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1.
Mechanism of Fe uptake by the leaf symplast: Is Fe inactivation in leaf a cause of Fe deficiency chlorosis? 总被引:5,自引:0,他引:5
The mechanism of iron (Fe) uptake from the leaf apoplast into leaf mesophyll cells was studied to evaluate the putative Fe
inactivation as a possible cause of Fe deficiency chlorosis. For this purpose, sunflower (Helianthus annuus L.) and faba bean
plants (Vicia faba L.) were precultured with varied Fe and bicarbonate (HCO
3
-
) supply in nutrient solution. After 2–3 weeks preculture, FeIII reduction and 59Fe uptake by leaf discs were measured in solutions with Fe supplied as citrate or synthetic chelates in darkness. The data
clearly indicate that FeIII reduction is a prerequisite for Fe uptake into leaf cells and that the Fe nutritional status of plants does not affect either
process. In addition, varied supply of Fe and HCO
3
-
to the root medium during preculture had no effect on pH of the xylem sap and leaf apoplastic fluid. A varied pH of the incubation
solution had no significant effect on FeIII reduction and Fe uptake by leaf discs in the physiologically relevant pH range of 5.0–6.0 as measured in the apoplastic leaf
fluid. It is concluded that Fe inactivation in the leaf apoplast is not a primary cause of Fe deficiency chlorosis induced
by bicarbonate.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Iron Enhances Aluminum-induced Leaf Necrosis and Plant Growth Inhibition in Eucalyptus camaldulensis
The combined effects of excess Fe and Al on Eucalyptus camaldulensis Dehnh. were studied by investigating time course and visible symptoms of leaf necrosis, plant biomass, the status of some
antioxidants and pigments and nutrient concentrations. Seedlings were grown hydroponically in nutrient solutions containing
0 or 500 μM AlCl3, each with a FeSO4 range of 1, 12 and 120 μM at pH 4.2. Leaf necrosis and plant growth inhibition were induced by Al and enhanced by the increase in Fe concentration.
The process from the first appearance of necrotic spots to leaf death (shedding) of a leaf proceeded from a few days to about
20 days after the leaf had fully expanded. Either 120 μM Fe without Al or Al reduced plant growth to a similar extent but 120 μM Fe without Al did not cause leaf necrosis. In leaves, excess Fe (12 and 120 μM) without Al reduced concentration of ASC and GSH, while concentration of Fe, DHA and GSSG and DHA:ASC and GSSG:GSH ratios
tended to increase with the increase in Fe concentration in treatment solution with or without Al. At 1 μM Fe, Al increased concentration of DHA and DHA:ASC and GSSG:GSH ratios. Catalase activity in leaves reduced with the increase
in leaf Al concentration. At 1 μM Fe, Al greatly reduced concentrations of Fe and chlorophylls in leaves but increase two times Fe concentration in stems.
These suggest that the enhancement effects of Fe on Al-induced leaf necrosis and plant growth inhibition can be discussed
in context of the excess Fe itself weakens antioxidant capability of ASC–GSH cycle in leaves and greatly reduces plant growth;
and the increase in Fe accumulation in stems is involved in Al-induced leaf chlorosis. 相似文献
3.
A study has been made on the effect of primary leaves on iron (Fe) distribution in the shoot. Bean (Phaseolus vulgaris L.) seedlings were precultured in nutrient solution with 8×10-5
M FeEDTA for 4 days, and then grown further with either 8×10-5
M FeEDTA (+Fe) or without Fe supply (-Fe) for another 5 days. Thereafter, both +Fe and -Fe plants were treated in three different ways: undisturbed; one primary leaf removed; or one primary leaf shaded, starting two hours before supply 59FeEDTA to the roots. The +Fe plants were supplied with 8×10-5
M
59FeEDTA, and the -Fe plants with only 1×10-6
M
59FeEDTA. After 1 to 8 hour uptake periods, plants were harvested and 59Fe in different organs was determined. Removal or shading of one primary leaf did not affect 59Fe uptake by roots and 59Fe translocation to the shoot in +Fe plants. In the -Fe plants, however, removal of one primary leaf decreased 59Fe uptake by roots, whereas shading of one primary leaf had no effect on 59Fe uptake but slightly enhanced 59Fe translocation from roots to the shoot. The quantity of 59Fe in primary leaves was positively correlated with quantity of 59Fe in the stem in the -Fepplants, but not in the +Fe plants. In both, the +Fe and -Fe plants, the quantity of 59Fe in the shoot apex was positively correlated with 59Fe in primary leaves. The results suggest that irrespective of the Fe nutritional status of plants, the source of Fe for the shoot apex is Fe retranslocated from primary leaves. 相似文献
4.
