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1.
A new technique of plant analysis to resolve iron chlorosis 总被引:4,自引:0,他引:4
Summary Iron though indispensable for the biosynthesis of chlorophyll, its total content in the plant was not associated with the occurrence of chlorosis. In order to overcome this inconsistency a new technique of plant iron analysis has been developed. It consists of the determination of Fe2+, the fraction of iron involved in the synthesis of chlorophyll.The choice of 1–10 o-phenanthroline (o-Ph) as an extractant for Fe2+ was based on its remarkably higher stability constant for Fe2+ than Fe3+. On this basis, it could preferentially chelate Fe2+. The highly specific organce colour of the Fe2+-phenanthroline complex made possible the determination of Fe2+ by reading the transmittancy at 510 nm.The procedure involves extraction of 2 g of thoroughly washed, chopped, fresh plant by 20 ml of o-phenanthroline extractant (pH 3.0, conc. 1.5%). The plant samples treated with the extractant are allowed to stand for 16 hours and Fe2+ is determined in the filtrate by reading the transmittancy at 510 nm.In sharp contrast to total iron the green plants always contained more Fe2+ than chlorotic plants. The technique has been developed for rice but is expected to be successful for other crops also. 相似文献
2.
Ten mungbean cultivars were evaluated for their resistance to iron deficiency in view of chlorosis symptoms, plant growth and seed yield under field conditions on a calcareous soil in Thailand. The KPS2 cultivar was highly susceptible; the KPS1, PSU1 and Pag-asa 1 cultivars were somewhat susceptible; the VC1163B cultivar was moderately tolerant; the CN36, CN60, UT1 and CNM-I cultivars were tolerant; and the CNM8509B cultivar was very tolerant to iron deficiency. Foliar application of a solution of 5 g L-1 ferrous sulphate was effective in correcting chlorosis that was induced by iron deficiency, and it enhanced both the growth and the yield of susceptible cultivars. Compared with the susceptible cultivar KPS2, the tolerant cultivar UT1 had a greater ability to lower the pH of the nutrient solution in response to iron deficiency. The root-associated Fe3+-reduction activity of UT1 that had been grown in -Fe medium was similar to that of the plants grown in +Fe medium when the acidification of the medium occurred. Acidification of the medium in response to iron deficiency might contribute to the efficient solubilization of iron from calcareous soils, and it related more closely to the resistance to iron deficiency than Fe3+ reduction by roots in mungbean cultivars. 相似文献
3.
Differences in responses to iron deficiency between two chickpea cultivars, NP-62 and K-850, were examined. The apical leaves of NP-62 quickly showed symptoms of iron-deficiency chlorosis when grown on an iron-free medium. By contrast, K-850 showed no visible symptoms on the same medium. Iron contents of the apical leaves of these two cultivars were similar during the first 7 days after they were transferred to the iron-free medium in spite of a marked difference in root-associated Fe3+-reduction activity. The susceptibility to iron-deficiency chlorosis observed in NP-62 was not attributable to the poor Fe3+-reduction activity of roots but to the inefficient utilization of iron within leaves under conditions when the supply of iron was limited. 相似文献
4.
pH Changes Associated with Iron-Stress Response 总被引:3,自引:0,他引:3
When Fe-inefficient T3238fer and Fe-efficient T3238FER tomatoes were supplied iron, and nitrogen as nitrate, they increased the pH of the nutrient culture. When they were supplied nitrogen as ammonium, they decreased the pH. When Fe supply was limited, Fe-stress response developed in T3238FER that opposed the usual nitrate response and decreased, rather than increased, the pH. A “reductant” which reduced Fe3+ to Fe2+ was released from the roots of these plants and lowered the pH; and there was a tremendous increase in the uptake of Fe. T3238fer did not produce “reductant” in response to Fe-stress; the pH increased, and the plants developed Fe-deficiency when nitrogen was supplied as nitrate. Nitrogen nutrition and iron-stress response are important factors associated with iron chlorosis in plants. Release of hydrogen ions from roots of Fe-stressed plants is caused by more than response to imbalanced uptake of cations and anions. 相似文献
5.
