根表铁膜对水稻吸收转运稀土元素Ce的影响

采用溶液培养的方法探讨根表铁膜形成对水稻吸收积累和转运稀土元素Ce的影响。结果表明,Ce污染胁迫可抑制水稻根表铁膜的形成,根表铁膜吸附的Ce量随着溶液中Ce浓度的提高而增加。根表铁膜形成可降低水稻根系但提高水稻茎叶对Ce的吸收积累。当溶液中Ce浓度为0.1、0.5和1.0 mmol·L~(-1)时,铁膜诱导组水稻根系Ce含量分别比非诱导组水稻根系Ce含量降低38.60%、45.94%和32.75%,诱导组水稻茎叶Ce含量分别比非诱导组水稻茎叶Ce含量提高42.37%、28.87%和22.62%。根表铁膜形成可影响Ce在水稻植株中的富集和转运能力。非诱导组水稻根系富集Ce的能力远大于茎叶。诱导组水稻根系对Ce的富集能力最强,其次是根表铁膜,最后是水稻茎叶。诱导组水稻根系Ce转运系数显著大于非诱导组的根系,说明根表铁膜形成可促进水稻根部Ce向茎叶中转运。可见,根表铁膜对水稻吸收转运稀土元素的影响机理比较复杂。     

根表铁膜对水稻铅吸收转运的影响

通过温室土壤盆栽试验研究不同生育期水稻根表铁膜形成对水稻吸收和转运Pb的影响。结果表明,两种水稻根表铁膜形成量(以DCB-Fe含量计)及铁膜中吸附的Pb量均随着生育期的延长而减少。水稻根表铁膜Fe含量与铁膜吸附的Pb量呈显著的正相关关系(r=0.798,p0.01)。水稻根系和茎叶吸收积累Pb随着不同品种和不同生育期而变化。品种NK57籽粒Pb含量显著高于品种YD6,前者为后者的1.9倍。从富集系数和分配比率来看,Pb主要富集在水稻的铁膜和根系中,而积累在茎叶和籽粒中的比率较少。Pb从水稻根表铁膜、根系和茎叶向籽粒中的转运系数在两个水稻品种间差异均不显著。水稻分蘖期和孕穗期根表铁膜量与根系Pb含量均呈显著的正相关关系(p0.05),但是成熟期水稻根表铁膜量与根系、茎叶和籽粒中Pb含量相关性均不显著,说明根表铁膜形成对水稻分蘖期和孕穗期吸收积累Pb有一定影响,但对水稻成熟期根系、茎叶和籽粒吸收积累Pb影响不大。     

砷-硒交互作用对水稻吸收转运砷和硒的影响

采用溶液培养法,研究了两种形态无机As与四价Se交互作用对水稻吸收转运As和Se的影响.结果表明,不同形态As与Se交互作用对水稻吸收转运As和Se影响较大,Se(Ⅳ)显著地提高水稻根系而降低水稻茎叶对As的吸收积累.与对照处理相比,在1.0μmol·L-1As(Ⅲ)和As(Ⅴ)处理下添加1.0μmol·L-1Se(Ⅳ)分别导致水稻根系As含量提高59.5%和21.3%,而水稻茎叶As浓度减少10.4%和21.9%.As(Ⅲ)或As(Ⅴ)处理显著降低水稻茎叶对Se的吸收积累,但As(Ⅴ)处理对水稻根系积累Se没有影响.在1.0μmol·L-1Se(Ⅳ)处理下,添加1.0μmol·L-1As(Ⅲ)和1.0μmol·L-1As(Ⅴ)导致水稻茎叶Se浓度分别比对照处理降低41.9%和30.3%.Se(Ⅳ)与As(Ⅲ)或As(Ⅴ)对水稻转运As、Se的能力具有交互拮抗作用.研究结果表明,在As污染农田中,可通过施用Se肥来提高植物的Se营养,降低植物对As的吸收积累,从而降低As对人体健康的危害.     

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。     

水稻根表铁膜对水稻根吸收铅的影响

采用土-砂联合培养方法诱导水稻根表形成不同数量的铁膜:高铁膜(HP)和低铁膜(LP),探讨铁膜形成的多少对水稻离体根系吸收铅的影响.结果表明,在水稻生长期间,水分显著影响根表形成铁膜的数量.水稻吸收的铅大部分结合在根组织中(平均75%),少部分富集在根表铁膜中(平均25%).与低铁膜相比,高铁膜可以增强铅在水稻根表铁膜和根中的积累,由此可见,铁膜可能在一定程度上促进铅向水稻根内的转运.     