Iron supply to tobacco plants through foliar application of iron citrate and ferric dimerum acid 总被引:2,自引:0,他引:2
Experiments to assess the re-greening and the distribution of leaf-applied iron (Fe) within the aerial organs were developed with tobacco ( Nicotiana tabacum L.) plants. Fe (III)-citrate and Fe-dimerum acid were applied to a part of the leaf and plant re-greening was monitored for 6 weeks after treatment. Fluid Fe increments associated with foliar Fe application were measured within 3 days after application. Fe distribution from the site of application within the leaf and the untreated above-ground plant parts was evaluated. Leaf fluid Fe concentration was determined by a novel procedure based on Fe chelation by desferrioxamine E and high performance liquid chromatography separation on a reversed-phase column. The ferrioxamine E method enabled accurate determination of small amounts of Fe present in leaf fluid. Foliar Fe-dimerum acid and Fe (III)-citrate treatment to chlorotic tobacco plants induced new growth re-greening. It was concluded that the applied Fe-containing compounds penetrated the leaf, were distributed within the plant and that Fe supplied as both complexes could be utilized by the plant cell. 相似文献
5.
为探究柠檬酸或EDTA-Na_2对Pb污染下黑麦草(Lolium perenne L.)吸收Pb和营养元素特性的影响,对水培黑麦草进行不同处理,研究黑麦草一些生理生化指标的变化。结果表明,与对照相比,Pb处理降低黑麦草干重,增加质膜透性和根系脱氢酶活性,且在叶和根中积累Pb,而叶和根中6种营养元素含量的变化不尽相同。与Pb处理同时加入低浓度的柠檬酸或EDTA-Na_2对其生长影响较小,且叶片的Pb积累量较低;而同时加入高浓度的柠檬酸或EDTA-Na_2,虽然强化Pb在叶片中的积累,但是加重了生长的抑制作用和营养元素的稳态失衡;1 mmol L~(–1)的柠檬酸强化叶片积累Pb的效应强于同浓度的EDTA-Na_2,而5和10 mmol L~(–1)柠檬酸的强化作用则弱于同浓度的EDTA-Na_2。因此,适当浓度的柠檬酸或EDTA-Na_2在治理Pb污染环境中具有一定作用。 相似文献
6.
