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1.
W. L. Lindsay 《Plant and Soil》1991,130(1-2):27-34
The solubility of Fe in soils is largely controlled by Fe oxides; ferrihydrite, amorphous ferric hydroxide, and soil-Fe are generally believed to exert the major control. Fe(III) hydrolysis species constitute the major Fe species in solution. Other inorganic Fe complexes are present, but their concentrations are much less than the hydrolysis species. Organic complexes of Fe including those of organic acids like citrate, oxalate, and malate contribute slightly to increased Fe solubility in acid soils, but not in alkaline soils.The most important influence that organic matter has on the solubilization of Fe is through reduction. Respiration of organic matter creates reduction microsites in soil where Fe2+ concentrations increase above those of the Fe(III) hydrolysis species. Fluctuating redox conditions in these microsites are conducive to the formation of a mixed valency ferrosic hydroxide. This metastable precipitate maintains an elevated level of soluble inorganic Fe for prolonged periods and increases Fe availability to plants. The release of reducing agents and acids next to roots, as well as the production of siderophores by microorganisms within the rhizosphere, contribute to the solubilization and increased availability of Fe to plants.  相似文献   

2.
Iron is vital for the establishment and function of symbiotic root nodules of legumes. Although abundant in the environment, Fe is often a limiting nutrient for plant growth due to its low solubility and availability in some soils. We have studied the mechanism of iron uptake in the root nodules of common bean to evaluate the role of nodules in physiological responses to iron deficiency. Based on experiments using full or partial submergence of nodulated roots in the nutrient solution, our results show that the nodules were affected only slightly under iron deficiency, especially when the nodules were submerged in nutrient solution in the tolerant cultivar. In addition, fully submerged root nodules showed enhanced acidification of the nutrient solution and showed higher ferric chelate reductase activity than that of partially submerged roots in plants cultivated under Fe deficiency. The main results obtained in this work suggest that in addition to preferential Fe allocation from the root system to the nodules, this symbiotic organ probably develops some mechanisms to respond to iron deficiency. These mechanisms were implied especially in nodule Fe absorption efficiency and in the ability of this organ to take up Fe directly from the medium.  相似文献   

3.
湿地植物根表的铁锰氧化物膜   总被引:44,自引:0,他引:44  
刘文菊  朱永官 《生态学报》2005,25(2):358-363
湿地植物根系具有泌氧能力 ,使其根表及根际微环境呈氧化状态。因而 ,土壤溶液中一些还原性物质被氧化 ,如 Fe2 ,Mn2 ,形成的氧化物呈红色或红棕色胶膜状包裹在根表 ,称为铁锰氧化物膜。铁锰氧化物膜及其根际微环境是湿地植物根系吸收养分和污染物的门户 ,势必会影响这些物质的吸收。主要综述了铁锰氧化物膜的形成和组成 ,以及根表形成的氧化物膜的生态效应 ,也就是氧化物胶膜对植物根系吸收外部介质中的养分及污染物质——重金属离子的影响  相似文献   

4.
Summary The combination of low Mn levels and high Fe levels in tissues of lowland rice varieties, as often encountered when rice is grown on acid soils, is not likely to result from an antagonistic effect of Fe on the uptake of Mn.Experiments with rice plants growing on sand, supplied with Fe and Mn, and subjected to various pH levels and moisture regimes, made it clear that under acid anaerobic conditions the absorption of Mn by rice plants is little affected by the presence of large quantities of Fe, and that under acid aerobic conditions the absorption of Fe by rice plants is little affected by the presence of large quantities of Mn.  相似文献   

5.
Fe nutrition demand and utilization by the green alga Dunaliella bardawil   总被引:2,自引:0,他引:2  
Keshtacher-Liebson  Ety  Hadar  Yitzhak  Chen  Yona 《Plant and Soil》1999,215(2):175-182
The Fe nutritional demands, requirements and mechanisms of uptake by Dunaliella bardawil as well as potential Fe sources were studied. A comparison between Fe uptake from bacterial siderophores and from synthetic ferric chelates revealed algal growth response and chlorophyll synthesis to increasing concentrations and availability at a range of 0.01 μM–5 μM, as well as differences in efficiency. Furthermore, chloroplast ultrastructure, as observed by TEM, was affected by Fe deficiency, as was chlorophyll content. Ferric reduction is involved in the Fe uptake mechanism of Fe-stressed D. bardawil. Nutrient solution with controlled levels of free Fe2+ as well as spectrophotometric assays were used to measure Fe3+ reduction. This study shows that D. bardawil utilizes Fe3+ via a reduction mechanism, similar to that of strategy-I higher plants. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

