玉米、小麦与花生间作改善花生铁营养机制的探讨

采用土培盆栽方法模拟研究了玉米／花生、小麦／花生间作对花生铁营养状况的影响及其作用机制。结果表明,禾本科作物与花生间作对花生的铁营养状况有显著影响：当花生与玉米或小麦分别间作时,花生新叶叶色正常,而花生单作则表现出严重的缺铁黄化现象,间作花生新叶活性铁、叶绿素含量明显高于单作,两种间作花生各部位铁含量和吸收量明显高于单作,间作明显地促进了铁向花生地上部的转移;在单作花生表现缺铁症状１４ｄ的时间范围内,其根系质外体铁含量仅是间作花生的５２％～８０％;而根系还原力则是单作花生在表现缺铁症状后迅速提高,至缺铁第６ｄ时还原力达到最大值,随后花生根系还原力迅速下降,而间作花生在０～１４ｄ内还原力增加速度缓慢,在１０～１４ｄ中其根系还原力明显地高于单作花生根系还原力。其主要原因可能是禾本科作物玉米、小麦根系分泌物（如：麦根酸类植物铁载体）螯合土壤中难溶性铁并被花生吸收利用。     

不同禾本科作物与花生混作对花生根系质外体铁的累积和还原力的影响

采用土培盆栽方法模拟玉米／花生、大麦／花生、燕麦／花生、小麦／花生、高粱／花生5种种植方式,研究混作对花生根系质外体铁的累积和还原力的影响．结果表明,当花生与5种分泌植物铁载体能力不同的禾本科作物混作时,花生新叶叶色正常,而单作花生则表现出严重的缺铁黄化症状,混作花生各部位的含铁量明显增加．与麦类作物(大麦、燕麦、小麦)混作的花生其各部位铁含量高于与玉米、高粱混作的花生,说明麦类作物改善花生铁营养的能力强于玉米、高粱,而两个玉米品种之间的能力差异不大。这主要是由于麦类作物分泌植物铁载体能力高于玉米、高粱．在花生生长至第50、60和70d时,混作花生根系质外体铁含量也随着逐渐增加,并始终高于单作花生．同时,混作明显地提高了花生根际土壤有效铁的含量,花生根系还原力也逐步提高．混作花生逐渐提高的还原力和介质中不断供给的易被花生还原吸收的铁。在改善花生的铁营养方面起了重要的作用．     

大豆根系质外体铁库的累积及其在缺铁时被利用的规律

采用营养液培养法研究了在不同程度的缺铁条件下,大豆（Ｇｌｙｃｉｎｅｍａｘ（Ｌ．）Ｍｅｒｒ．）根系质外体铁库累积与利用的规律,及其在缓解植物缺铁胁迫方面的作用。结果表明,缺铁处理下,大豆根系质外体铁库不断被再利用直至枯竭,根系还原力与过氧经物酶活性呈升降有序的周期性变化,从而一定程度上缓解缺铁胁迫,延缓植株缺铁症状的出现,新叶叶绿素和活性铁含量缓慢下降,而低铁条件下（供应１０＾－６ｍｏｌ／ＬＦｅＥＣ     

不同禾本科作物与花生混作对花生根系质外体铁的累积和还原力的影响

采用土培盆栽方法模拟玉米/花生、大麦/花生、燕麦/花生、小麦/花生、高粱/花生5种种植方式,研究混作对花生根系质外体铁的累积和还原力的影响.结果表明,当花生与5种分泌植物铁载体能力不同的禾本科作物混作时,花生新叶叶色正常,而单作花生则表现出严重的缺铁黄化症状,混作花生各部位的含铁量明显增加.与麦类作物(大麦、燕麦、小麦)混作的花生其各部位铁含量高于与玉米、高粱混作的花生,说明麦类作物改善花生铁营养的能力强于玉米、高粱,而两个玉米品种之间的能力差异不大,这主要是由于麦类作物分泌植物铁载体能力高于玉米、高粱.在花生生长至第50、60和70d时,混作花生根系质外体铁含量也随着逐渐增加,并始终高于单作花生.同时,混作明显地提高了花生根际土壤有效铁的含量,花生根系还原力也逐步提高.混作花生逐渐提高的还原力和介质中不断供给的易被花生还原吸收的铁,在改善花生的铁营养方面起了重要的作用.     

