Effect Of Iron Plaque Research Articles

Effect of Iron Plaque on Gaseous Elemental Mercury Uptake, Translocation, and Volatilization by Paddy Rice.

Paddy rice is a typical wetland plant species, and mercury (Hg) accumulation in this rice has received much attention over the last two decades. The role of root iron plaque on rice Hg accumulation is not well understood. The effects of iron plaque on Hg0 uptake, translocation, and volatilization in rice seedlings were investigated under hydroponic conditions using different rice genotypes. After induction of iron plaque on rice roots with pretreatment solutions containing 0, 15 and 30mg Fe2+L-1, rice seedlings were transplanted into specially designed airtight culture chambers, where roots were separated from the aerial parts and exposed to saturated Hg0 vapor. The results showed the following: (1) There were significant differences in the amount of iron plaque formed on the rice roots among the three genotypes. (2) A significant correlation was observed between the concentrations of Hg and Fe in the iron plaque of the root surface for the three genotypes (R2 = 0.933, p < 0.01). (3) Iron plaque may act as a barrier for Hg0 behavior, i.e., inhibiting the process of Hg0 uptake and translocation from the rhizosphere.

Effects of iron plaque and fatty acids on the transfer of BDE-209 from soil to rice under iron mineral Fenton-like oxidation condition

To understand the effect mechanisms of iron plaque and fatty acids on the migration of PBDEs from soil to rice (Oryza sativa), pot experiments were conducted in the soil spiked with decabromodiphenyl ether (BDE-209) under the conditions of tourmaline and nano-goethite Fenton-like treatments. The results showed that iron mineral Fenton-like oxidation could effectively remove BDE-209 from rhizosphere soil, the highest removal rate obtained 89.29% with the addition of 0.4 mmol/L H2O2 and 8 g nano-goethite (G + 3H group). Iron mineral Fenton-like oxidation could produce iron plaque (IP) on rice roots and accumulate a part of contaminants on the surface of IP, further weakening BDE-209 uptake in the plants. Additionally, the occurrence of fatty acid variation induced by BDE-209 stress, iron mineral Fenton-like oxidation at high concentrations of H2O2 with 0.4 mmol/L affected the distribution of fatty acids in plant tissues, especially for C18:0 fatty acid. While the IP on rice roots prevented the BDE-209 into plant, it was also closely related to the distribution of fatty acids in rice, altering BDE-209 accumulation in the rice. To safely use the iron mineral Fenton-like oxidation in the agricultural soil remediation, the safety of plant cells treated by mineral Fenton-like oxidation was evaluated using the transmission electron microscopy (TEM) and enzyme activity determination, which indicated that iron mineral Fenton-like oxidation would destroy the inner structures of plant cells, especially for G + 3H group.

Effect of iron plaque on the root surface of hydrophyte on nitrogen and phosphorus transformation

Plants play an important role in constructed wetlands. However, the effect and mechanism in nutrient removal of iron plaque on the root surface were explained unclear. Because of the complexity of wetland system, this paper used hydroponics system to proceed the research. In this study, cattails were firstly cultured at 10% Hoagland's nutrient solution with 20 mg/L Fe2+ (Fe2+ as FeSO4·7H2O) for iron plaque formation, and then transplanted to growth chamber to examine the promoting effect and mechanism of pollutant removal. Compared with control groups without iron plaque, the average removal efficiency of COD, NH4+-N, NO3−-N and the total phosphorus (TP) improved significantly (P = 0.000 < 0.05). Iron plaque could enhance the related microbial processes and aerobic environment underwater, thus further facilitated pollutant removal. The results indicate that iron plaque on the root surface could enhance the removal performance of nitrogen and phosphorus in the aquatic environment.

Transformation and uptake of silver nanoparticles and silver ions in rice plant (Oryza sativa L.): the effect of iron plaque and dissolved iron

Iron plaque oxidized AgNPs and increased the uptake and translocation of silver by rice plant.

Could the rhizoplane biofilm of wetland plants lead to rhizospheric heavy metal precipitation and iron-sulfur cycle termination?