David O. Lambeth Gwen R. Ericson Mark A. Yorek Paul D. Ray 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,719(3):501-508
The influences of buffers and iron chelators on the rate of autoxidation of Fe2+ were examined in the pH range 6.0–7.4. The catalysis by Fe2+ and Fe3+ of the autoxidation of dithiothreitol was also investigated. In buffers which are non- or poor chelators of iron, 0.25 mM Fe2+, and 0.3 mM dithiothreitol when present with iron, oxidize within minutes at pH 7.4 and 30°C. The stability of each increases as the pH is decreased and more than 90% of each remains after 1 h at pH 6.0. In the presence of buffers or oxy-ligands which preferentially and strongly chelate Fe3+ over Fe2+, Fe2+ autoxidizes rapidly in the pH range 6.0–7.4 while dithiothreitol is protected. Ligands which preferentially bind strongly to Fe2+ stabilize both Fe2+ and dithiothreitol at pH 7.4. Dithiothreitol readily reduces Fe3+ in non-chelating buffers or in the presence of strong chelators of Fe2+, however, the ferrous ions produced are prone to reoxidation at higher pH values. These results show that Fe2+ and dithiothreitol are very susceptible to autoxidation in the neutral pH range, and that the rates are strongly influenced by the presence of chelators of Fe2+ and Fe3+. The rapid autoxidations of these species need to be taken into account when designing and interpreting experiments involving Fe2+ or both dithiothreitol and iron. 相似文献
6.
Two light sources differentially affected ferric iron reduction and growth of cotton 总被引:1,自引:0,他引:1
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In growth chambers, low pressure sodium (LPS) plus incandescent (Inc) lamps and fluorescent cool-white (FCW) plus Inc lamps were used to determine their effects on growth of cotton (Gossypium hirsutum L.) and on the reduction of Fe3+ to Fe2+. Cotton plants grown under LPS + Inc light developed chlorosis and grew poorly, whereas plants grown under FCW + Inc lights were green. The chlorophyll concentration and top and root weights of cotton grown under LPS + Inc were lower than those under FCW + Inc. In solution, FCW + Inc lamps reduced about eight times more Fe3+ to Fe2+ than did LPS + Inc lamps. Fe3+ is transported to plant tops as Fe3+ citrate and if we assume that FCW + Inc light reduces Fe3+ to Fe2+ in plant foliage as it did in the solutions, then reduction of Fe3+ by the light environment will make Fe2+ in the tops more available for biochemical reactions. 相似文献
7.
Pauline Y. Ladiges 《Plant and Soil》1977,48(3):581-597
Summary In comparing two populations of E. viminalis observations indicated that plants of a calcareous population (i) showed a greater yield at high pH, and when subjected to Fe-stress, (ii) took longer to develop chlorosis, (iii) more quickly developed new roots, and (iv) were capable of removing more Fe from solution than were plants of an acid population. Some Fe-stressed plants also appeared to be able to reduce Fe3+ to Fe2+, but population differences have not yet been clearly established. Plants from an acidic population accumulated very high levels of P in leaves when grown in alkaline solutions and, consequently, exhibited high P/Fe ratios, chlorosis, and symptoms of P toxicity. 相似文献
8.
Elisabeth M. Froschauer Rudolf J. Schweyen Gerlinde Wiesenberger 《生物化学与生物物理学报:生物膜》2009,1788(5):1044-1050
The yeast proteins Mrs3p and Mrs4p are two closely related members of the mitochondrial carrier family (MCF), which had previously been implicated in mitochondrial Fe2+ homeostasis. A vertebrate Mrs3/4 homologue named mitoferrin was shown to be essential for erythroid iron utilization and proposed to function as an essential mitochondrial iron importer. Indirect reporter assays in isolated yeast mitochondria indicated that the Mrs3/4 proteins are involved in mitochondrial Fe2+ utilization or transport under iron-limiting conditions. To have a more direct test for Mrs3/4p mediated iron uptake into mitochondria we studied iron (II) transport across yeast inner mitochondrial membrane vesicles (SMPs) using the iron-sensitive fluorophore PhenGreen SK (PGSK). Wild-type SMPs showed rapid uptake of Fe2+ which was driven by the external Fe2+ concentration and stimulated by acidic pH. SMPs from the double deletion strain mrs3/4Δ failed to show this rapid Fe2+ uptake, while SMPs from cells overproducing Mrs3/4p exhibited increased Fe2+ uptake rates. Cu2+ was transported at similar rates as Fe2+, while other divalent cations, such as Zn2+ and Cd2+ apparently did not serve as substrates for the Mrs3/4p transporters. We conclude that the carrier proteins Mrs3p and Mrs4p transport Fe2+ across the inner mitochondrial membrane. Their activity is dependent on the pH gradient and it is stimulated by iron shortage. 相似文献
9.
