AGEING OF PHOSPHATE ADDED TO SOIL

The ageing of phosphate added to suspensions of a calcareous soil was measured in terms of the solubility of the phosphate and the amount of isotopically exchangeable phosphate (E value). These both showed a decrease in reactivity of the added phosphate during a period of 5 months. A constant ratio of E values after 24 and 500 hours showed that no redistribution within different fractions of labile phosphate occurred.     

铁营养状况及不同形态氮素对玉米体内不同铁库铁再利用的影响

采用分根技术、营养液培养方法 ,研究缺铁条件下供应不同形态氮素对玉米苗期体内不同铁库中铁再利用的影响。结果表明 ,缺铁条件下 ,玉米新生叶片铁营养状况不仅受体内铁库强度大小的影响 ,而且也受外界调节措施—氮素形态的调节。研究发现 ,与NO3-N相比 ,不考虑根细胞质外体铁库时 ,供应NH4-N可使初生叶中 32 %的铁再利用 ,考虑根系铁库时 ,初生叶铁变化不明显 ,而可使根系 40 %的铁转移至地上部。无论根系是否有铁库 ,缺铁条件下 ,NH4-N能提高新叶活性铁含量和伤流液中铁浓度。     

水稻长穗颈光温敏核不育系培矮64eS(1)的选育

用直接诱变获得eui基因突变的技术路线 ,成功地将目前生产上应用面积最大的光温敏核不育系培矮 64S改造为长穗颈培矮 64eS( 1 )。培矮 64eS( 1 )从遗传上解除了包穗 ,提高了培矮 64eS( 1 )的异交潜势 ,保持原培矮 64S的优良特性 ,可望达到建立不用或少用赤霉素的两系稻种子生产技术体系。利用其组配的杂种具增产趋势。     

DIFFERENTIAL TRANSLOCATION OF 59IRON IN IRON SUFFICIENT AND DEFICIENT SORGHUM PLANTS

Radioactively labeled iron (⁵⁹Fe) was used to study differential uptake in sorghum plants in the recovery stage of chlorosis. Radio-labeled ⁵⁹Fe was supplied through root feeding in nutrient solution experiment (48 hrs, pH 6.2) to non-chlorotic and chlorotic plants. Chlorotic plants were further treated with foliar spray [ferrous sulfate (FeSO₄), FeSO₄ + thiourea (TU), FeSO₄ + citric acid (CA), FeSO₄ + thioglycollic acid (TGA)] to study the uptake of radio-labeled ⁵⁹Fe through root feeding during recovery process of chlorosis. Under iron deficiency, the differential uptake of ⁵⁹Fe was markedly increased in leaves and stem of chlorotic control (-Fe) sorghum plants as compared to non-chlorotic control (+Fe) and foliar sprayed (FeSO₄, FeSO₄ + TU, FeSO₄ + CA, and FeSO₄ + TGA) plants. The lowest uptake of ⁵⁹Fe was observed in younger leaves (24.33 nmol, g^?1 fresh weight h^?1) and stem (1.98 nmol, g^?1 fresh weight h^?1) of non-chlorotic control followed by foliar sprayed plants in comparison to chlorotic control, respectively. Similarly less ⁵⁹Fe uptake was observed in the older leaves of FeSO₄ + CA sprayed (21.70 nmol, g^?1 fresh weight h^?1) plants in comparison to chlorotic control (35.60 nmol, g^?1 fresh weight h^?1). The highest differential ⁵⁹Fe uptake through nutrient medium was in the roots of plants, which were foliar sprayed with FeSO₄ along with TU. The role of iron alone and along with citric acid and thiol compounds is discussed in recovery of chlorosis.     