Iron plaque (IP) formation via radial oxygen loss (ROL) of wetland plant has been predominantly recognized as the reason for heavy metal sequestration in the rhizosphere. However, the same contribution of the microbes living in a potential rhizoplane biofilm matrix has not been comprehensively elucidated. In this review, we proposed a conceptional model of the wetland plant rhizoplane biofilm and summarized the possible pathways therein for heavy metal precipitation and iron-sulfur cycle termination. After an introduction of the effects of IP and microbes on the phytoremediation of heavy metal-contaminated wetland, the distribution of rhizospheric bacteria and different metal speciations resulted from wetland plant ROL were demonstrated. Based on the studies of microflora in the rhizosphere and IP, coupled with the ROL nature, we proposed an existence of rhizoplane biofilm with a special structure that could contribute to the rhizospheric iron-sulfur cycle termination by the production of heavy metal precipitates (metal sulfides). The ROL leads to the diffusion of oxygen with a decreasing gradient from the root surface (rhizoplane) to the bulk soil, allowing the formation of an unconventional rhizoplane biofilm comprising an aerobic inner layer and an anaerobic outer layer. Thus, aerobic bacteria, e.g., iron-oxidizing bacteria (IOB) and sulfur-oxidizing bacteria (SOB), as well as anaerobic bacteria, e.g., iron-reducing bacteria (IRB) and sulfate-reducing bacteria (SRB), are favored in the inner layer and outer layer of the rhizoplane biofilm, respectively. In the inner layer, ferrous sulfide is oxidized by IOB and SOB to Fe3+ and SO42−. Fe3+ is thereafter bound with oxygen into iron (hydro)oxides, aggregating into a barrier of iron plaque for heavy metal sequestration and O2 diffusion. Excessive SO42− diffused to the outer layer is reduced to S2− by SRB, forming sufficient metal sulfide precipitates that on one hand immobilize those heavy metal ions released by H+, and on the other hand serve as a barrier for preventing the contact of ferrous sulfide from O2. Hence, further oxidization of ferrous sulfide is terminated. This rhizoplane biofilm co-existing with IP contributes to the rhizosphere element circulation. Further investigation and demonstration of its composition, structure, and function will help us better interpret the survival strategy and bioremediation potential of wetland plants in flooded mining areas, such as mine tailing ponds in tropical and sub-tropical regions with abundant rainfall.

Iron plaque reduces cerium uptake and translocation in rice seedlings (Oryza sativa L.) exposed to CeO2 nanoparticles with different sizes

This study aims to assess the role of iron plaque (IP) on cerium (Ce) uptake and translocation by rice after CeO2 nanoparticles (NPs) exposure over a 4 days period. A hydroponic experiment was performed under two IP levels (low and high) combined with two CeO2 NPs size (14 nm and 25 nm). It was found that CeO2 NPs as the main form was absorbed by rice due to limited NPs dissolution in hydroponic solution. IP significantly reduced surface-Ce, root-Ce and shoot-Ce accumulation, irrespective of CeO2 NPs sizes. The reduced uptake of Ce was more obvious in NP25 than NP14. Ce accumulations decreased with increasing IP amounts. In IP treatments, the interactive attraction between NPs and root surface was weakened through the enhancement of hydrodynamic diameters and the reduction of ζ-potential of CeO2 NPs in solution, as well as the reduction of |ζ| values of rice root, which reduced the Ce bioaccumulation in rice. PCA indicated the negative correlation between surface-Ce (IP-C-Ce and IP-A-Ce) and NPs size, and between shoot-Ce/root-Ce and IP-Fe/tissue-Fe. IP also decreased Ce translocation from root to shoot. A full life study indicated the reduction effect of IP on surface-Ce, root-Ce, shoot-Ce and grain-Ce accumulations. These findings are significant as they imply that the IP formation is a promising approach for preventing Ce accumulation in rice, which would regulate Ce uptake by rice in the following growth stages and decrease the health risk of CeO2 NPs exposure in agricultural environment.