以羊草幼苗为研究对象,通过调整全营养培养基(CK,0.05 mmol/L Fe2+、0.015 mmol/L Zn2+)中铁或者锌含量设置0、10倍、20倍Fe2+(Zn2+)浓度处理Fe0(Zn0)、Fe10(Zn10)、Fe20(Zn20),以及在高铁培养基中单独添加0.15 mmol/L Zn2+或同时添加10 mmol/L Ca2+、5 mmol/L Mg2+、20 mmol/L K+处理,测定培养6 d后幼苗生长指标和矿质元素含量、以及高铁(Fe20)处理下幼苗根中抗氧化指标和相关基因表达量,探究不同浓度Fe2+、Zn2+对羊草幼苗生长、矿质元素吸收积累及抗氧化指标、基因表达的影响。结果表明:(1)缺锌(Zn0)显著抑制羊草幼苗鲜重的增加和Zn元素的积累,但促进Fe、Mg元素的积累;高浓度锌(Zn10、Zn20)显著促进幼苗叶片生长和Zn元素的积累;缺铁(Fe0)显著抑制幼苗的根长、鲜重和Fe元素的积累,促进Mg、Zn元素的积累;高浓度铁(Fe10、Fe20)显著抑制羊草幼苗根叶生长、根毛发育和Ca、Zn、Mg、K元素的积累。(2)增加Zn2+和Ca2+、Mg2+、K+浓度无法恢复高铁胁迫对幼苗生长的抑制作用。(3)高浓度铁(Fe20)处理羊草幼苗48 h后,根部过氧化物酶、超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶活性和丙二醛、抗坏血酸、还原型谷胱甘肽含量显著升高;烟酰胺合成酶基因、过氧化物酶基因表达量显著下调,植物类萌发素蛋白基因表达量显著上调。研究发现,羊草幼苗生长发育和矿质元素积累对环境中Zn2+浓度变化不敏感,却受到环境中高浓度Fe2+的显著抑制,并造成严重的氧化胁迫伤害,这种伤害无法在添加Zn2+或同时添加Ca2+、Mg2+、K+的条件下恢复。 相似文献
7.
Impact of nitrogen form on iron uptake and distribution in maize seedlings in solution culture 总被引:6,自引:0,他引:6
Comparative studies on the effect of nitrogen (N) form on iron (Fe) uptake and distribution in maize (Zea mays L. cv Yellow 417) were carried out through three related experiments with different pretreatments. Experiment 1: plants were precultured in nutrient solution with 1.0×10–4 M FeEDTA for 6 d and then exposed to NO3–N or NH4–N solution with 1.0×10–4 M FeEDTA or without for 7 d. Experiment 2: plants were precultured with 59FeEDTA for 6 d and were then transferred to the solution with different N forms, and 0 and 1.0×10–4 M FeEDTA for 8 d. Experiment 3: half of roots were supplied with 59FeEDTA for 5 d and then cut off, with further culturing in treatment concentrations for 7 d. In comparison to the NH4-fed plants, young leaves of the NO3-fed plants showed severe chlorosis under Fe deficiency. Nitrate supply caused Fe accumulation in roots, while NH4–N supply resulted in a higher Fe concentration in young leaves and a lower Fe concentration in roots. HCl-extractable (active) Fe was a good indicator reflecting Fe nutrition status in maize plants. Compared with NO3-fed plants, a higher proportion of 59Fe was observed in young leaves of the Fe-deficient plants fed with NH4–N. Ammonium supply greatly improved 59Fe retranslocation from primary leaves and stem to young leaves. Under Fe deficiency, about 25% of Fe in primary leaves of the NH4-fed plants was mobilized and retranslocated to young leaves. Exogenous Fe supply decreased the efficiency of such 59Fe retranslocation. The results suggest that Fe can be remobilized from old to young tissues in maize plants but the remobilization depends on the form of N supply as well as supply of exogenous Fe. 相似文献
8.
A. Álvarez-Fernández P. García-Laviña C. Fidalgo J. Abadía A. Abadía 《Plant and Soil》2004,263(1):5-15
The effectiveness of foliar fertilization to re-green chlorotic leaves in iron-deficient pear trees has been studied. Trials were made to assess the influence of (i) the level of Fe deficiency, (ii) the leaf surface treated (adaxial or abaxial), and (iii) two different surfactants, L-77 and Mistol. Treatments were ferrous sulphate alone, ascorbic, citric and sulphuric acids, applied either alone or in combination with ferrous sulphate, Fe-DTPA and water as a control. Solutions were applied with a brush and leaves were treated twice each year. None of the treatments caused a full recovery from Fe deficiency chlorosis. Treatments containing Fe caused the largest re-greening effects, and FeSO4 had a similar re-greening effect to Fe(III)-DTPA. Increases in leaf Chl were more pronounced with abaxial leaf surface applications and in severely deficient leaves. Using Fe(III)-DTPA in foliar sprays does not seem to be justified, since their effects are not better than those of FeSO4. The joint use of Fe(III)-DTPA and L-77 and that of FeSO4 and citric acid do not seem to be suitable. With a single foliar application, FeSO4 combined with acids gave slightly better results than FeSO4 alone. Acidic solution applications without Fe may be effective in alleviating chlorosis in some cases, especially in the case of citric acid. In the current state of knowledge, foliar fertilization cannot offer yet a good alternative for full control of Fe chlorosis, although its low environmental impact and cost make this technique a good complementary measure to soil Fe-chelate applications and other chlorosis alleviation management techniques.