潜在性缺铁条件下大豆根系质外体铁库的积累与利用

用营养液培养方法研究了在不同供铁条件下,大豆根系质外体铁库的积累与活化利用。结果表明：1、供应难溶性Fe（OH）3,大豆根系质外体铁库呈现出积累与亏缺的节律性变化。与之相应出现根系还原力的降低与升高的节律性变化,但地上部总铁含量和新叶叶绿素含量均无变化。说明了根系质外体铁库的利用,维持了大豆正常生长需铁。2、对缺铁植株脉冲供铁后,大豆根系质外体铁库首先出现明显积累,随后一直处于下降状态,与此同时根系还原力表现出相应的变化,前期下降,后期有波动。地上部总铁含量与新叶叶绿素含量的变化与前两者密切联系,出现升高、降低不同趋势的变化。     

玉米,小麦与花间作改善花生铁营养机制的探讨

采用土培盆栽方法模拟研究了玉米／花生、小麦／花生间作对花生铁营养状况的影响及其作用机制。结果表明,禾本科作物与花生间作对花生的铁营养显著影响;当花生与玉米或小麦分别间作时,花生新叶叶色正常,而花生单作则表现出严重的缺铁花化现象,间作花生新叶活性铁、叶绿素含量明显高单作,途中瞳作花生各部位铁含量和吸收量明显高于单作,间作灶促进了铁向花生地上部的转移;在单作花生表现缺铁症状１４ｄ的时间范围内,其根系质     

O3浓度升高对小麦根际土壤酶活性和有机酸含量的影响

近地层臭氧(O₃)浓度升高作为全球气候变化的重要因素之一,对土壤生态环境和农作物生长发育造成了很大影响.本研究采用开顶式气室(OTCs)法,探究臭氧浓度升高对小麦不同生育期(分蘖期、拔节期、孕穗期和成熟期)根际土壤酶活性(过氧化氢酶、多酚氧化酶、脱氢酶和转化酶)和有机酸含量(草酸、柠檬酸和苹果酸)的影响规律,并结合根际土壤理化性质、植株根系生长状况等分析其产生影响的原因.结果表明: O₃浓度升高不同程度地提高了小麦成熟期土壤过氧化氢酶、多酚氧化酶、脱氢酶和转化酶活性,其中过氧化氢酶和多酚氧化酶活性提高达显著水平;在抽穗期,脱氢酶和转化酶活性因臭氧浓度升高而显著提高,增幅最高可达76.7%.在成熟期,O₃浓度升高显著提高了根际土壤中柠檬酸和苹果酸含量;显著降低了根际土壤pH、电导率、总碳和总氮含量,增加了土壤氧化还原电位(Eh);显著降低了小麦根系生物量、总根长和根总表面积,而增加了根平均直径.     

三种根系分泌脂肪酸对花生生长和土壤酶活性的影响

为了探讨花生连作后土壤中脂肪酸类物质的累积与花生连作障碍间的关系,为花生连作障碍机理的研究提供新的理论依据,以田间土壤为介质,采用盆栽试验的方法研究了花生根系分泌物中3种长链脂肪酸,即:豆蔻酸、软脂酸和硬脂酸的混合物,对花生植株生长、产量和土壤酶活性的影响。结果表明,当土壤中脂肪酸的初始含量较低时(80 mg/kg土),对花生植株的生长和产量有微弱的促进作用(P>0.05),当土壤中脂肪酸的初始含量较高时(160 mg/kg土和240 mg/kg土),显著抑制了花生植株的生长和产量(P<0.05)。叶片叶绿素含量、根系活力、土壤酶(蔗糖酶、脲酶、磷酸酶)活性在低脂肪酸含量处理下升高,在高脂肪酸含量处理下显著降低(P<0.001)。光合产物、根际有效养分的减少和根系养分吸收能力的降低,可能是导致花生植株生长和产量降低的原因之一。花生连作土壤中豆蔻酸、软脂酸和硬脂酸的累积与花生的连作障碍有着密切关系。     

缺铁敏感度不同的大豆品种对缺铁的适应机制

与供铁处理相比,对缺铁敏感的大豆品种“哈８３”幼苗在缺铁胁迫条件下根际没有酸化现象,根系对Ｆｅ（Ⅲ）的还原能力也没有明显增强。但抗缺铁的大豆品种“８７０１”幼苗根际则严重酸化,根系对Ｆｅ（Ⅲ）的还原能力显著增强;加入能抑制根系Ｈ＋－ＡＴＰ酶活性、减弱根际酸化作用的Ｈ＋－ＡＴＰ酶抑制剂正钒酸钠会降低根系对Ｆｅ（Ⅲ）的还原能力;说明根际酸化与根系还原Ｆｅ（Ⅲ）能力相互联系,初步证实根细胞原生质膜Ｈ＋－ＡＴＰ酶和缺铁诱导的还原酶相互偶联的假说。     