Formation of iron plaque in the roots of Spartina alterniflora and its effect on the immobilization of wastewater-borne pollutants

Iron plaque (IP) plays an important role in the absorption of heavy metals (HMs) and nutrients in wetland plants. The present study aims to investigate the effect of IP in Spartina alterniflora on the immobilization of wastewater borne HMs and nutrients. The physiological responses and effect of IP formation on the uptake of HMs, nitrogen (N), and phosphorus (P) were studied in S. alterniflora subjected to different synthetic wastewater (SW) levels and waterlogging durations. Results showed that IP formed in roots of S. alterniflora increased significantly with increasing SW concentration but decreased under prolonged waterlogging. Increasing the waterlogging time enhanced the alcohol dehydrogenase activity and the ethylene content in the roots of S. alterniflora. HMs including Cu, Pb, and Cr, did not significantly accumulate in the IP, despite that the IP content increased with the increasing of SW levels. The SEM–EDX analysis revealed that IP formed on the surface of S. alterniflora did absorb HMs such as Cu, Zn, and Cr. At a fixed level of SW, the amount of HMs that accumulated in the DCB extract was substantially proportional to the IP concentration in the root. Increasing of the SW level enhanced the accumulation of P in the leaves and roots of S. alterniflora. In conclusion, IP formed on S. alterniflora helped immobilize SW pollutants, including HMs and P, and the formation of IP and its effect on pollutant immobilization were influenced by the waterlogging conditions.

Iron plaque formation on wetland-plant roots accelerates removal of water-borne antibiotics

The effects of iron plaque on the removal of antibiotic or antifungal drugs, such as macrolides (MLs) and sorption mechanism are important for the selection of plants in constructed wetlands. We aim to evaluate the sorption of water-borne MLs by iron plaque on root surfaces of plants with different rates of radial oxygen loss (ROL). Aquatic sorption activity was determined in three wetland plant species, Canna indica, Juncus effusus and Iris pseudacorus) and four MLs, anhydroerythromycin A (ETM-H2O), roxithromycin (ROX), clarithromycin (CLA) and tilmicosin (TIL). The adsorption mechanism and iron plaque characteristics before/after adsorption were investigated. Roots of Juncus effusus removed more MLs than the other two plant species. This species with higher ROL also formed more iron plaques, which consequently adsorbed more MLs. MLs were largely immobilized by sorption onto the Fe (hydr)oxides formed. Multiple mechanisms included hydrophobic interaction, surface ionic exchange and surface complexation between the carbonyl group on the lactone ring of the ML and the ferric ions. Iron plaque enhances MLs removal by wetland plants. Selecting the dominant plant with high ROL can improve the formation of iron plaque on root surfaces and promote the removal of antibiotics in constructed wetlands.

The effect of iron plaque on lead translocation in soil-Carex cinerascens kukenth. system

A pot experiment was conducted to investigate the effect of iron plaque on Pb uptake by and translocation in Carex cinerascens Kukenth. grown under open-air conditions. Using Scanning Electron Microscopy and Energy Dispersive X-Ray Spectrometry, iron plaque was present as an amorphous coating on root surfaces with uneven distribution. The amount of iron plaque increased significantly with increasing Fe additions regardless of Pb additions. The presence of iron plaque on the root surface of Carex cinerascens Kukenth. increased the concentrations of Pb adsorbed by iron plaque. The Pb percentage in whole roots increased by 14.52% at 500 mg kg−1 Fe treatment than at 0 mg kg−1 Fe, and the distribution coefficient (DC) of Pb and translocation factor (TF) root increased with Fe additions, but translocation factor (TF) shoot decreased with Fe additions. The results suggested that iron plaque could promote the translocation of Pb from soil to roots to some extent, and it played a role to reduce heavy metals pollution of Poyang Lake wetland.

Effect of iron plaque on antimony uptake by rice (Oryza sativa L.)

Although iron (Fe) plaque has been shown to significantly affect the uptake of toxic antimony (Sb) by rice, knowledge about the influence of iron plaque on antimony (Sb) (amount, mechanisms, etc) is, however, limited. Here, the effect of Fe plaque on Sb(III) and Sb(V) (nominal oxidation states) uptake by rice (Oryza sativa L.) was investigated using hydroponic experiments and synchrotron-based techniques. The results showed that iron plaque immobilized Sb on the surface of rice roots. Although the binding capacity of iron plaque for Sb(III) was markedly greater than that for Sb(V), significantly more Sb(III) was taken up by roots and transported to shoots. In the presence of Fe plaque, Sb uptake into rice roots was significantly reduced, especially for Sb(III). However, this did not translate into decreasing Sb concentrations in rice shoots and even increased shoot Sb concentrations during high Fe–Sb(III) treatment.

