可变电荷土壤和矿物Pb2+ and Cu2+吸附动力学: Ⅶ. Pb2+吸附后H+释放的动力学

The kinetics of H⁺ releasing after Pb²⁺ adsorption was studied by the potentiometric method combined with the acid-base titration curve technique. Results showed that pH of latosol, red soil and kaolinite suspensions dropped sharply, and then decreased gradually. Most of the H⁺ exchanged, more than 60%, was displaced at the first minute after Pb²⁺ was added into the suspension. More H⁺ was released at a higher concentration of Pb²⁺ added for a given sample and the amount of H⁺ released decreased in the order of red soil > latosol > kaolinite at a given concentration. The time-dependent data of H⁺ releasing of latosol, red soil and kaolinite at two concentrations could be fitted best with the second-order equation among the six equations, including second-order equation, two-constant equation, Elovich equation, parabolic diffusion equation, first-order equation and exponential equation. The H⁺/Pb²⁺ exchange stoichiometry increased with time, and a stable ratio of H⁺/Pb²⁺, being 1.73, 1.92 and 2.01 for kaolinite, latosol and red soil, respectively, was reached 25 minutes later.     

NO-3胁迫下K+、Ca2+对黄瓜幼苗膜质过氧化及活性氧清除酶系统的影响

通过水培试验探讨了NO^-₃胁迫下K⁺、Ca²⁺对黄瓜幼苗膜质过氧化及活性氧清除酶系统的影响。结果表明，在相同NO^-₃浓度胁迫7d后， Ca²⁺浓度越大，膜脂过氧化产物丙二醛(MDA)含量越高，而K⁺浓度越大，电解质相对渗透率越高，由此说明K⁺、Ca²⁺对细胞膜造成伤害的机理不同。黄瓜幼苗活性氧清除酶系统对K⁺、Ca²⁺的响应亦不同，在一定程度上，K⁺和Ca²⁺ 可提高SOD、POD和CAT活性，保护植物免受自由基伤害，继而可增强植物对逆境的适应能力。     

铁和不同形态氮素对玉米植株吸收矿质元素及其在体内分布的影响——Ⅰ.对氮、磷、钾、钙、镁等营养元素的影响

用营养液培养方法研究了铁和两种形态氮素(NO₃^--N和NH₄⁺-N)对玉米植株吸收氮、磷、钾等大量元素和钙、镁等中量元素及其在体内分布的影响。结果表明:与NO₃^--N相比,供应NH₄⁺-N促进了玉米对氮的吸收,在缺铁条件下,降低了对磷、钾、钙及镁的吸收。铁和NH₄⁺-N都显著提高了玉米植株各器官中氮的含量。与NH₄⁺-N处理相比,NO₃^--N处理的新叶中磷含量显著增加,但铁的供应对植物体内磷的含量无显著影响。使用NO₃^--N显著提高了玉米新叶和老叶中钾的含量,根和茎中钾的含量无明显影响。铁的供应降低了新叶和老叶中钾的含量。供铁时,NH₄⁺-N处理的玉米新叶中钙和镁的含量显著低于NO₃^--N处理,而在缺铁时则无显著差异。     

铁和不同形态氮素对玉米植株吸收矿质元素及其在体内分布的影响 Ⅱ.对铁、锰、铜、锌等营养元素的影响

用营养液培养方法研究了铁和两种形态氮素对玉米植株吸收铁、锰、铜、锌等微量元素及其在体内分布的影响。结果表明:与硝态氮(NO₃^--N)相比,铵态氮(NH₄⁺-N)显著提高了玉米对铁的吸收,降低了对锰、铜及锌的吸收。供铁也明显提高了植株地上部铁的吸收总量,降低了锰及锌的吸收量,尤其是在供应No₃^--N时这种作用更为明显。在缺铁条件下,NH₄⁺-N处理的玉米新叶中铁的含量明显高于NO₃^--N处理;而新叶、老叶、茎中锰、锌、铜含量以及根中锰、锌含量都明显低于NO₃^--N处理。但使用NH₄⁺-N时,根中铜的含量较高。在供铁条件下,NH₄⁺-N处理的玉米植株四个不同器官中锰和锌的含量显著低于NO₃^--N处理的植株,而铜的含量正好相反。在缺铁条件下,玉米新叶中活性锰、活性锌的含量显著高于供铁处理;与NO₃^--N相比,NH₄⁺-N的供应也显著降低了玉米新叶中活性锰以及活性锌的含量。     