Freshly-added iron only slightly affected the growth of iron-sufficient cells of the green alga Scenedesmus incrassatulus Bohl, strain R-83, but induced accumulation of malondialdehyde (MDA) in cells and excretion of MDA in the medium. These effects were stronger in response to Fe2+ as compared to Fe3+, but Fe3+ induced the release of more iron-binding chelators from these cells than Fe2+. Fe3+ added either in dark or in light induced release of equal concentrations of iron-complexing agents, part of which formed strong chelates with iron in the medium. Exogenously added hydrogen peroxide inhibited iron-induced release of chelators but the effect was removed by addition of the hydroxyl radical scavenger dimethylsulfoxide (DMSO). Malondialdehyde also inhibited the release of chelators. Release of chelators was induced in the absence of iron salts by photoexcited chlorophyll (Chl). The Chl-induced release was efficiently inhibited by singlet oxygen scavengers such as dimethylfuran, -carotene, sodium azide and vitamin B6, and stimulated in D2O or DMSO. Exogenously added catalase inhibited the release more than added superoxide dismutase. The Fe3-induced release of chelators was also inhibited by scavengers of singlet oxygen, but was not affected by sodium azide and by ethanol. Hence both H2O2 and singlet oxygen were involved in induction of chelator release in the absence of iron in light. The induction of chelator release by iron in dark involved H2O2, but not singlet oxygen. 相似文献
10.
11.
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
12.
Quince (Cydonia oblonga Mill.), pear (Pyrus communis L.) and olive (Olea europaea L.) genotypes were evaluated for their tolerance to iron deficiency stress by growing young plants in three types of aerated nutrient solutions: (1) with iron, (2) without iron or (3) low in iron and with 10 mM bicarbonate. Plants were obtained either from rooted softwood cuttings or from germination of seeds. The degree of tolerance was evaluated with several indices: (1) the chlorophyll content, (2) the root Fe3+ reducing capacity and (3) the whole plant relative growth. Fifteen hours before Fe3+ reducing capacity determination, iron was applied to the roots of plants with iron-stress, since this method resulted in increasing the reductase activity. All quince and pear genotypes increased the root Fe3+ reducing capacity when grown in the treatments for iron-stress, in relation to control plants of the same genotypes. In olive cultivars, the Fe3+ reducing capacity was lower in the iron-stress treatments than in the control one. Studying the relationship between relative growth and chlorophyll content for each genotype under iron-stress, in relation to both indices in control plants, a classification of species and genotypes was established. According to that, most olive cultivars and some pear rootstocks and cultivars appear more iron-efficient than quince rootstocks. Our study shows that in some woody species, determining root Fe3+ reducing capacity is not the best method to establish tolerance to iron deficiency stress. 相似文献
13.