Interaction between iron plaque and root border cells ameliorates aluminum toxicity of Oryza sativa differing in aluminum tolerance

Root border cells (RBCs), which are generated during plant growth and surround the root cap, and iron plaque (IP), ubiquitously formed on the root surfaces of rice, are known to alleviate aluminum (Al) toxicity. To verify the interactive effects of IP and RBCs on ameliorating Al toxicity, two rice cultivars differing in Al resistance were used to compare Al tolerance between cultivars. Additionally, root elongation, Al uptake and RBCs viability were measured as indicators of the effects of Al. The amounts of DCB-extractable Fe and Al on the root surfaces were much higher in the presence of IP than the absence. IP presence significantly decreased Al-induced inhibition of root elongation and Al contents in roots and root tips. The removal of RBCs from the root tips caused a more severe inhibition of root elongation and a higher Al accumulation in rice roots and root tips. Furthermore, root growth inhibition and Al contents in roots and root tips were significantly lower in roots with a combination of IP and RBCs than in roots with IP or RBCs only. The formation of IP on the root surface maintained higher RBCs viability and depressed mucilage exudation in an Al-tolerant rice cultivar. The results suggest that both IP and RBCs ameliorate Al toxicity, and IP has a greater capacity for Al resistance. The combination of IP and RBCs exhibited a synergistic effect associated with Al resistance.

Effects of iron plaque on phosphorus uptake by Pilea cadierei cultured in constructed wetland

Iron plaque often forms in the root surfaces of aquatic and terrestrial plant species. However, little is known about the role of iron plaque in controlling phosphate (P) movement from soil or water to the aboveground part of a wetland plant. This study, based on a constructed wetland model system, systematically investigat-ed the influence of iron plaque on phosphorus uptake by and accumulation in a typical wetland plant named as Pilea cadierei. Plants were treated with Fe and P at a loading rate of 0,500 or 1000 mg Fe kg−1 soil and 0, 5, 10, 50 or 100 mg P L−1 simulated waste water. Study results demonstrated iron plaque on the root surface is not a barrier to P uptake & translocation within Pilea cadierei, and iron plaque concentrations in Dithionite-Citrate-Bicarbonate (DCB) extracts were significantly affected by the input level of P and Fe. Moreover, the P concentration in DCB-extracts and in roots and shoots were also significantly affected by the input level of P and Fe. Higher loading level of Fe and P renders iron plaque a higher capacity to adsorb phosphorus.

Influence of iron plaque on accumulation of lead by yellow flag (Iris pseudacorus L.) grown in artificial Pb-contaminated soil

Purpose The relationship between plant absorption and accumulation of heavy metals and the effect of iron plaque on roots of wetland plants are unknown, especially for plants grown in heavy metal-contaminated soil. This experiment was designed to study the effects of iron addition on the formation of iron plaque in the rhizosphere of the wetland plant species Iris pseudacorus L. in artificial Pb-contaminated soil and the effects of iron plaque on Pb accumulation by plants.

The effects of iron plaque and phosphorus on yield and arsenic accumulation in rice

The effects of arsenate, Fe2+, and phosphate on amount and composition of Fe-oxide plaque at the rice-root surface and on the yield and arsenic accumulation in rice (cv. BRRI dhan33) were studied in a replicated pot-culture experiment. Arsenic in the form of Na2HAsO4 was applied at concentrations of 0, 15 and 30 mg kg−1 in combination with P and/or Fe at 0 and 50 mg kg−1, from KH2PO4 and FeSO4, respectively. Root, grain and straw yields and their As, Fe and P concentrations were determined. The Fe-oxide plaque was extracted from the plant roots using dithionite-citrate-bicarbonate (DCB) and NH4-oxalate extractions. The addition of Fe2+ reduced the toxic effect of As in flooded-rice culture and resulted in reduced grain-As accumulation and increased grain yields. The effect of applied phosphate was the opposite, in that it resulted in higher As concentrations in both grain and straw and lower grain yields. The effects of both Fe and P can be explained based on their impacts on adsorption of As onto soil and rice-plaque Fe-oxides and the subsequent As solubility and availability for uptake by rice. These reactions have important implications to rice-crop management and the natural variability in soils and irrigation-water characteristics that might impact As uptake by rice.