Abbreviations: Chl – chlorophyll; EDDCHA – ethylenediamine di(5-carboxy-2-hydroxyphenylacetic) acid; EDDHA – ethylenediamine di(o-hydroxyphenylacetic) acid; EDDHMA – ethylenediamine di(o-hydroxy-p-methylphenylacetic) acid; EDDHSA – ethylenediamine di(2-hydroxy-5-sulfophenylacetic) acid 相似文献
9.
Iron uptake from ferrated (59Fe) pseudobactin (PSB), a Pseudomonas putida siderophore, by various plant species was studied in nutrient solution culture under short term (10 h) and long term (3 weeks) conditions. In the short term experiments, 59Fe uptake rate from 59FePSB by dicots (peanuts, cotton and sunflower) was relatively low when compared with 59Fe uptake rate from 59FeEDDHA. Iron uptake rate from 59FePSB was pH and concentration dependent, as was the Fe uptake rate from 59FeEDDHA. The rate was about 10 times lower than that of Fe uptake from the synthetic chelate. Results were similar for long term experiments.Monocots (sorghum) in short term experiments exhibited significantly higher uptake rate of Fe from FePSB than from FeEDDHA. In long term experiments, FePSB was less efficient than FeEDDHA as an Fe source for sorghum at pH 6, but the same levels of leaf chlorophyll concentration were obtained at pH 7.3.Fe uptake rates by dicots from the siderophore and FeEDDHA were found to correlate with Fe reduction rates and reduction potentials (E0) of both chelates. Therefore, it is suggested that the reduction mechanism governs the Fe uptake process from PSB by dicots. Further studies will be conducted to determine the role of pH in Fe aquisition from PSB by monocots. 相似文献
10.
Dr. Jaime M. Tapia Jesús Muñoz Felisa González Maria L. Blázquez Antonio Ballester 《Preparative biochemistry & biotechnology》2013,43(8):815-827
The sorption of Fe(II) and Fe(III) by extracellular polymeric substances (EPS) of acidophilic bacteria Acidiphilium 3.2Sup(5) and Acidithiobacillus ferrooxidans, harvested from the ecosystem of the Tinto River (Huelva, Spain), was investigated. EPS from mixed cultures of both bacteria (EPSmixed) and pure cultures of A. 3.2Sup(5) (EPSpure) were extracted with ethylenediamine tetraacetic acid (EDTA) and were characterized by Fourier-transform infrared (FTIR), electron photoemission (XPS), x-ray diffraction (DRX), and energy dispersive x-ray (EDX) spectroscopy and scanning electron microscopy (SEM). EPS pure were loaded, in sorption tests, with Fe(II) and Fe(III). The results obtained indicate that the biochemical composition and structure of EPSmixed was very similar to that of EPSpure. Besides, results indicate that EPSmixed adsorbed Fe(II) and Fe(III) by preferential interaction with the carboxyl group, which favored the formation of Fe(II)/Fe(III) oxalates. These species were also formed in EPSpure loaded with Fe(II)/Fe(III). All this behavior suggested that the sorption of iron by EPSmixed was similar to sorption of EPSpure, which fitted the Freundlich model. Thus, the iron uptake of EPSmixed reached 516.7 ± 23.4 mg Fe/g-EPS at an initial concentration of 2.0 g/L of Fetotal and Fe(II)/Fe(III) ratio of 1.0. 相似文献
11.