砷污染土壤中不同基因型水稻根表铁膜的形成及其对砷吸收和转运影响

采用土壤盆栽试验法,研究6个不同基因型水稻品种根表铁膜形成及其对As吸收、转运的影响。结果表明,水稻形成根表铁膜在不同基因型品种之间差异显著（p<0.001）,其中品种94D-22形成铁膜量（以Fe含量计）是品种圭630的1.5~1.8倍,添加As处理对水稻根表铁膜形成影响不显著。低As含量的对照土壤中,水稻根表铁膜量与根系As含量存在着显著的正相关关系（r=0.657,n=24,p<0.01）,与As转移系数呈显著的负相关关系(r=-0.612,n=24,p<0.01）。土壤添加As后,水稻根表铁膜量与茎叶As含量存在显著的正相关关系（r=0.653-0.673,n=24,p<0.01）,与As转运之间无显著相关性。比较生长于As污染土壤的不同水稻品种,科优1360茎叶积累As较少,且其根系转运As能力也较差,而品种94D-22正好相反。研究结果表明,在As含量较低的土壤中,水稻根表铁膜的存在可成为根系As的障碍层,阻止As向地上部转运;但在As含量较高的土壤,根表铁膜的存在却促进了水稻茎叶对As的积累,其对As的转运没有显著影响。人们可通过作物品种筛选来防治土壤As污染危害、降低As对人体健康的威胁。     

盆栽水稻对土壤汞富集特征及其影响因素

通过室内水稻盆栽实验,研究了苏南水稻土在外源无机汞及秸秆还田条件下,成熟期水稻不同器官对汞(Hg)的富集行为,并对稻米Hg积累的影响进行分析。结果表明,土壤外源Hg明显抑制水稻生长,表现为根部、秸秆生物量及产量均显著下降,平均分别下降35%、24%和35%。相同土壤条件下,盆栽稻米Hg含量基本上低于野外调查结果,表明野外稻米中Hg的来源具有多元性特点,也存在其他室内外差异因素的影响。土壤中添加外源Hg,可明显增加成熟期水稻各器官对Hg的富集,稻米、稻壳和秸秆Hg含量平均分别提高220.9、39.5和97.8μg·kg~(-1)。在不同盆栽土壤中,秸秆还田对外源Hg向水稻各器官迁移的影响存在异同。土壤pH、CEC、有机质和碳酸钙均可影响稻米对土壤中外源Hg的吸收。稻米富集Hg的能力强于稻壳,土壤中添加外源Hg条件下,稻米对Hg的富集能力提升速率明显高于秸秆。     

砷-铅交互作用对水稻根表铁膜富集及根系吸收砷铅的影响

采用土-砂联合培养方法诱导水稻根表自然形成铁氧化物膜,研究了As-Pb交互作用对水稻根表铁膜吸附砷铅及根系吸收As和Pb的影响.结果表明,As和Pb的添加显著地影响水稻根表铁膜对As和Pb的吸附,并且As-Pb交互作用显著地影响水稻根系对两元素的吸收及根表铁膜对As的吸附.添加Pb可促进水稻根系对As的吸收.当As浓度为25μmol.L-1时,浓度为25μmol.L-1Pb处理与对照相比导致水稻根系吸收As提高了53.3%.同样,施用As也可以促进水稻根系对Pb的吸收,当Pb的浓度为25μmol.L-1和50μmol.L-1时,50μmol.L-1As处理与对照相比,水稻根系吸收Pb分别提高20.2%和28.6%.添加As显著地促进Pb由铁膜向根系中转运,而添加Pb对As由铁膜向根系中的转运影响不大.因此,在重金属复合污染情况下,水稻根表铁膜对重金属的吸附及根系对重金属的吸收均存在着复杂的交互作用.     