Arsenate uptake and translocation in seedlings of two genotypes of rice is affected by external phosphate concentrations

Two genotypes of rice ( Oryza sativa L.), 94D-54 and 94D-64 were used to investigate the formation of iron plaque controlled by different phosphorus (P) concentrations and the effect of iron plaque on arsenate uptake in a hydroponic experiment. External P concentrations from 10 to 50 μM caused a marked decrease in dithionite-citrate-bicarbonate (DCB)–Fe concentrations for both genotypes, but further increases from 50 to 300 μM only resulted in small decrease. Arsenic (As) concentrations in DCB-extracts were determined by the amounts of iron plaque and the adsorption capacity of As by iron plaque, and both controlled by external P concentrations. At 10 μM external P, genotype 94D-54 had higher Fe, As and P concentrations in DCB-extracts than genotype 94D-64, but the difference disappeared with increasing P concentrations. Increasing P concentrations decreased the percentages of As distributed in iron plaque from around 70 to 10%, and increased the percentages of As in roots and shoots gradually from around 20 to 60% for toots and from 5 to nearly 35% for shoots, respectively. Moreover, P concentration increased the molar ratio of shoot-to-root As, from 0.05 to nearly 0.2, indicating P concentration may promote As translocation from roots to shoots.

Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.): Phosphorus uptake

Under anaerobic conditions, ferric hydroxide deposits on the surface of rice roots have been shown to affect the uptake of some nutrients. In the present experiment, different amount of this iron plaque were induced on the roots of rice (Oryza sativa L. cv. TZ88-145) by supplying different Fe(OH)3 concentrations in nutrient solutions, and the effect of the iron plaque on phosphorus uptake was investigated. Results showed that 1) iron plaque adsorbed phosphorus from the growth medium, and that the amount of phosphorus adsorbed by the plaque was correlated with the amount of plaque; 2) the phosphorus concentration in the shoot increased by up to 72% after 72 h at concentration of Fe(OH)3 in the nutrient solution from 0 to 30 mg Fe/L, corresponding with amounts of iron plaque from 0.2 to 24.5 mg g-1 (root d. wt); 3) the phosphorus concentration in the shoots of rice with iron plaque was higher than that without iron plaque though the concentration in the shoot decreased when Fe(OH)3 was added at 50 mg Fe/L producing 28.3 mg g-1 (root d. wt) of plaque; and 4) the phosphorus concentrations in Fe-deficient and Fe-sufficient rice plants with iron plaque were the same, although phytosiderophores were released from the Fe-deficient roots. The phytosiderophores evidently did not mobilise phosphorus adsorbed on plaque. The results suggest that iron plaque on rice plant roots might be considered a phosphorus reservoir.

Zinc, lead and cadmium accumulation and tolerance in Typha latifolia as affected by iron plaque on the root surface

The effects of iron plaque on the growth of Typha latifolia L. and its accumulation of zinc (Zn), lead (Pb) and cadmium (Cd) were investigated under field conditions and in nutrient solution cultures in the laboratory. In the field, Zn concentrations (but not Cd) on the root surface were positively related to Fe concentrations on the root surface. In the laboratory, seedlings with and without iron plaque on their roots were exposed to 2.0 and 1.0 μg ml −1 Zn for 3 and 72 days and to 10.0 μg ml −1 Pb and 0.2 μg ml −1 Cd for 48 days. Zn accumulation was similar in seedlings with and without plaque when exposed to 2.0 μg ml −1 Zn for 3 days. Over the longer growth periods there was no significant difference in root and shoot dry weights when seedlings with and without plaque were treated with control or metal solutions. Root lengths both in the control and the Cd solution were significantly shorter in seedlings with plaque than in those without. Zn was absorbed fairly equally on root surfaces with and without plaque; however, roots with plaque absorbed more Pb, but less Cd, than those without. The presence of plaque did not alter Zn, Pb and Cd translocation in seedlings in the nutrient solutions. Most of the Pb and Cd taken up was retained in the roots, whereas most of the Zn taken up was retained in the shoots, suggesting that root tissue rather than the root surface or plaque is the main barrier for Pb and Cd transport. However, plaque may act as an effective Fe reservoir to increase Fe ion concentrations in active cells and then ameliorate metal toxicity.

Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.). Zinc uptake by Fe-deficient rice

This solution culture study examined the effect of the deposition of iron plaque on zinc uptake by Fe-deficient rice plants. Different amounts of iron plaque were induced by adding Fe(OH)3 at 0, 10, 20, 30, and 50 mg Fe/L in the nutrient solution. After 24 h of growth, the amount of iron plaque was correlated positively with the Fe(OH)3 addition to the nutrient solution. Increasing iron plaque up to 12.1 g/kg root dry weight increased zinc concentration in shoots by 42% compared to that at 0.16 g/kg root dry weight. Increasing the amount of iron plaque further decreased zinc concentration. When the amounts of iron plaque reached 24.9 g/kg root dry weight, zinc concentration in shoots was lower than that in shoots without iron plaque, implying that the plaque became a barrier for zinc uptake. While rice plants were pre-cultured in −Fe and +Fe nutrient solution in order to produce the Fe-deficient and Fe-sufficient plants and then Fe(OH)3 was added at 20, 30, and 50 mg Fe/L in nutrient solution, zinc concentrations in shoots of Fe-deficient plants were 54, 48, and 43 mg/kg, respectively, in contrast to 32, 35, and 40 mg/kg zinc in shoots of Fe-sufficient rice plants. Furthermore, Fe(OH)3 addition at 20 mg Fe/L and increasing zinc concentration from 0.065 to 0.65 mg Zn/L in nutrient solution increased zinc uptake more in Fe-deficient plants than in Fe-sufficient plant. The results suggested that root exudates of Fe-deficient plants, especially phytosiderophores, could enhance zinc uptake by rice plants with iron plaque up to a particular amount of Fe.

Copper and nickel uptake, accumulation and tolerance in Typha latifolia with and without iron plaque on the root surface

The effects of iron plaque on the growth of Typha latifolia L. and accumulation of copper and nickel in T. latifolia were investigated under laboratory conditions in nutrient solution cultures. Seedlings with and without iron plaque on their roots were exposed to 0.05 μg ml-1 Cu and 0.10 μg ml-1 Ni solutions for 72 d. The results showed no differences in root and shoot d. wt and leaf elongation when Cu or Ni were added to the solution and in the presence or absence of plaque. However, root length was reduced by Cu and Ni, and the reduction in root length was greater in the presence of plaque. Some Cu and Ni was adsorbed on root surfaces; roots with plaque took up more Cu, but less Ni than those without. The presence of plaque did not alter Cu uptake and translocation but increased Ni uptake and translocation. Most of the Cu and Ni taken up was retained in the roots, suggesting that the root tissue rather than the root surface or plaque is the main barrier for Cu and Ni transport. The results differ from those reported for other species.

Effect of iron plaque on roots of rice on growth of plants in excess zinc and accumulation of phosphorus in plants in excess copper or nickel

Abstract Iron (Fe) plaque on roots of rice was found to lessen the toxic effects of zinc (Zn). With excess Zn, plants with Fe plaque had significantly greater dry mass of roots and foliage than plants without plaque. In the excess of Zn, plants with Fe plaque had higher concentrations of Fe but lower Zn than plants without plaque, although the differences were not significant. In the excess of copper (Cu) or nickel (Ni), plants with Fe plaque had significantly lower concentration of phosphorus (P) in leaves than plants without plaque. It is suggested that the low concentration of P in leaves of plants with plaque will increase the concentration of “active iron”; inside leaves, and therefore, increase their tolerance against heavy metal toxicity.