternative mechanisms were discussed.     

Mapping QTL for Biomass Yield and Its Components in Rice (Oryza sativa L.)

Addicive effects, additive by additive epistatic effects, and their environmental interactions of QTLs are important genetic components of quantitative traits. Genetic architecture underlying rice biomass yield and its two component traits (straw yield and grain yield) were analyzed for a population of 125 DH lines from an inter-subspecific cross of IR64/Azucena. The mixed-model based composite interval mapping approach (MCIM) was used to detect QTLs, There were 12 QTLs detected with additive main effects, 27 QTLs involved in digenic interaction with aa and/or aae effects, and 18 QTLs affected by environments with ae and/or aae effects. It was revealed that epistatic effects and QE interaction effects existed on biomass yield and its component traits in rice. In addition, the genetic basis of relationships among these traits were investigated. Four QTLs and one pair of epistatic QTLs were detected to be responsible for the positive correlation between biomass yield and straw yield. Three QTLs might be responsible for the negative correlation between straw yield and grain yield. This result could partially explain the genetic basis of correlation among the three traits, and provide useful information for genetic improvement of these traits by marker-assisted selection.     

Grain dormancy,peroxidase activity and oxygen uptake in Oryza sativa

In developing grains of rice (Oryza sativa L.) of the dormant variety H4, peroxidase activity decreased sharply about a week before grain maturity without any change in grain dormancy and oxygen uptake of intact grain. During storage or after-ripening of mature dormant intact grains of four varieties (H4, H6, Mayang Ebos and Seraup 27) at 25–30°, the critical range in peroxidase activity was 1·0–1·4 μmol purpurogallin/hr/grain above which rice grains were almost completely dormant and below which the grains were almost completely nondormant. The oxygen uptake of intact H4 grain tended to decrease during the loss of dormancy. The decrease in both the peroxidase activity and oxygen uptake could be attributed mainly to the lower activities of the hull. Dehulling of developing and mature H4 grains reduced dormancy and increased the oxygen uptake of the grain. Thus, reduction by the hull of the level of oxygen available to the dehulled grain (embryo) was mainly responsible for grain dormancy in rice.     

Different isoforms of starch-synthesizing enzymes controlling amylose and amylopectin content in rice (Oryza sativa L.)

Starch, composed of amylose and amylopectin, greatly influences rice cooking and textural quality, which in turn is controlled by various isoforms of several enzymes. Activity of one or more isoforms of starch‐synthesizing enzymes results in various forms of starch structure based on the amylopectin chain length and average external, internal and core chain length distribution and hence results in varying physicochemical and cooking quality. Since the synthesis of starch is highly complex, it is crucial but essential to understand its biosynthetic pathway, starch structure and effects on the physicochemical properties that control eating and cooking quality, and alongside conduct research on gene/QTL mapping for use in marker-assisted selection (MAS) with a view to improve and select cultivars with most desirable range and class of rice starch properties. This article presents the updates on current understanding of the coordination among various enzymes/isoforms towards rice starch synthesis in endosperm and their effect on rice grain physicochemical, cooking and eating qualities. The efforts in identifying regions responsible for these enzymes by mapping the gene/QTLs have provided a glimpse on their association with physicochemical and cooking properties of rice and, hence, improvement is possible by modifying the allelic pattern, resulting in down or nil regulation of a particular enzyme. The clear understanding of the tissue specific coordination between enzyme isoforms and their subsequent effect in controlling eating and cooking properties will enhance the chances to manipulate them for getting desired range of amylose content (AC) and gelatinization temperature (GT) in improved cultivars through combining desired alleles through MAS.