Iron-efficient (WF9 corn and Coker 227 oat) and Fe-inefficient (ys1 corn and TAM 0–312 oat) cultivars were comparatively tested for their response to Fe-deficiency stress induced by the use of either ferrous or ferric chelators. Corn and oats were grown in 20 M Fe with 0, 60, and 120 M BPDS and 40 M Fe with 0, 120, and 240 M BPDS and 20 M Fe with 0 and 40 M EDDHA. All four cultivars tested, both Fe-efficient and Fe-inefficient, continuously reduced Fe3+ to Fe2+ at a low level as evidenced by the production of Fe2+ (BPDS)3 in test nutrient solutions over time. Severity of chlorosis increased as more BPDS was added to the nutrient solutions for both WF9 and ys1 corn, but unlike corn, Coker 227 and TAM 0-312 oats were both able to obtain Fe from the Fe2+ (BPDS)3 complex and were less chlorotic as a result. In short-term (4-hour) in vivo measurements, iron-stressed WF9 (Fe-efficient) corn reduced more Fe3+ to Fe2+ than similarly stressed ys1 corn, Coker 227 oat or TAM 0-312 oat. Thus, at the same time that Fe-efficient WF9 corn reduces more Fe than the other cultivars, it is also unable to compete with BPDS for that Fe in the nutrient solution. These differences coupled with the observation that only Coker 227 oat produced measureable iron solubilizing substances (phytosiderophores) suggest that these two species differ in their mechanisms for obtaining Fe during Fe-deficiency stress. 相似文献
14.
María Eugenia Letelier Sebastián Sánchez-Jofré Liliana Peredo-Silva Juan Cortés-Troncoso Paula Aracena-Parks 《Chemico-biological interactions》2010,188(1):220-227
Iron and copper ions, in their unbound form, may lead to the generation of reactive oxygen species via Haber–Weiss and/or Fenton reactions. In addition, it has been shown that copper ions can irreversibly and non-specifically bind to thiol groups in proteins. This non-specific binding property has not been fully addressed for iron ions. Thus, the present study compares both the pro-oxidant and the non-specific binding properties of Fe3+ and Cu2+, using rat liver cytosol and microsomes as biological systems. Our data show that, in the absence of proteins, Cu2+/ascorbate elicited more oxygen consumption than Fe3+/ascorbate under identical conditions. Presence of cytosolic and microsomal protein, however, differentially altered oxygen consumption patterns. In addition, Cu2+/ascorbate increased microsomal lipid peroxidation and decreased cytosolic and microsomal content of thiol groups more efficiently than Fe3+/ascorbate. Finally, Fe3+/ascorbate and Cu2+/ascorbate inhibited in different ways cytosolic and microsomal glutathione S-transferase (GST) activities, which are differentially sensitive to oxidants. Moreover, in the absence of ascorbate, only Cu2+ decreased the content of cytosolic and microsomal thiol groups and inhibited cytosolic and microsomal GST activities. Catechin partially prevented the damage to thiol groups elicited by Fe3+/ascorbate and Cu2+/ascorbate but not by Cu2+ alone. N-Acetylcysteine completely prevented the damage elicited by Cu2+/ascorbate, Fe3+/ascorbate and Cu2+ alone. N-Acetylcysteine also completely reversed the damage to thiol groups elicited by Fe3+/ascorbate, partially reversed that of Cu2+/ascorbate but failed to reverse the damage promoted by Cu2+ alone. Our data are discussed in terms to the potential damage that the accumulation of iron and copper ions can promote in biological systems. 相似文献
15.
Konrad Mengel 《Plant and Soil》1994,165(2):275-283
The article describes factors and processes which lead to Fe chlorosis (lime chlorosis) in plants grown on calcareous soils. Such soils may contain high HCO3
- concentrations in their soil solution, they are characterized by a high pH, and they rather tend to accumulate nitrate than ammonium because due to the high pH level ammonium nitrogen is rapidly nitrified and/or even may escape in form of volatile NH3. Hence in these soils plant roots may be exposed to high nitrate and high bicarbonate concentrations. Both anion species are involved in the induction of Fe chlorosis.Physiological processes involved in Fe chlorosis occur in the roots and in the leaves. Even on calcareous soils and even in plants with chlorosis the Fe concentration in the roots is several times higher than the Fe concentration in the leaves. This shows that the Fe availability in the soil is not the critical process leading to chlorosis but rather the Fe uptake from the root apoplast into the cytosol of root cells. This situation applies to dicots as well as to monocots. Iron transport across the plasmamembrane is initiated by FeIII reduction brought about by a plasmalemma located FeIII reductase. Its activity is pH dependent and at alkaline pH supposed to be much depressed. Bicarbonate present in the root apoplast will neutralize the protons pumped out of the cytosol and together with nitrate which is taken up by a H+/nitrate cotransport high pH levels are provided which hamper or even block the FeIII reduction.Frequently chlorotic leaves have higher Fe concentrations than green ones which phenomenon shows that chlorosis on calcareous soils is not only related to Fe uptake by roots and Fe translocation from the roots to the upper plant parts but also dependent on the efficiency of Fe in the leaves. It is hypothesized that also in the leaves FeIII reduction and Fe uptake from the apoplast into the cytosol is affected by nitrate and bicarbonate in an analogous way as this is the case in the roots. This assumption was confirmed by the highly significant negative correlation between the leaf apoplast pH and the degree of iron chlorosis measured as leaf chlorophyll concentration. Depressing leaf apoplast pH by simply spraying chlorotic leaves with an acid led to a regreening of the leaves. 相似文献
16.