EVALUATION OF DIFFERENT IRON SOURCES FOR IRON CHLOROSIS RECOVERY IN LOW-CHILL PEACH CULTIVARS

An experiment was conducted with iron chlorosis affected low-chill peach cultivars such as ‘Shaharanpur Prabhat’, ‘Shan-e-Punjab’, and ‘Pratap’ to examine the recovery upon foliar application of three iron sources namely iron (Fe)-sulfate, Fe-citrate and Fe ethylenediaminetetraacetic acid (EDTA). All the iron sources significantly increased the SPAD meter value, physiologically active (Fe²⁺) iron and total iron content of the leaves over control. However, highest values were noted with foliar spray of 1.0% Fe-sulfate. The low-chill peach cultivar ‘Saharanpur Prabhat’ responded best with iron resupply treatment. Significant correlations (at P ≤ 0.01) were obtained between SPAD meter readings with both physiologically active iron (Fe²⁺) and total iron content of leaves in all peach cultivars. Among the sources, the correlations between SPAD meter readings, physiologically active iron (Fe²⁺) and total iron contents were significant at P ≤ 0.01 for only Fe-sulfate and Fe-citrate. The regression analysis showed that the SPAD meter reading accounted 78.2 to 88.0% variation in physiologically active iron (Fe²⁺) and 65.0 to 73.7% variation in the total iron content in the low-chill peach cultivars. The SPAD readings could be used for management of iron chlorosis in peach orchard.     

THE EFFECT OF IRON OXIDE IMPURITIES ON THE POSITIVE AND NEGATIVE ADSORPTION OF CHLORIDE BY KAOLINITES1

In the past, the effect of iron-oxide impurities in kaolinites has been ignored when studying properties such as edge-charge and Cl^? adsorption. In this investigation, iron oxides were found to have a marked effect on the adsorption of Cl^? by kaolinite. Cl^? was positively adsorbed by some kaolinites at high pH values indicating that positive charges were present under alkaline conditions. A large part of this positive adsorption of Cl^? was due to the iron oxide in the samples. The presence of small amounts of iron oxides gave rise to large errors in the measurement of edge-charge on kaolinite. After deferrification, reasonable results were obtained.     

FORMATION OF IRON OXIDES BY DECOMPOSITION OF IRON-PHENOLIC CHELATES

Iron chelates of some simple di-and trihydric phenols can be decomposed by peroxide treatment or by hydrolysis to yield crystalline ferric oxides. The species of ferric oxide obtained depends upon the precipitating conditions and the nature of the chelating ligand. In oxidative virtually anion-free conditions, decomposition of all aged chelates yields a precipitate of disordered ferric oxide, which is referred to as‘protohaematite’, since it ages to haematite in water even at room temperature. Protohaematite is considered to be a discrete form of ferric oxide similar in structure to δ-FeOOH but devoid of hydroxyl groups and may be present in freely drained soils as a precursor of haematite. Hydrolysis of all unaged chelates, except that of iron protocatechuic acid, yields lepidocrocite. The redox cycle undergone by iron in this reaction may be analogous to one prevailing in gley soils. In the presence of montmorillonite, the iron-catechol system forms a clay-metal-organic complex, which also decomposes to yield lepidocrocite provided chloride ions are present on the clay surface. The fact that various inorganic gels amorphous to X-rays can also deplete the ligand content of the chelates indicates a possible inorganic decomposition mechanism for metal-organic chelates in soils.     

土壤中氧化铁的转化及其对土壤结构的影响

氧化铁虽是土壤粘粒中的次要矿质成分,但它具有较高的活性,对土壤性质有重要的影响。作为胶结物质之一,氧化铁的形态及其含量,对土壤团聚体的形成,亦起重要作用^[4,8]。某些水稻土中细孔隙增多,土块趋向紧实等问题^[1,2],似乎与土壤中氧化铁存在形态有关。     