宁夏引黄灌区稻田氮素浓度变化与迁移特征

过量施氮与不合理灌水是农田面源污染加剧的主要原因。为了寻求较优的水氮管理模式以促进农业生产和减少农田退水对黄河水体的污染, 在宁夏引黄灌区典型稻田中开展了不同水氮条件下稻田氮素迁移转化规律研究。结果表明: 不同水氮条件下稻田田面水NH₄⁺-N 与NO₃^--N 浓度伴随施肥出现明显峰值, NO₃^--N 峰值出现时间较NH₄⁺-N 晚, 且变化较平缓。3 次追肥时期和整个生育期田面水NH₄⁺-N 平均浓度与施氮量和灌水量都呈显著相关, 田面水NO₃^--N 平均浓度与施氮量呈显著正相关, 与灌水量相关性不显著。稻田30 cm与60 cm 深度的直渗水NH₄⁺-N 浓度受施肥影响较大, 与田面水NH₄⁺-N 浓度变化规律相似, 90 cm 处直渗水NH₄⁺-N 浓度峰值出现较为滞后, 且浓度较上层土体低, 120 cm 处直渗水NH₄⁺-N 浓度大体呈现持续上升趋势,整个生育期直渗水NH₄⁺-N 平均浓度与施氮量呈显著相关, 仅30 cm 处NH₄⁺-N 平均浓度与灌水量呈负相关, 其他土层深度不显著。30 cm 与60 cm 直渗水NO₃^--N 浓度在首次灌水后急剧下降, 在施肥后有较小幅度上升, 90 cm 与120 cm 直渗水NO₃^--N 浓度下降缓慢, 仅30 cm 处NO₃^--N 平均浓度与施肥量显著正相关。总的结果表明减少施肥或灌水均可达到减少农田氮素淋失的目的。     

不同土地利用方式土壤对铜、镉离子的吸附解吸特征

采用一次平衡法对Cu²⁺、Cd²⁺在城市及城郊农田、林地、草地3种土地利用方式土壤中的吸附解吸过程进行比较研究, 结果表明: Cu²⁺、Cd²⁺在3种土地利用方式土壤中的吸附量均随平衡液浓度的增加而增大, Cu²⁺、Cd²⁺在农田土壤上的吸附量均高于林地和草地土壤。分别用Langmuir和Freunlich两种等温吸附方程对吸附过程进行拟合, 3种土壤对Cu²⁺的吸附过程运用Langmuir方程拟合效果好, 而对Cd²⁺的吸附过程运用Freunlich方程拟合效果更好。Cu²⁺在3种土壤的解吸量大小顺序为农田>林地>草地, Cd²⁺在3种土壤的解吸量大小顺序为农田>草地>林地。两种离子在3种土壤中的动态吸附是个快速反应的过程, 随时间延长, 吸附反应趋于平衡。运用双常数函数方程和Elovich方程能较好地拟合重金属在土壤上的吸附动力学过程。Cu²⁺、Cd²⁺的吸附与土壤黏粒含量、有机质含量、CEC和pH均有关。     

La(NO3)3 对盐胁迫下黑麦草幼苗生长及抗逆生理特性的影响

为探讨稀土元素镧(La)对牧草盐胁迫伤害的缓解作用, 采用水培法研究了叶面喷施20 mg·L^-1La(NO₃)₃ 对NaCl 胁迫下黑麦草幼苗生长及其抗逆生理特性的影响。结果表明: 盐胁迫显著抑制黑麦草幼苗的生长, 提高叶片电解质渗漏率及丙二醛(MDA)、O₂^- 和H₂O₂ 含量, 其作用随盐浓度的增大而增强。超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性和抗坏血酸(AsA)、谷胱甘肽(GSH)、可溶性蛋白质、脯氨酸含量随盐浓度增大呈先升后降趋势, 可溶性糖和Na⁺/K⁺比逐渐增大, 质膜H⁺-ATP 酶活性逐渐降低, 过氧化物酶(POD)活性及POD 同功酶数量表达增强。喷施La(NO₃)₃ 处理可降低盐胁迫下黑麦草幼苗叶片的O₂^- 和H₂O₂ 含量, 提高SOD、CAT、POD、APX 和质膜H⁺-ATP 酶的活性及POD 同功酶的表达, 使AsA、GSH、可溶性蛋白质、可溶性糖和游离脯氨酸含量及幼苗生物量增加, Na⁺/K⁺比降低。表明La(NO₃)₃ 可通过提高抗氧化系统的活性和积累渗透溶质减轻盐胁迫伤害, 从而提高黑麦草的耐盐性。     