6.
Six differently distributed Poaceae species were compared in order to identify morphological and/or physiological properties that ensure calcicole species but not calcifuge species a sufficient Fe supply on CaCO3 rich soils. When grown at a range of FeEDTA supply from deficient to adequate, the calcicole species had higher Fe productivities and relative yields at low Fe supply than the calcifuges. Specific root surface and Fe uptake requirements were lower in calcicoles than in calcifuges. Root exudation of Fe-mobilizing compounds was monitored in plants grown either with or without added FeEDTA in hydroponic culture. Under Fe deficiency, typically more than 80% of soluble root exudates of Poaceae are phytosiderophores (Marschner et al., 1989; Römheld, 1987). Maximum exudation rates of Fe mobilizing compounds were 6.6 to 11.5 μmol g?1 root dry wt 2 hr?1 in calcicoles and 0.48 to 1.64 in calcifuges. If Fe requirement is defined as mean Fe uptake rate required for 90 % of the maximal relative growth rate, the exudation rates of Fe mobilizing compounds were at least 11.7 to 31.9 times higher than Fe requirements in calcicoles and 0.38 to 5.36 times higher in calcifuges. Growth response to a precipitated versus a chelated Fe source was determined. The relative ability to grow with Fe(OH)3 precipitate was correlated with the Fe mobilization rate of the species. The present results give evidence for the importance of Fe efficiency in wild plants. Calcicoles are able to live on calcareous soils partly because they produce larger amounts of Fe mobilizing compounds and have lower tissue Fe requirements than calcifuges.  相似文献   

7.
8.
Cadmium (Cd) has been identified as a significant pollutant due to its high solubility in water and soil and high toxicity to plants and animals. Rice, as one of the most important food crops, is grown in soils with variable levels of Cd and therefore, is important to discriminate the Cd tolerance of different rice cultivars to determine their suitability for cultivation in Cd-contaminated soils. This study investigates the primary mechanisms employed by four rice cultivars in attaining Cd tolerance. HA63 cultivar reduces Cd uptake by increasing Fe absorption through activation of phytosiderophores. T3028 cultivar accumulates the highest level of Cd in leaves while also activating its reactive oxygen species (ROS) scavenging system, including antioxidant enzymes and phytochelatins. In some rice cultivars (such as HA63), a cyanide-resistant respiration mechanism, important in Cd detoxification, was also promoted under the Cd stress. In conclusion, different rice cultivars may adopt different biochemical strategies and respond with different efficiency to Cd stress.  相似文献   

9.
J. J. Mortvedt 《Plant and Soil》1991,130(1-2):273-279
Correction of Fe chlorosis is done mainly by foliar sprays because soil applications generally are ineffective, especially for annual crops. Inorganic Fe sources applied to soils react rapidly to forms which are not as available to plants; ferrous Fe is oxidized to the ferric form in well-aerated soils, especially as soil pH increases. Several synthetic chelates and organic complexes have been used with varying success, depending upon Fe source and rate, application method, plant species, and weather and soil conditions. Use of Fe-efficient cultivars is one method of counteracting Fe deficiencies in some species. Future prospects for improving control of Fe chlorosis lie more with development of Fe-efficient cultivars of Fe-sensitive species than with development of improved Fe fertilizers and methods of application. The techniques of molecular biology should be applicable to help solve this important plant nutrition problem, but priority has not been given to conduct this research at this time.  相似文献   

10.
Regulatory mechanisms leading to cellular Fe homeostasis wereinvestigated inPlantago (Plantago lanceolata L.) plants grownhydroponically at different temperature regimes either in thepresence or absence of iron. During the experimental periodof 6 d, growth was not affected by Fe availability, but wasdecreased by lowering the root zone temperature (RZT) from 24to 12°C. Cultivating plants at low RZT decreased the reductionactivity for ferric chelates in Fe-deficient plants. In thepresence of iron, the temperature regime did not affect Fe accumulationby root cells, but decreased translocation of Fe to the shoot,and chlorosis of young leaves was observed at suboptimal RZT.Under these conditions root-mediated reduction of ferric chelateswas increased. In cold-treated plants this effect was specificto Fe and could not be evoked by Mn2+and Zn + 2additions. Supplementingthe medium with the ferrous scavenger ferrozine caused a furtherenhancement in reduction rates, probably due to mobilizationof apoplastic Fe. These results can be explained plausibly ifdifferent sites of Fe sensing are postulated and if it is assumedthat both the absence and presence of iron could be a signalincreasing root reduction activity. Copyright 2000 Annals ofBotany Company Adaptation, iron uptake regulation, ferric reduction, Plantago lanceolata, root zone temperature, whole plant signalling  相似文献   

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