铁营养状况及不同形态氮素对玉米体内铁再利用效率影响的研究

本采用分根营养液培养方法,用＾５９Ｆｅ示踪技术研究了铁及不同形态氮素对玉米苗期体内铁再利用的影响。结果表明,缺铁促进了铁向地上部的运输,体内铁再利用率提高。与硝态氮相比,供庆铵态氮有利提高体内铁的再利用率,玉米新叶＾５９Ｆｅ含量比硝态氮处理的高９个百分点,改善了玉米新叶铁的营养状况。在缺铁条件下,供应铵态氮时、初生叶中＾５９Ｆｅ含量占地上部比例由５０％降至２５％,而供应硝态氮时,初生叶中该比值变     

利用~(14)示踪研究玉米/花生间作玉米根系分泌物对花生铁营养影响的机制

通过14 C示踪技术研究间作条件下玉米根系分泌物改善花生铁营养的作用。结果表明 ,玉米根系的分泌物可穿越尼龙网而到达间作花生的根际 ,同正常间作的花生一样 ,与单作相比 ,两种间作花生的铁营养状况得到了明显的改善 ,玉米光合作用固定的碳可通过根系分泌物进入花生根际并转移到花生的根系和地上部 ,玉米根系分泌物可活化土壤难溶性铁而提高土壤有效铁含量 ,这部分活化的铁可被花生吸收和利用     

THE MOBILIZATION OF IRON BY EXTRACTS OF EUCALYPTUS LEAF LITTER

When aqueous extracts of leaf litter from four closely related Eucalyptus species were reacted with soil material under aerobic conditions their iron mobilizing activity was found to be inversely related to the productivity of the sites on which the species grew. The activity of litter extracts of the four species grown in similar soils in the field was found to increase in the order E. regnans, E. obliqua, E. radiata, E. sieberiana. The results indicate that species-soil interactions could be as important as inherent species characteristics in determining whether or not a species is a ‘podzol former’. The effect on the activity of the extracts of altering their pH before reaction with either soil or with prepared iron oxides suggests that, whereas organic acids could be mainly responsible for mobilizing iron from soil and from anhydrous ferric oxide, polyphenols could be more important than organic acids in mobilizing iron from hydrous ferric oxide. The pH and E_h curves obtained when litter extracts were titrated with a ferric chloride solution showed that iron from this source was strongly reduced by the extracts at low pH.     

成都平原水稻土中铁的分异特点

本文研究了成都平原发育于岷江冲积物、紫色土沉积物和黄壤残积物三种不同母质的六个主要水稻土剖面中各种形态氧化铁含量及其在剖面中的分异特点,探讨了各种形态氧化铁之间的关系及其与环境条件、成土母质的关系。此外,根据全铁含量在剖面中的分异,讨论了发生层的形成。     

EFFECT OF BICARBONATE ON GROWTH AND IRON NUTRITION OF PEA

ABSTRACT

Two cultivars of pea with different sensitivity to bicarbonate (Merveille de Kelvedon, tolerant and PS210713, sensitive) were cultivated during one month on a nutrient solution containing or not bicarbonate (10 mM). The study indicated that bicarbonate increased the root to shoot ratio much more in the sensitive than in the tolerant one. Bicarbonate reduced iron translocation towards shoots of the two cultivars. This effect was more marked in the sensitive one. The study also showed that bicarbonate provoked a considerable accumulation of iron in roots of the two cultivars. This accumulation was due to iron accumulated in the extraplasm of roots.     

Kinetic Speciation of Ni(II) in Model Solutions and Freshwaters: Competition of Al(III) and Fe(III)

The competing ligand exchange method was used to investigate the competitive binding of Ni(II) by Al(III) and Fe(III) in model aqueous solutions and freshwaters. Graphite furnace atomic absorption spectrometry and adsorptive cathodic stripping voltammetry were used to monitor the rate of uptake of the Ni by Chelex 100 chelating resin and dimethylglyoxime as the competing ligands, respectively. The results have revealed that Ni(II)–humate complexes were more labile in presence of the mixture of Al(III) and Fe(III), compared to the lability of the Ni(II)–humate complexes when only one of the two, Al(III) or Fe(III), was present. The environmental significance of this work is that in model solutions simulating freshwater containing humic substances and the target trace metal Ni(II) and cations, Al(III) and Fe(III), the competitive binding of Ni(II), Al(III) and Fe(III) by humic substances makes Ni(II)–humate complexes labile, releasing free Ni²⁺–aqua complex, which reported to be toxic.     