Summary The release of iron from ferritin is important in the formation of iron proteins and for the management of diseases in both animals and plants associated with abnormal accumulations of ferritin iron. Much more iron can be released experimentally by reduction of the ferric hydrous oxide core than by chelation of Fe3+ which has led to the notion that reduction is also the major aspect of iron release in vivo. Variations in the kinetics of reduction of the mineral core of ferritin have been attributed to the redox potential of the reductant, redox properties of the iron core, the structure of the protein coat, the analytical method used to detect Fe2+ and reactions at the surface of the mineral. Direct measurements of the oxidation state of the iron during reduction has never been used to analyze the kinetics of reduction, although Mössbauer spectroscopy has been used to confirm the extent of reduction after electrochemical reduction using dispersive X-ray absorption spectroscopy (DXAS). We show that the near edge of X-ray absorption spectra (XANES) can be used to quantify the relative amounts of Fe2+ and Fe3+ in mixtures of the hydrated ions. Since the nearest neighbors of iron in the ferritin iron core do not change during reduction, XANES can be used to monitor directly the reduction of the ferritin iron core. Previous studies of iron core reduction which measured by Fe2+ · bipyridyl formation, or coulometric reduction with different mediators, suggested that rates depended mainly on the redox potential of the electron donor. When DXAS was used to measure the rate of reduction directly, the initial rate was faster than previously measured. Thus, previously measured differences in reduction rates appear to be influenced by the accessibility of Fe2+ to the complexing reagent or by the electrochemical mediator. In the later stages of ferritin iron core dissolution, reduction rates drop dramatically whether measured by DXAS or formation of Fe2+ complexes. Such results emphasize the heterogeneity of ferritin core structure. 相似文献
17.
Iron chlorosis is commonly corrected by the application of EDDHA chelates, whose industrial synthesis produces o,oEDDHA together with a mixture of regioisomers and other unknown by-products. HJB, an o,oEDDHA analogous, is a new chelating agent with a purer synthesis pathway than EDDHA. The HJB/Fe3+ stability constant is intermediate between the racemic and meso o,oEDDHA/Fe3+ stereoisomers. This work studied the efficacy of HJB as a Fe source in plant nutrition. No significant differences between o,oEDDHA/Fe3+, HJB/Fe3+ and HBED/Fe3+ were observed when they are used as substrates of the iron-chelate reductase of mild chlorotic cucumber plants. Chelates prepared with the stable isotope 57Fe were used in both soil and hydroponic experiments. In the hydroponic experiment, nutrient solutions with low doses of chelates were renewed weekly. Soybean plants treated with o,oEDDHA/57Fe3+ recorded the highest results in biomass, SPAD index and Fe nutrition. In the soil experiment, chelates were added once at a rate of 2.5 mg Fe per kg of a calcareous soil. Soybean plants treated with HJB/57Fe3+ recorded a higher biomass and SPAD index in young leaves than the plants treated with o,oEDDHA/57Fe3+; however, 57Fe and total Fe concentrations in leaves were lower. The results of both pot experiments are associated with a faster ability by o,oEDDHA to provide Fe to the plants and with a more continuous supply of Fe from HJB/Fe3+. HJB/57Fe3+ effectively alleviated the Fe-deficiency chlorosis of soybean with a longer lasting effect than o,oEDDHA/57Fe3+. 相似文献
18.