不同施肥条件下农田硝态氮迁移的试验研究

NO^-₃-N的淋失是旱地农田氮素损失的重要途径之一，也是引起地下水污染的一个主要原因。在黄土高原地区，夏玉米生长正逢雨季，是NO^-₃-N淋失的主要时期。该研究基于阻水层理论和黄土高原地区传统的垄作习惯，在手工模拟机具成垄压实施肥的基础上研究了该施肥法与传统的平地施肥、垄沟施肥(成垄不压实)条件下土壤NO^-₃-N的迁移动态，结果表明，在供水量相同条件下，由于平地和垄沟条件下水分分布的差异，导致平地土壤中的NO^-₃-N较垄沟耕作易于迁移。在生育前期，由于作物根系对NO^-₃-N的吸收和拦截，成垄压实与成垄不压实施肥对阻止NO^-₃-N随水下移差异不大；生育后期，当作物需肥量减小时，成垄压实施肥能够阻止NO^-₃-N向深层土壤迁移累积。玉米收获后，3种施肥方式下土壤NO^-₃-N迁移深度为平地(>60 cm)>垄沟施肥(>45 cm)>成垄压实施肥(＜35 cm)。     

含Ni六方水钠锰矿的表征及其对Pb 2+ (Zn2+)环境行为的影响

六方水钠锰矿是土壤中普遍存在、活性最强的氧化锰矿物。它常常富集各种过渡金属如Ni等,对其地球化学行为具有重要影响。在六方水钠锰矿形成过程中加入Ni²⁺,Ni以+2价存在于矿物中。进入水钠锰矿结构中的Ni大部分以[NiO₆ ]八面体形式存在于层内;仅有小部分Ni存在于八面体空位上下方。含Ni水钠锰矿沿c轴方向堆叠锰氧八面体层数逐渐减小,而a-b板面晶体大小没有明显变化,即层片状晶体逐渐变薄,比表面积显著增大。随着Ni含量的增加,水钠锰矿结构中锰氧八面体空位数减少,而层边面吸附位点数基本保持不变,其对重金属离子(Pb²⁺/Zn²⁺)吸附去除能力逐渐降低。本文为明确过渡金属离子(Ni)对土壤中氧化锰矿物的形貌、结构及其性质的影响提供了参考。     

SO42-和Cl-对稻田土壤养分及其吸附解吸特性的影响

利用长期定位试验 ,比较了长期施用含SO₄^2-和Cl^- 化肥 22年后稻田土壤的 pH值、养分状况及其吸附解吸特性。结果表明 ,长期施用含SO₄^2-化肥 ,土壤有机质、速效氮和速效钾的含量较高 ,但全量氮磷钾的含量较低 ;长期施用含Cl^- 化肥 ,土壤全量氮磷钾和速效磷的含量较高 ,但pH值相对较低。长期施用含上述二种阴离子的化肥后 ,土壤对H₂PO₄^-的最大吸附量均较大 ,且在Cl^- 处理下土壤对H₂PO₄^-吸附的结合能较大 ,而SO₄^2-处理下土壤在同等吸附量时对H₂PO₄^-的解吸量相应较多。长期施用含SO₄^2-的化肥亦使土壤对钾素的供应强度较大 (ΔK0的绝对值较大 )、缓冲能力增强 (AR0值较高 ) ,而长期施用含Cl^- 的化肥时则与SO₄^2-相反     

Iron deficiency stress responses amongst citrus rootstocks

Seedlings of citrus rootstocks differing in lime tolerance were grown in nutrient solution with and without Fe. Proton efflux, release of phenolic compounds and Fe reducing substances and root-mediated reduction of Fe^III in FeEDTA and freshly precipitated Fe(OH)₃ in response to Fe deficiency were determined. Sweet orange, Carrizo citrange and trifoliate orange, the three least tolerant rootstocks used in the study, did not decrease nutrient solution pH in response to Fe deficiency. The more lime tolerant rootstocks, rough lemon, Cleopatra mandarin and sour orange, did decrease nutrient solution pH. But in CaSO₄ solution only sour orange increased H⁺ efflux significantly under Fe deficiency. In response to Fe deficiency, the release of phenolic compounds was increased significantly in rough lemon and Cleopatra mandarin seedlings, while the release of reducing substances was increased significantly in rough lemon, sour orange and trifoliate orange. Rough lemon was the only rootstock to respond to Fe deficiency with an increase in root-mediated reduction of chelated Fe^III at pH 6.5. At pH 8.0, both Fe-deficient rough lemon and Cleopatra mandarin roots reduced higher amounts of Fe^III from freshly precipitated Fe(OH)₃ than Fe-sufficient seedlings. Iron reduction by detached roots of Fe-deficient and Fe-sufficient rough lemon did not follow Michaelis-Menten kinetics at high substrate concentrations. Rates of Fe reduction at low substrate concentrations were inconsistent with the existence of an inducible ferric reductase in response to Fe deficiency.     