Gallium(III) does not actively substitute for iron(III) in iron/gallium competition studies

Strategy II plants respond to Fe stress by releasing a phytosiderophore and are believed to absorb Fe as Fe(III). Gallium(III) has chemical characteristics which have made it useful as a substitute for Fe(III) in biological systems. The objectives of our study were to: 1) determine if Ga(III) acts competitively to reduce Fe(III) uptake or otherwise substitutes for Fe(III) in barley (Hordeum vulgare L.), and 2) determine if the competition for Fe(III) between EDDHA or BPDS and barley further elucidates the form of Fe absorbed by barley. Chlorosis ratings, phytosiderophore production, and tissue Fe contents were indexes of Fe stress.

Gallium was absorbed and translocated by the plant both in the presence and absence of Fe, and slightly alleviated Fe stress in the absence of Fe. However, Fe uptake was not affected by the presence of Ga. Thus, Ga(III) did not seem to compete with Fe(III) for uptake. Increasing EDDHA in solution intensified chlorosis and phytosiderophore production and reduced root Fe, but did not reduce leaf Fe concentration. Increased BPDS had no influence on either chlorosis or leaf Fe, but did cause phytosiderophore production to increase and root Fe to decline. The presence of Fe(II) in solutions containing BPDS suggests a potential for reducing Fe(III) in the roots of barley.     

Lactic acid decreases Fe(II) and Fe(III) retention but increases Fe(III) transepithelial transfer by Caco-2 cells

Lactic acid (LA) has been proposed to be an enhancer for dietary iron absorption, but contradictory results have also been reported. In the present study, fully differentiated Caco-2 cell monolayers were used to evaluate the effects of LA (1-50 mmol/L) on the cellular retention and transepithelial transport of soluble non-heme iron (as ferric nitrilotriacetate). Our data revealed a linear decline in Fe(III) retention with respect to the concentration of LA added. In the presence of 50 mmol/L LA, retention of Fe(III) and Fe(II) decreased 57% and 58%, respectively. In contrast, transfer of Fe(III) across the cell monolayer was doubled, while Fe(II) transfer across the cell monolayer decreased 35%. We conclude that LA reduces cellular retention and transepithelial transport of Fe(II) by Caco-2 cells in a dose-dependent manner. However, while LA also reduces retention of Fe(III) by Caco-2 cells, the transfer of Fe(III) across cell monolayers is enhanced, possibly due to effects on paracellular transport.     

SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDE BY EDTA FROM A MIXTURE OF AMORPHOUS IRON OXIDE, GOETHITE, AND HEMATITE

Iron (III) was extracted by EDTA and ammonium oxalate from a model substance consisting of amorphous iron oxide, goethite, and hematite precipitated in the presence of quartz sand. Even by varying the EDTA concentration between 0.02 and 0.1 M, pH between 4.40 and 6.00, the solid:solution ratio between I:25 and I:250, and using extraction times up to go days, it was found that EDTA was able to extract only a limited amount of iron. In contrast, 0.2 M ammonium oxalate at pH 3.0 is able to dissolve all the iron compounds if the extraction time is sufficient. Nevertheless, the amount of EDTA-extractable iron is equal to the amount of iron extracted after 4–5 hours with ammonium oxalateat pH 3.0. From X-ray analysis, DTA curves, a solubility product determination, and a kinetic investigation, it is concluded that the EDTA-extractable fraction consists of X-ray amorphous iron oxide, less soluble than polymeric iron hydroxide, and presumably only one compound. Therefore, it is concluded that it may be possible by means of EDTA to carry out a selective extraction of X-ray amorphous iron oxides mixed with goethite and hematite.