C. O. Ajakaiya 《Plant and Soil》1986,94(2):235-245
Summary Cowpea, (Vigna unguiculata L.) was grown using 3 soil types (designated Black, Red and Calcareous) at 4 rates of P (0, 40, 80 and 160 kg/ha) and 4 rates
of Fe (0, 2, 4, and 8 kg/ha). Sampling was done fortnightly (starting at 4 weeks after planting) for measurements of leaf
area, plant height, leaf dry weight and leaf concentrations of P and Fe.
Cowpea plants on Po treatment were stunted, irrespective of soil type. The P requirement for good growth on the Black soil was only a quarter
that on the other two soils.
Different P−Fe ratios (24∶1, 17∶1 and 12∶1) were required for best cowpea growth on the Black Red and Calcareous soils respectively.
Significant (P=0.05) increases in growth were obtained with the addition of P while addition of Fe did not lead to any such significant
increases in growth on any of the 3 soils.
Highest leaf P was obtained in plants grown on the Black soil while the lowest was in plants on the Calcareous soil. 相似文献
12.
Changes in iron availability in Arabidopsis are rapidly sensed in the leaf vasculature and impaired sensing leads to opposite transcriptional programs in leaves and roots 总被引:1,自引:0,他引:1
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Mather A. Khan Norma A. Castro‐Guerrero Samuel A. McInturf Nga T. Nguyen Ashley N. Dame Jiaojiao Wang Rebecca K. Bindbeutel Trupti Joshi Silvia S. Jurisson Dmitri A. Nusinow David G. Mendoza‐Cozatl 《Plant, cell & environment》2018,41(10):2263-2276
13.
Mark Farrell John R. Healey Douglas L. Godbold Mark A. Nason Susan Tandy Davey L. Jones 《Restoration Ecology》2011,19(4):509-519
Use of composts for habitat restoration offers advantages in terms of efficient use of resources. Chemical amendment of compost to reduce its pH and P availability was investigated in order to improve suitability for use in reclamation of blocky quarry waste to acidic grassy heathland. The effect of these amendments was observed on competition between two grass species: Agrostis capillaris and Festuca ovina. A factorial, pot‐scale greenhouse experiment was set up using two composts (one a mixture of green waste and catering waste, and the other a mixture of green waste and sewage sludge). In addition, two soils were collected from upland acidic grassland to provide a natural comparison. S0 was applied to reduce soil pH, and Fe(OH)3 from a coal waste treatment plant was applied to counteract the expected increase in P availability due to acidification of the composts by S0. Addition of S0 significantly reduced soil solution pH and addition of Fe(OH)3 significantly reduced soil solution P concentration. In one compost S0 reduced the biomass of F. ovina while increasing that of A. capillaris, whereas Fe(OH)3 had no significant effect on the biomass of either species. Although S0 and Fe(OH)3 did adjust the chemical properties of the soil solution, Fe(OH)3 did not bind P strongly enough to make it unavailable to plants. Further work is required, however, the use of chemically amended composts provides a sustainable sink for organic wastes and we conclude from this study that they have great potential for large‐scale restoration of blocky waste tips. 相似文献
14.
Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.). Zinc uptake by Fe-deficient rice 总被引:6,自引:0,他引:6
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. 相似文献
15.
The objective of this research is to investigate Fenton and persulfate oxidation with zero-valent iron [Fe(0)] as a batch type ex-situ remediation technology for the treatment of diesel-contaminated soil. Results from batch experiments indicate that Fe(0) is a better catalyst for H2O2 and persulfate than Fe2+ for the enhancement of Fenton and persulfate oxidation in a batch system. Maximum removal was obtained after 12 h when 1 and 2 g of Fe(0) were added to hydrogen peroxide (250 mg/L) and persulfate (250 mg/L), respectively, in a soil-water system. As the amounts of Fe(0) and persulfate were increased three times at the optimal ratio, the removal of total petroleum hydrocarbon (TPH) was enhanced accordingly. More than 90% of the TPH was removed in 3 h, and the treated soil met the Korean regulation level (500 mg/kg) for TPH. Increased amounts of Fe(0) and hydrogen peroxide (up to 10 g and 1250 mg/L, respectively) also significantly enhanced degradation under the optimal conditions. The results of our study suggest that Fe(0)-assisted Fenton and persulfate oxidation in a batch reactor may be an alternative option to treat diesel-contaminated soil. 相似文献
16.