Chelation effects on the iron reduction and uptake by low‐iron stress tolerant and non‐tolerant citrus rootstocks

The relative rates of ferric‐iron (Fe³⁺) reduction and uptake by two citrus rootstocks were measured for a series of synthetic Fe³⁺ chelates and microbial siderophores. The rates of Fe³⁺ reduction by the citrus seedlings followed the order: FeHEDTA >> FeDPTA > FeCDTA. No reduction occurred for FeDFOB (ferrioxamine B) and FeTAF (ferric triacetylfusagen). Low rates of Fe³⁺ reduction occurred for Fe2RA3 (ferric rhodotorulic acid). The levels of ⁵⁵Fe taken up the citrus seedlings showed good correlations with the reduction rates. These results indicate the importance of Fe³⁺ reduction in the Fe uptake by citrus rootstocks. The immobility of a large percent of the ⁵⁵Fe taken up by the roots is attributed to the accumulation of Fe in the root apoplasts.     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. I. Effect on iron nutrition and iron stress response

Cool white fluorescent (CWF) light reduces Fe³⁺ to Fe²⁺ while low pressure sodium (LPS) light does not. Cotton plants grown under CWF light are green, while those yrown under LPS light develop a chlorosis very similar to the chlorosis that develops when the plants are deficient in iron (Fe). It could be that CWF light (which has ultra violet) makes iron more available for plant use by maintaining more Fe²⁺ in the plant. Two of the factors commonly induced by Fe‐stress in dicotyledonous plants‐‐hydroyen ions and reductants released by the roots‐‐were measured as indicators of the Fe‐deficiency stress response mechanism in M8 cotton.

The plants were grown under LPS and CWF light in nutrient solutions containing either NO₃‐N or NH₄‐N as the source of nitrogen, and also in a fertilized alkaline soil. Leaf chlorophyll concentration varied significantly in plants grown under the two light sources as follows: CWF+Fe > LPS+Fe > CWF‐Fe ≥ LPS‐Fe. The leaf nitrate and root Fe concentrations were significantly greater and leaf Fe was generally lower in plants grown under LPS than CWF light. Hydrogen ions were extruded by Fe‐deficiency stressed roots grown under either LPS or CWF light, but “reductants”; were extruded only by the plants grown under CWF light. In tests demonstrating the ability of light to reduce Fe³⁺ to Fe²⁺ in solutions, enough ultra violet penetrated the chlorotic leaf of LPS yrown plants to reduce some Fe³⁺ in a beaker below, but no reduction was evident through a yreen CWF grown leaf.

The chlorosis that developed in these cotton plants appeared to be induced by a response to the source of liyht and not by the fertilizer added. It seems possible that ultra violet liyht could affect the reduction of Fe³⁺ to Fe²⁺ in leaves and thus control the availability of this iron to biological systems requiring iron in the plant.     

An iron chelating compound released by barley roots in response to Fe‐deficiency stress

The excretion of phytosiderophores by barley (Hordeum vulgare L.) has recently been documented and a major difference in the Fe‐stress response of gramineous species and dicotyledonous species proposed. However, currently used methods of quantifying and measuring phytosiderophore are tedious or require specialized equipment and a cultivar easily accessible to U.S. scientists is needed. The objectives of this study were (a) to determine if “Steptoe”; and “Europa”; (used as a control cultivar) barleys would release Fe³⁺ solubilizing compounds in response to Fe‐deficiency stress and (b) to develop a technique to determine the efficiency of solubilization of Fe(OH)₃ by the released chelating substances. Two cultivars of barley were place under Fe‐stressed (‐Fe) and nonstressed (+Fe) conditions in modified Hoagland solutions (14 L). The solutions were periodically monitored for H⁺ and reductant release from the roots and plants were rated daily for chlorosis development. Periodic (6 or 7 harvests) evaluation of the release of Fe³⁺ solubilizing substances was performed as herein described. Neither H⁺ nor reductant extrusion occurred with either cultivar during Fe stress. However, Fe³⁺ solubilizing substances were released by both cultivars at relatively high levels under Fe‐stress conditions compared to the nonstressed plants. A convenient technique was developed to measure the release of Fe solubilizing substances released by barley roots.     