微藻对无机汞和甲基汞的吸附和吸收特性

本文选取蛋白核小球藻和斜生栅藻两种微藻作为研究对象,将其接种于含有低浓度无机汞(0.1—2.0μg·L~(-1))和甲基汞(5.0—100 ng·L~(-1))的培养基中,考察两种藻的耐受性及微藻对无机汞及甲基汞的吸附和吸收特性.结果表明,在实验浓度范围内,0.1μg·L~(-1)的无机汞和5.0 ng·L~(-1)的甲基汞即可抑制蛋白核小球藻和斜生栅藻的生长,抑制作用随汞浓度的升高而增强.超过60%的无机汞和70%的甲基汞在24 h内通过吸附和吸收快速转移到了微藻,只有少量汞化合物残留于培养基中,168 h后,两种藻对无机汞和甲基汞的最高去除率分别为99.75%和99.82%.单个微藻细胞对于无机汞和甲基汞的吸附和吸收均在24 h达到最大值,随培养时间的延长,细胞增殖产生的稀释效应导致单细胞吸附量和吸收量逐渐降低.实验中观察到了无机汞和甲基汞在微藻细胞表面吸附及内部吸收的转换.     

两种通气组织不同的水稻品种根表铁膜的形成及砷吸收积累的差异（Differences of Iron Plaque Formation and As Accumulation between Two Rice Cultivars with Different Aerenchyma Tissue）

采用土壤盆栽试验方法,比较了两种通气组织结构不同的水稻品种(扬稻6号和农垦57)根表铁膜的形成及其吸收积累As的差异.结果表明,通气组织结构不同对水稻根表铁膜的形成及其对As的吸收积累有显著影响.通气组织结构发达的扬稻6号根表铁膜数量和铁膜中As含量均显著高于农垦57,扬稻6号根表铁膜量为431.53g·kg-1,铁膜中As含量达到220.2mg·kg-1,分别是农垦57的1.3和1.7倍.发达的通气组织结构显著抑制了As由水稻地下部到地上部的转运以及地上部对As的吸收:扬稻6号地上部As含量为10.77mg·kg-1,显著低于农垦57(12.85mg·kg-1);扬稻6号对As的转移系数(TF)为0.067,仅为农垦57的73.6%.     

Influence of iron plaque on chromium accumulation and translocation in three rice (Oryza sativa L.) cultivars grown in solution culture

Hydroponic experiments were conducted to investigate the role of iron plaque on root surface in chromium accumulation and translocation in three rice cultivars (90-68-2, CDR22 and Jin 23A). Rice seedlings were grown under 1.0 mg L^?1 trivalent chromium (Cr(III)) stress with and without phosphorus (P) treatments. P addition significantly increased the shoot and root biomass in all three rice cultivars. In the absence of P, the amounts of iron plaque (DCB-extractable Fe) on the root surface increased resulting in the increase of Cr accumulation in iron plaque. Compared to that with P treatment, Cr concentrations in iron plaque without P treatment were enhanced by 2–3 folds in the three rice cultivars. There was a significantly positive correlation between DCB-extractable Cr and DCB-extractable Fe on the root surface of the three rice cultivars. There were no significant effects on Cr concentration in roots and shoots between P treatments, but significant differences among cultivars were observed. Cultivar Jin 23A had the lowest Cr concentration both in roots and shoots regardless of P treatment. The results suggest that iron plaque could be a trap for immobilising Cr from environment but may not affect Cr uptake and translocation. Screening and breeding the cultivars with low Cr accumulation is considered as the most effective approach in Cr contaminated areas.     

Dynamic changes in radial oxygen loss and iron plaque formation and their effects on Cd and As accumulation in rice (Oryza sativa L.)

Temporal variations and correlations between radial oxygen loss (ROL), iron (Fe) plaque formation, cadmium (Cd) and arsenic (As) accumulation were investigated in two rice cultivars at four different growth stages based upon soil pot and deoxygenated solution experiments. The results showed that there were significant differences in ROL (1.1–16 μmol O₂ plant^?1 h^?1), Fe plaque formation (4,097–36,056 mg kg^?1), Cd and As in root tissues (Cd 77–162 mg kg^?1; As 49–199 mg kg^?1) and Fe plaque (Cd 0.4–24 mg kg^?1; As 185–1,396 mg kg^?1) between these growth stages. ROL and Fe plaque increased dramatically from tillering to ear emergence stages and then were much reduced at the grain-filling stage. Furthermore, significantly positive correlations were detected between ROL and concentrations of Fe, Cd and As in Fe plaque. Our study indicates that increased Fe plaque forms on rice roots at the ear emergence stage due to the increased ROL. This stage could therefore be an important period to limit the transfer and distribution of Cd and As in rice plants when growing in soils contaminated with these toxic elements.     