The penetration of naphthaleneacetic acid (NAA) through enzymatically isolated pear leaf cuticle (Pyrus communis L. cv. Bartlett) is reported herein. Penetration of NAA increased with increasing lime and attained a steady state in approximately 20 minutes. The quantity of NAA penetrating was directly related to the concentration of the donor solution. NAA that penetrated the cuticle was shown to he unaltered. The Penetration of NAA from inside to outside is similar to that from outside to inside. Isolated stomatous lower cuticle permitted approximately 10-foId greater penetration of NAA than the astomatous upper cuticle. The penetration of NAA through isolated pear leaf cuticle is highly temperature dependent, exhibiting a temperature coefficient (Q10) of about 5.6 between 15° and 25 C. The low quantities of chemicals penetrating through the isolated cuticle reported herein and elsewhere are considered to he a characteristic of the technique and not an absolute limitation of the cuticle. Cuticular penetration could account for physiological quantities of NAA entering the plant. 相似文献
17.
The abilities of suspension cultures and intact roots of soybean (Glycine max L. cv. Hawkeye) to reduce ferric chelate were compared. Ferric chelate was supplied as ferric hydroxyethylethylenediaminetriacetic acid (FeHEDTA) and reduction was measured spectrophotometrically using bathophenan-throlinedisulfonic acid (BPDS) as the ferrous scavenger. Ferric chelate reduction by cell suspension cultures showed typical saturation kinetics; however, no difference was observed between cells that had been continuously grown with Fe (+Fe) and those that had been grown for four days without added Fe (–Fe). Values for Km and Vmax, determined from a Lineweaver-Burk plot, were 57 M and nmoles mg-1 dry weight for the +Fe cells and 50 M and 22 nmoles mg-1 dry weight for the -Fe cells, respectively. Ferric chelate reduction by Fe-deficient roots also exhibited saturation kinetics, while roots grown with adequate Fe did not reduce ferric chelate. The Km and Vmax values for Fe-deficient roots were 45 M and 20 nmoles mg-1 dry weight, respectively, and did not differ from values obtained for cells in culture. This study offers strong evidence that the mechanism responsible for the reduction of ferric chelate is the same for cultured cells and roots and that the process is controlled at the cellular level. We propose that suspension cultures can be used as an alternative to intact roots in the study of ferric chelate reduction. 相似文献
18.
Temporary soil flooding before cultivation alleviates iron chlorosis in crops grown on some calcareous Mexican Vertisols.
In order to investigate the effectiveness of such practice we carried out experiments with ten calcareous Vertisols from Mexico
and eight calcareous Inceptisols from Spain. In an incubation experiment, we studied the release of Fe2+ into the solution of soil suspensions in sealed vials with 5 m M CaCl2. In a pot experiment, we measured the leaf SPAD value (i.e. an estimate of leaf chlorophyll concentration) of lupin and strawberry
sequentially grown on a soil-sand mixture previously flooded for 30 days (SPADf value) and on a non-flooded (control) mixture (SPADc value). The amount of Fe2+ released by the soil at day 58 and the increase in oxalate-extractable Fe (Feo) upon incubation in vials were larger on average for the Inceptisols than for the Vertisols. The SPADc values for lupin and strawberry were (i) larger for the Vertisols than for the Inceptisols (probably because the Vertisols
contain little carbonate and induce less Fe chlorosis than the Inceptisols) and (ii) correlated with Feo, and with citrate/ascorbate- and DTPA-extractable Fe (Feca, FeDTPA). The SPADf-SPADc differencewas (i) much larger for the Inceptisols than for the Vertisols and (ii) correlated with the increases in Feo and Feca caused by flooding and with the amount of Fe2+ released in the incubation experiment. We hypothesize that the weak response of the Vertisols to flooding was partly a result
of their history including flooding episodes in the field, so a steady state had been reached in which the pool of Fe compounds
undergoing reductive dissolution and reprecipitating upon oxidation as poorly crystalline Fe oxides (the main source of phytoavailable
Fe) remained relatively constant and thus changed little after pot flooding. The Inceptisols, which had never been flooded
in the field, were capable of releasing Fe from sources other than poorly crystalline Fe oxides upon flooding, thus making
this treatment effective against Fe chlorosis. Our results point to the need to further study those soil chemical and mineralogical
properties that are related to increases in Fe phytoavailability upon temporary soil flooding. 相似文献
19.