铁肥根系输液矫正果树缺铁失绿症机理

邻二氮杂啡铁示踪结果表明 ,铁肥根系输液处理时铁以二价态由根被动吸收 ,并运输到根、茎、和叶的主脉内。运输部位都是靠近形成层的木质部 ,运输速度每小时可达数十厘米。室内营养液培养的八棱海棠苗用59Fe示踪结果表明 ,断根中分配的59Fe为 18.1% ,叶中分配的59Fe占 70 .9% ;断 1、2、3条根的植株59Fe在叶中的分配比例分别为 57.9%、63.6 %、68.0 %。     

Root responses of sterile‐grown onion plants to iron deficiency 1

Onion (Allium sativum) plants grown without iron (Fe) in sterile nutrient solutions readily developed chlorosis symptoms. Iron deficiency in the sterile‐grown plants stimulated the rates of root extracellular reduction of Fe³⁺, copper (Cu²⁺), manganese (Mn⁴⁺), and other artificial electron acceptors. While rapid reduction occurred with the synthetic chelate Fe³⁺HEDTA, no short‐term reduction occurred with the fungal siderophore Fe³⁺ferrioxamine B (FeFOB). In addition to the increased rate of extracellular electron transfer at the root surfaces, the Fe‐deficient plants showed greater rates of Fe uptake and translocation than the onion plants grown with Fe. The rates of uptake and translocation of Fe were sharply higher for the Fe‐deficient plants supplied with FeHEDTA than for similar plants supplied with FeFOB. Inhibition by BPDS of the Fe uptake by the Fe‐deficient onion plants further supported the importance of Fe³⁺ chelate reduction for the uptake of Fe into the roots. Rates of Fe uptake and translocation by Fe‐deficient onion plants supplied with ⁵⁵FeFOB were identical to the rates of uptake of ferrated [14C]‐FOD; a result that gives evidence of the uptake and translocation of the intact ferrated siderophore, presumably by a mechanism not involving prior extracellular Fe³⁺ reduction. Differences in the rates of transport of other micronutrients into the roots of the Fe‐deficient onion plants were evident by the significantly higher Zn and Mn levels in the shoots of the Fe‐deficient onion.     

Iron deficiency studies of sugar beet using an improved sodium bicarbonate‐buffered hydroponic growth system

A sodium bicarbonate (NaHCO₃)‐buffered hydroponic growth system was developed that simulates alkaline soil growth conditions necessary to screen sugar beet genotypes for iron (Fe) efficiency character. Three genotypes (NB1, NB4, and F, hybrid, NB 1xNB4) with differing capacities for Strategy I Fe responses were phenotyped successfully using this system. Genotypes NB1 and NB1xNB4 are Fe efficient, while NB4 is Fe inefficient. It was demonstrated that 5 mM NaHCO₃ provided buffering within an optimal range (pH 7.3 ‐ pH 6.3) for the duration of ‐Fe treatments, promoted enhanced H⁺ extrusion, and increased the in vivo capacity for Fe³⁺‐chelate reduction (Fe³⁺‐chelate reductase [FCR] activity), especially in the roots of the Fe efficient genotypes. The same concentrations of NaHCO₃ did not interfere with Fe supply to +Fe control plants of any genotype. The in vivo capacity for Fe³⁺‐chelate reduction increased over fivefold in both Fe efficient genotypes (NB1 and NB 1xNB4), but just under twofold in the Fe inefficient genotype (NB4). Localization and duration of enhanced Fe³⁺‐chelate reduction capacity were dependent upon the Fe efficiency character of each genotype.     