缺铁敏感度不同的大豆品种对缺铁的适应机制

与供铁处理相比,对缺铁敏感的大豆品种“哈８３”幼苗在缺铁胁迫和上根际没有酸化现象,根系对Ｆｅ（Ⅲ）的还原能力也没有明显增强。但抗缺铁的大豆品种“８７０１”幼苗根际则严重酸化,根系对Ｆｅ（Ⅲ）的还原能力显著增强;加入能抑制根系Ｈ＾＋－ＡＴＰ酶活性、减弱根际酸化作用的Ｈ＾＋－ＡＴＰ酶抑制剂正钒酸钠会降低根系对Ｆｅ（Ⅲ）的还原能力;说明根际酸化与根系还原Ｆｅ（Ⅲ）能力相互联系,初步证实根细胞原生质膜Ｈ＾     

Genotypical differences in responses to iron deficiency between sensitive and resistant cultivars of chickpea (Cicer arietinum)

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.     

Bicarbonate concentration as affected by soil water content controls iron nutrition of peanut plants in a calcareous soil.

Strategy I peanut plants are frequently subjected to iron deficiency when growing in calcareous soils, which contain high concentrations of bicarbonate. In calcareous soils under field conditions, it has been noted that chlorosis increases in severity after excessive rainfall or irrigation, but the chlorosis symptoms of peanuts are alleviated after waterlogged soils dry. A pot experiment was conducted simulating the chlorosis symptom observed in the field when peanut plants are exposed to fluctuating soil water content induced from rainfall or irrigation. We investigated the bicarbonate fluctuations resulting from adjustable soil water content (SWC) that could lead to bicarbonate-induced iron chlorosis of peanuts growing in calcareous soil. The experiments included three treatments of SWC (50% of water holding capacity (WHC), 80% of WHC, and 100% of WHC) under two levels of CaCO(3) concentrations (at 8.67% and 18.67%.) The results showed that the iron nutrition of peanuts could be regulated by different SWC at both CaCO(3) levels. Our observations indicate that iron deficiency chlorosis symptoms in peanuts grown in high soil water content were more severe, compared to those of peanuts in lower soil water content. A shift from high soil water content to lower soil water content could improve or eliminate the iron deficiency chlorosis symptom of peanuts. The HCO(3)(-) concentration in the peanut rhizosphere increased with increasing SWC and CaCO(3) content and it correlated with the level of soil water content. We suggest that variations in the soil water content could induce HCO(3)(-) concentration variation in the rhizosphere of peanuts. Consequently, the high HCO(3)(-) concentration, which is induced by a high water content in calcareous soil and a high CaCO(3) level, could inhibit the physiological response to iron deficiency of peanuts, resulting in iron deficiency chlorosis. The study indicates that a reasonable agricultural practice of irrigation and drainage should be considered to improve and prevent iron deficiency chlorosis of strategy I plants in calcareous soil.     

Iron deficiency in chickpea in the Mediterranean region and its control through resistant genotypes and nutrient application

Iron-deficiency chlorosis is commonly observed in some genotypes of chickpea (Cicer arietinum L.) in the Mediterranean region of West Asia and North Africa when grown on calcareous soils. An evaluation of 3267 germplasm lines of kabuli-type chickpea for iron-deficiency chlorosis on the calcareous soil (calcium carbonate content 20%, pH8.5) of the principal research station of the International Centre for Agricultural Research in the Dry Areas (ICARDA) at Tel Hadya, northern Syria, revealed that most of the lines were tolerant while only 25 lines showed susceptibility. Foliar spray of 0.5% FeSO₄ at the onset of chlorosis was effective in correcting the symptoms but did not result in significant increase in crop yield.Studies on the inheritance of resistance to iron-deficiency chlorosis revealed that the resistance was dominant and is governed by a single gene.To ensure elimination from the breeding material of chickpea genotypes inefficient in Fe-use on the calcareous soils of the Mediterranean region, a negative selection for Fe-deficiency chlorosis in the segregating populations in the field has proved effective. The method for field screening of large number of breeding lines and germplasm is described.     