The effect of soil moisture on the tolerance of Lupinus pilosus genotypes to a calcareous soil 总被引:1,自引:0,他引:1
Commercial narrow-leafed lupins (Lupinus angustifolius L.) grown on calcareous soils commonly display chlorotic symptoms resembling Fe deficiency. The severity of chlorosis increases with concurrent increases in soil moisture content. Our research has indicated that the rough-seeded lupin species, Lupinus pilosus Murr., has a range of adaptation to calcareous soils, from tolerant to intolerant. A pot experiment was conducted comparing a tolerant, a moderately tolerant and a moderately intolerant genotype of L. pilosus. Plants were grown for 35 days in a calcareous soil (50% CaCO3) at three moisture contents (80%, 100% and 120% of field capacity); the growth was compared with that on a fertile black cracking clay control soil at 70% of field capacity. Visual chlorosis score, chlorophyll meter readings, number of leaves and shoot dry weights were recorded at 14, 21, 28 and 35 days after sowing. Concentrations of chlorophyll, active Fe and nutrients in the youngest fully expanded leaves were also measured. Results showed that increased soil moisture increased the severity of chlorotic symptoms (increased chlorosis score) in all genotypes. The tolerant genotype showed significantly less symptoms than other genotypes at all moisture contents. All genotypes were able to recover from chlorosis symptoms at 80% moisture in the calcareous soil. Chlorosis score negatively correlated with chlorophyll meter readings, chlorophyll concentration and foliar active and total Fe, and Mn concentrations. Visual chlorosis score appeared to be a cost effective, accurate and efficient method enabling classification of the tolerance of genotypes. The chlorotic symptoms were likely to be due to HCO3
- induced nutrient deficiencies or a direct effect of HCO3
- on chlorophyll synthesis. This study indicates that the most probable mechanism of tolerance is related to an ability to prevent uptake of HCO3
- or efficiently sequester it once inside the root which prevents increases in internal pH and transport to the shoots. 相似文献
20.
Bench-scale experiments were performed to investigate the persistence of activated persulfate using citric acid (CA) chelated ferrous (Fe(II)), peroxide (H2O2), or hydroxide (OH?) activation in the presence of well-characterized aquifer solids. Chelation by citric acid was ineffective in controlling the interaction between persulfate and Fe(II), and oxidation of Fe(II) was observed, causing a rapid initial decrease in persulfate concentration. Subsequent to this loss, first-order persulfate degradation rate coefficients (kobs) were estimated, which were up to four times higher than the unactivated case due to the interaction with Fe(III), Fe(II), or CA. Total oxidation strength (TOS) was measured for peroxide activation experiments and was observed to decrease rapidly early due to peroxide degradation. This was followed by slow degradation kinetics similar to that of unactivated persulfate, implying that the initial TOS degradation was peroxide-dominated and the long-term kinetics were dominated by persulfate degradation. The kobs later used to capture TOS degradation were ~1 to 100 times higher than kobs for unactivated persulfate. For alkaline activation, kobs were only one to four times higher than unactivated persulfate, and therefore alkaline conditions demonstrated the least overall impact on persulfate stability among the various activation strategies explored. 相似文献