Plant Uptake of Iron Chelated by Humic Acids of Different Molecular Weights

Abstract

Mobilization of iron (Fe) chelated by humic acids (HA) of low (HA_10,000) and high molecular weight (HA_100,000) fractions and its uptake by plants were investigated in growth experiments with sunflower seedlings. The iron chelates (labeled with ⁵⁹Fe) contained in dialysis bags (mw. cutoff=3500) were placed in minus iron Hoagland solutions as the Fe source and at the same time fulvic acid (FA), EDTA, and low and high molecular weight HA fractions were added in the solutions as mobilizators. Characterization of FA, HA_10,000, and HA_100,000 were performed by infrared spectroscopy and chemical analysis, e.g., total acidity, COOH, and phenolic‐OH content. Roots and leaves were harvested, dried, and ground for Fe activity determination. Iron contents and pH in the nutrient solutions were measured before and after treatments. The supply of Fe to the plants was apparently sufficient, because no Fe deficiency has been detected in the test plants but during the whole absorption period, the pH of the nutrient solution was about 4.5. The Fe contents in leaves indicated that part of the Fe was rapidly transported from roots to leaves. Judging from the Fe contents in leaves, it was assumed that the small size HA_10,000 and EDTA were the most efficient in affecting transport of Fe from root to leaf tissue. FA, HA_10,000, and especially HA_100,000 were unable to penetrate the dialysis bags and, hence, were effective in Fe mobilization only after the Fe, dissociated from the Fe‐HA chelate, has passed the dialysis membrane into the nutrient solutions. In contrast, the small size EDTA was expected to have penetrated the dialysis bags, permitting mobilization of chelated Fe by ligand exchange inside the bags, and transporting the Fe to the roots. The results suggested that the humic substances used in this study were able to form with the Fe³⁺ ion complexes that maintained the iron available to the sunflower plants. In the chemical form of Fe.L, where L was FA o HA, the iron within the bags or in solution or in the roots free space, was available for exchange reactions with the natural sunflower plant chelators for its transport to the leaves.     

Factors in iron‐stress response mechanism enhanced by Zn‐deficiency stress in Sanilac,but not Saginaw navy bean

Zinc‐inefficient Sanilac and Zn‐efficient Saginaw navy bean (Phaseolus vulgaris L.) differ in their susceptibility to Zn‐deficiency stress. Sanilac accumulates Fe under Zn‐deficiency stress and Saginaw does not. These two navy bean cultivars were grown at 0, 0.006 and 0.12 mg/L Zn in modified Hoagland nutrient solution. Various Fe‐stress response mechanisms were quantified periodically over a 12‐day experimental period to determine if known factors in the Fe‐stress response mechanism were enhanced by Zn‐deficiency stress. Visual Zn‐deficiency symptoms were more severe in Sanilac than Saginaw navy bean under equivalent Zn treatments. Sanilac contained lower leaf Zn than Saginaw when Zn was present in solution (0.006 and 0.12 mg/L Zn), but the two cultivars were similar in leaf Zn in the absence of Zn (0 mg/L Zn). Sanilac accumulated more leaf Fe than Saginaw when under Zn stress (0 and 0.006 mg/L Zn). The higher levels of leaf Fe in Sanilac than Saginaw were closely associated with enhanced release of reductants and increased reduction of Fe³⁺ to Fe²⁺ by roots of Sanilac. Saginaw navy bean roots reduced Fe³⁺ to Fe²⁺ similarly to Sanilac with adequate Zn present in solution (0.12 mg/L), but experienced minuscule levels of Fe³⁺ reduction under Zn deficiency. Zinc deficiency stimulated the initiation of the Fe‐stress response mechanism in Sanilac, but not Saginaw, which may have enhanced the development of Zn‐deficiency symptoms in Sanilac due to the increased uptake of Fe by this cultivar. The common Fe‐deficiency stress response associated primarily with grasses (release of phytosiderophore) was not found in either navy bean cultivar.     

Effects of exogenous SA supplied with different approaches on growth,chlorophyll content and antioxidant enzymes of peanut growing on calcareous soil

To assess the role of salicylic acid (SA) supplied with 5 approaches in alleviating chlorosis induced by iron (Fe) deficiency in peanut plants growing on calcareous soil, SA was supplied as soil incorporation, making slow-release particles, seed soaking, irrigation and foliar application. SA application, particularly, SA supplied by slow release particles, dramatically increased growth parameters, yield and quality of peanut, and increased Fe concentration in peanut grain. Meanwhile, SA application increased the H⁺-ATPase activity, reduced pH of soil, increased Fe³⁺-Chelate Reductase (FCR) activity in roots, and increased Fe concentration in roots. Furthermore, SA increased active Fe content and increased chlorophyll content. In addition, SA improved enzymes activities containing superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and protected Fe deficiency induced oxidative stress. Therefore, SA has a good effect on alleviating chlorosis induced by Fe deficiency on calcareous soil. However, in the 5 SA supplied approaches, foliar application and making slow release particles were more effective.