A physiological study ofTeucrium scorodonia ecotypes which differ in their susceptibility to lime-induced chlorosis and iron-deficiency chlorosis

Summary Edaphic ecotypes ofTeucrium scorodonia have been shown which differ in their susceptibility to lime-induced chlorosis. Plants especially resistant or susceptible to lime-induced chlorosis were found to be similarly resistant or susceptible to iron-deficiency chlorosis. Differences were found in the chlorophyll-iron and dry weight-chlorophyll relationships of the leaves of green and chloroticTeucrium plants, similar effects being produced by growth on a calcareous soil, in iron-deficient culture or by bicarbonate treatment. Chlorotic leaves had less chlorophyll per unit iron but had a greater dry weight per unit chlorophyll than green material. Chlorotic leaves were found to be reduced in both leaf area and dry weight compared with green ones, the reduction in dry weight being the greatest. Common root abnormalities were noted in chlorotic material induced by the above three methods.Evidence was produced which suggested that the difference between chlorosis-resistant and susceptible plants lay in qualitative differences in their iron transport compounds produced within the rootstock. Differential iron uptake was not suggested as a cause of the differences in behaviour. There was, however, evidence of a key role of the root iron pool in population differences in chlorosis susceptibility.Bicarbonate was found to suppress first iron uptake and then iron translocation. A possible causal role of the bicarbonate ion in lime-induced chlorosis was suggested through these effects and through its possible effect on the production of iron-transport compounds.     

Variability and correlation of iron-deficiency symptoms in a sorghum population evaluated in the field and growth chamber

Summary One hundred S₁ families from a random-mating sorghum [Sorghum bicolor (L.) Moench] population (NP21R) were rated visually for differences in iron-deficiency chlorosis in the field and in a growth chamber. Heritabilities on a family-mean basis were estimated for the first (0.63±0.15), maximum (0.79±0.15), and average chlorosis rating (0.84±0.15) recorded over S₁ families in the field. Heritability on an individual plant basis was estimated for the average chlorosis ratings in the growth chamber (0.65±0.16). Phenotypic and genotypic correlations were large and negative between field chlorosis ratings and yield or yield-related traits, which indicated that the severity of chlorosis was an important factor in determining S₁ family agronomic performance. Correlations between chlorosis traits over all S₁ families in the growth chamber and field generally were small and nonsignificant.     

Selection of olive varieties for tolerance to iron chlorosis

Under certain conditions, olive trees grown on calcareous soils suffer from iron chlorosis. In the present study several olive varieties and scion-rootstock combinations were evaluated for their tolerance to iron chlorosis. Plants were grown over several months in pots with a calcareous soil, under two fertilization treatments. These consisted of periodic applications of nutrient solutions containing either, 30 μmol/L FeEDDHA or not Fe. Tolerance was assessed by the chlorosis and growth parameters of plants grown without Fe, compared to those plants grown with Fe. Results show that there are differences in tolerance among olive varieties and that tolerance is mainly determined by the genotype of the rootstock. These results open the way to use tolerant varieties for those conditions where iron chlorosis could become a problem.     

Iron deficiency response in relation to iron uptake in two cultivars and a local strain ofMentha arvensisL.

The tolerance to iron-deficiency stress and the iron uptake were studied in two Japanese mint(Mentha arvensis L.) cultivars MAS1 and MS77 and their local strain MA2. A considerable reduction of pH of the nutrient medium in MAS1 and MS77 treatments associated with different degree of chlorosis was found. A rapid recovery from chlorosis was found only in MS77 and to some degree in MAS1, but not in the MA2. The results indicated that iron uptake and translocation were inversely related to iron stress tolerance.     

Iron availability in plant tissues-iron chlorosis on calcareous soils

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 Fe^III reduction brought about by a plasmalemma located Fe^III 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 Fe^III 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 Fe^III 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.     

缺铁胁迫下4种果树砧木中三价铁螯合物还原酶基因的表达

用活力染色法观测 4种果树砧木中FCR基因表达的结果表明 ,小金海棠 (M .xiaojinensis)和香橙 (C .junos)在缺铁胁迫下根吸收区FCR活性明显增强 ,增强幅度显著强于丽江山荆子 (M .rockii)和枳 (P .trifoliata)。用拟南芥的FCR基因 (FRO2 )做探针 ,进行组织印迹的RNANorthern杂交。结果表明 ,在缺铁胁迫下 ,在小金海棠和香橙中均有与FRO2类似基因的强烈表达 ,而在同样胁迫条件下的枳和丽江山荆子中表达却很微弱。这种分子水平上的反应与通常所熟知的生理反应是一致的 ,说明小金海棠和香橙忍耐缺铁环境的生理机制和分子基础类似 ,FCR在它们忍耐缺铁的生化反应中起着非常重要的作用 ,FCR基因在 4种果树砧木中的表达水平高低与它们忍耐缺铁的能力呈现正相关。并且 ,在小金海棠和香橙的根、茎、叶等营养器官的特定组织细胞中 ,均能检出高水平的FCR基因转录产物 ,表明耐缺铁能力强的小金海棠和香橙体内存在高效的铁运输和利用机制     

Differential susceptibility of two populations of Eucalyptus viminalis labill. to iron chlorosis

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.