Mechanisms causing the calcifuge–calcicole behavior of lichens are largely unexplored. Studying the case examples of two closely related terricolous lichens, the calcifuge Cladonia furcata subsp. furcata and the calcicole C. rangiformis, we found that preference for acidic or calcareous soils in these lichens is related to iron and phosphate uptake as in vascular plants. In laboratory studies, the calcicole species was more efficient in the intracellular uptake of Fe3+ and phosphate at pH 8 than the calcifuge species. At pH 3, intracellular uptake of Fe2+ in the calcicole species significantly exceeded that in the calcifuge species suggesting that calcicole lichens suffer from toxicity symptoms by excess Fe2+ at acidic sites. Though these observations parallel findings from calcifuge and calcicole vascular plants, mechanisms leading to the different iron and phosphate uptake characteristics in the studied calcifuge and calcicole lichens may differ from those in vascular plants and should be the topic of future research. A role of the depside atranorin in facilitating iron uptake by reducing Fe3+ in the apoplast is hypothesized. 相似文献
19.
C. Derrick QuarlesJr. R. Kenneth Marcus Julia L. Brumaghim 《Journal of biological inorganic chemistry》2011,16(6):913-921
Competitive binding of Fe3+, Cr3+, and Ni2+ to transferrin (Tf) was investigated at various physiological iron to Tf concentration ratios. Loading percentages for these
metal ions are based on a two M
n+ to one Tf (i.e., 100% loading) stoichiometry and were determined using a particle beam/hollow cathode–optical emission spectroscopy
(PB/HC-OES) method. Serum iron concentrations typically found in normal, iron-deficient, iron-deficient from chronic disease,
iron-deficient from inflammation, and iron-overload conditions were used to determine the effects of iron concentration on
iron loading into Tf. The PB/HC-OES method allows the monitoring of metal ions in competition with Fe3+ for Tf binding. Iron-overload concentrations impeded the ability of chromium (15.0 μM) or nickel (10.3 μM) to load completely
into Tf. Low Fe3+ uptake by Tf under iron-deficient or chronic disease iron concentrations limited Ni2+ loading into Tf. Competitive binding kinetic studies were performed with Fe3+, Cr3+, and Ni2+ to determine percentages of metal ion uptake into Tf as a function of time. The initial rates of Fe3+ loading increased in the presence of nickel or chromium, with maximal Fe3+ loading into Tf in all cases reaching approximately 24%. Addition of Cr3+ to 50% preloaded Fe3+–Tf showed that excess chromium (15.0 μM) displaced roughly 13% of Fe3+ from Tf, resulting in 7.6 ± 1.3% Cr3+ loading of Tf. The PB/HC-OES method provides the ability to monitor multiple metal ions competing for Tf binding and will
help to understand metal competition for Tf binding. 相似文献
20.
While lupins suffer severely from Fe deficiency when grown on calcareous soils, field peas under the same conditions grow
normally. This paper aimed to identify whether these differences were related to differences in either the pattern or capacity
for rhizosphere acidification or Fe3+ reduction between these species.
Two lupin species (Lupinus angustifolius, L. cosentinii) and field peas (Pisum sativum) were grown in solution culture for 5 weeks with both an adequate and a low supply of Fe. Plants were reliant on symbiotically
fixed N. The extent of iron reduction was determined using the chelates TPTZ and BPDS. The pattern of reactions around roots
was determined by placing roots in agar containing either bromocresol purple or TPTZ.
The low supply of Fe decreased the growth of lupins by over 30% and induced severe chlorosis and necrosis. Growth of the peas
was reduced by less than 15% and no symptoms appeared. All species acidified the solutions by about 1 pH unit regardless of
the Fe treatment. The level of Fe3+ reduction was higher for all species grown with low Fe than with adequate Fe. Capacity for Fe3+ reduction was higher for all species grown with low Fe than with adequate Fe. Capacity for Fe3+ reduction was similar for all species. The pattern of acidification and reduction around roots was also similar between species.
Thus it appears that the capacity of lupins to reduce Fe3+ in the rhizosphere is not the primary cause of Fe deficiency in lupins. 相似文献