The implications of planting mode on cadmium uptake and remobilization in rice: Field experiments across growth stages

•Direct seeding (DS) method led to more distributed Cd in aerial parts of rice. •The Cd content was significantly higher in brown rice with planting mode of DS. •Using DS lessened the Fe plaque covering the root surface in all growth stages. •Transplantation mode should be considered as a priority in Cd-contaminated areas. Global rice production practices have gradually changed from a reliance on transplanting to direct seeding. Yet how this shift may alter cadmium (Cd) accumulation in rice is poorly known. Here we conducted field experiments with two rice genotypes cultivars that were planted using three methods: via direct seeding (DS), seedling throwing (ST), and manual transplanting (MT). Rice samples were collected during four growth stages. The formation and distribution of iron plaque were analyzed using DCB (dithionite-citrate-bicarbonate) extractions and observed under micro-XRF (micro X-ray fluorescence). The results revealed that, in each growth stage, DS rice was more apt to harbor Cd distributed in the plant’s aerial parts, and the Cd concentration of brown rice from DS was 21.8%–43.3% significantly higher than those from ST and MT at maturity stage (p<0.05). During the vegetative stages, the Cd uptake percentage was higher in DS than MT rice, and those plants arising from the DS method were capable of absorbing more Cd earlier in their growth and development. Conversely, using DS decreased the amount of iron plaque covering the root surface in every growth stage, especially in the critical period of Cd accumulation, such that the roots’ middle areas were distinguished by a near-complete absence of iron plaque, thus weakening its role as an effective barrier to Cd uptake from soil. Collectively, this study demonstrated that implementing the DS mode of planting will increase Cd’s distribution in the aboveground parts of rice, and heightening the risk of Cd contamination in grain.     

Sequestration of As by iron plaque on the roots of three rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars in a low-P soil with or without P fertilizer

A pot experiment was carried out in a greenhouse to investigate the sequestration of As in iron plaques on root surface of three rice (Oryza sativa L.) cultivars. Phosphate (P) fertilization increased both plant biomass and tissue P concentrations significantly, indicating that the soils used in this study was highly P-deficient. Results from this study confirmed that low P supply improved the formation of iron plaque on rice roots. As a consequence, arsenic (As) concentrations in DCB-extracts with no P addition were significantly higher than those with P fertilization. Arsenic was highly sequestrated in iron plaque; arsenic concentration in iron was up to nearly 120 mg kg⁻¹, while arsenic concentrations in roots were just several mg kg⁻¹. Both arsenic and phosphate concentrations in iron plaque were highly positively correlated with the amounts of iron plaque (DCB-extractable Fe). Contrary to normal understanding that increasing P supply could reduced As accumulation in plants, results from the present study showed that P fertilization did not inhibit the As uptake by plants (As accumulation in aboveground), which was probably due to the fact that iron plaque formation was improved under low P conditions, thus leading to more As sequestration in the iron plaque. Thus results obtained in this study indicated that the iron plaque may inhibit the transfer of As from roots to shoots, and thus alter the P–As interaction in plant As uptake processes.     

砷胁迫下水磷耦合对不同磷效率水稻根表铁膜及其各部位砷含量的影响

为探索缓解水稻砷毒害的农艺措施,以耐低磷水稻99011和低磷敏感水稻99012为材料,通过土培试验,研究水分、磷用量及其交互作用对不同砷浓度酸性土壤中水稻根表铁膜以及植物体内砷分配的影响。结果表明,节水灌溉(干湿交替)明显减少水稻根表铁膜量,降低铁膜、根系、秸秆、颖壳和精米中的砷含量。与30mg·kg-1P2O5相比,180mg·kg-1P2O5能明显减少两个品种水稻的根表铁膜量以及根系和秸秆中的砷含量;对耐低磷品种铁膜砷含量影响不大,但显著降低磷敏感品种铁膜砷含量;在50mg·kg-1砷处理中增加磷用量对水稻颖壳砷含量影响不大,在100mg·kg-1砷处理时能显著降低颖壳砷含量;增加磷用量可明显增加耐低磷品种的精米砷含量,降低磷敏感品种的精米砷含量。水、磷交互效应主要受水分效应的影响。加砷处理后,相同处理下耐低磷品种的根表铁膜量和铁膜中的砷含量显著高于磷敏感品种,而根系、秸秆、颖壳和精米中的砷含量则相反。研究表明,可以通过节水灌溉,并根据砷污染程度和植物磷营养特性确定适当的磷肥用量,从而减少砷在水稻体内的累积,提高食品安全。