Effects of root addition and foliar application of nitric oxide and salicylic acid in alleviating iron deficiency induced chlorosis of peanut seedlings

Nitric oxide (NO) and salicylic acid (SA) are two important signaling molecules, which could alleviate chlorosis of peanut under iron (Fe) deficiency. Here, we further investigated the mechanism of different combinations of sodium nitroprusside (SNP, a nitric oxide donor) and SA supplying in alleviation Fe deficiency symptoms and selected which is the best combination. Thus, peanut was cultivated in hydroponic culture under iron limiting condition with different combinations of SNP and SA application. After 21 days, Fe deficiency significantly inhibited peanut growth, decreased soluble Fe concentration and chlorophyll contents, and disturbed ionic homeostasis. In addition, the content of reactive oxygen species (ROS) and malondialdehyde (MDA) concentration increased, which led the lipid peroxidation. Application of SNP and SA significantly changed Fe trafficking in cells and organs, which increased Fe uptake from nutrient solution, and transport from root to shoot, enhanced the activity of ferric-chelate reductase (FCR), that increased the available Fe in cell organelles, and the active Fe, chlorophyll contents in leaves. Furthermore, ameliorated the inhibition of calcium (Ca), magnesium (Mg) and zinc (Zn) uptake and promoted plant growth in Fe deficiency. At the same time, it increased the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) to protect the plasmolemma from peroxidation. Results demonstrated that different combinations of SNP and SA application could alleviate the chlorosis of peanut in Fe deficiency by various mechanisms. Such as increased the available Fe and chlorophyll concentrations in leaves, improved the activities of antioxidant enzymes and modulated the mineral elements balance and so on. Foliar application of SNP and SA is the best to protect leaves while directly adding them into nutrient solution is the best to protect roots. These results also indicated that the effects of SNP and SA supplying together to leaves or roots are better than respectively adding to roots and spraying to leaves. The best combination is foliar application of SNP and SA.     

Mechanisms of exogenous nitric oxide and 24-epibrassinolide alleviating chlorosis of peanut plants under iron deficiency

Iron(Fe) is a crucial transition metal for all living organisms including plants; however, Fe deficiency frequently occurs in plant because only a small portion of Fe is bioavailable in soil in recent years. To cope with Fe deficiency, plants have evolved a wide range of adaptive responses from changes in morphology to altered physiology. To understand the role of nitric oxide(NO) and 24-epibrassinolide(EBR) in alleviating chlorosis induced by Fe deficiency in peanut(Arachis hypogaea L.) plants, we determined the concentration of chlorophylls, the activation, uptake, and translocation of Fe, the activities of key enzymes, such as ferric-chelate reductase(FCR),proton-translocating adenosine triphosphatase(H~+-ATPase), and antioxidant enzymes, and the accumulation of reactive oxygen species(ROS) and malondialdehyde(MDA) of peanut plants under Fe sufficiency(100 μmol L~(-1)ethylenediaminetetraacetic acid(EDTA)-Fe) and Fe deficiency(0 μmol L~(-1)EDTA-Fe). We also investigated the production of NO in peanut plants subjected to Fe deficiency with foliar application of sodium nitroprusside(SNP), a donor of NO, and/or EBR. The results showed that Fe deficiency resulted in severe chlorosis and oxidative stress, significantly decreased the concentration of chlorophylls and active Fe, and significantly increased NO production. Foliar application of NO and/or EBR increased the activity of antioxidant enzymes, superoxide dismutase,peroxidase, and catalase, and decreased the ROS and MDA concentrations, thus enhancing the resistance of plants to oxidative stress.Application of NO also significantly increased Fe translocation from the roots to the shoots and enhanced the transfer of Fe from the cell wall fraction to the cell organelle and soluble fractions. Consequently, the concentrations of available Fe and chlorophylls in the leaves were elevated. Furthermore, the activities of H~+-ATPase and FCR were enhanced in the Fe-deficient plants. Simultaneously,there was a significant increase in NO production, especially in the plants that received NO, regardless of Fe supply. These suggest that NO or EBR, and, especially, their combination are effective in alleviating plant chlorosis induced by Fe deficiency.     

Effects of Nitric Oxide on Iron-Deficiency Stress Alleviation of Peanut

The aim of this research was to study the role of nitric oxide (NO) in alleviating iron deficiency induced chlorosis of peanut (Arachis hypogaea L.). For this study, sodium nitroprusside (SNP) was used to supply NO for hydroponic peanut plants. After 18 days, the peanut seedlings growing without iron exhibited significant leaf interveinal chlorosis, and this iron-deficiency induced symptom was completely prevented by NO. An increased content of chlorophyll and active iron was observed in NO-treated young leaves, suggesting an improvement of iron availability in plants. In addition, the improved rhizosphere acidification and increased secretion of organic acids by root in NO-treated plants suggesting that NO is effective in modulating iron uptake and transport inside the peanut plants. Furthermore, NO treatment alleviated the increased accumulation of superoxide anion (O₂^??) and malondialdehyde (MDA), and modulated the antioxidant enzymes. However, the SNP with a prior sunlight treatment that does not release NO had no significant effect on the chlorophyll levels in iron-deficient plants. Therefore, these results support a physiological action of NO on the availability, uptake and transport of iron in the plant.     

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.     

Application of Exogenous Sodium Nitroprussid Alleviates Boron Toxicity in Wheat Seedlings: Investigation of Thiol Compounds,Macro/Micronutrient,and Polyamine Contents

High boron (B) levels in the soil reduce plant growth and yield production in crop plants. Nitric oxide (NO) is a highly reactive signaling molecule involved in stress response in plants. The aim of the study was to investigate the role of sodium nitroprussid (SNP), a NO donor, in alleviating the B-induced toxicity in two wheat cultivars. Both cultivars were treated with 10 mM B, 10 mM B + 0.1 mM SNP, 10 mM B + 0.2 mM SNP, and 10 mM B + 0.5 mM SNP. The nutrient contents were investigated via inductively coupled plasma mass-spectrometry. Contents of polyamines and thiol compounds were analyzed by high-performance liquid chromatography. The B toxicity caused a significant decrease in nutrient contents and thiol compounds, but increased polyamine contents. However, exogenous application of 0.2 mM SNP increased nutrient contents and thiol compounds, but lowered polyamine contents. The study clearly revealed that exogenous SNP can overcome the toxic effects of B on wheat seedlings.     

Exogenous Nitric Oxide Effects on Physiological Characteristics of a Peanut Cultivar Growing on Calcareous Soil

This study examined the effects of exogenous nitric oxide (NO) on physiological characteristics of peanut (Arachis hypogaea L.) growing on calcareous soil. Sodium nitroprusside (SNP) was added into slow-release fertilizer (SRF) or sprayed on leaves to supply NO for iron-deficient peanut. The results showed that root application of SNP at 5.63 mg/g and foliar spray of SNP at 1.0 mmol L^?1 significantly enhanced the peanut growth, pod yield, and quality. The soil pH was reduced, and available iron content and iron (Fe³⁺) reductase activity in root were increased, indicating NO application improved the availability of iron in the soil. Additionally, NO increased the chlorophyll and active iron content in young leaves, implying NO enhanced the availability of iron within the plant. Nitric oxide also inhibited the malondialdehyde (MDA) accumulation in leaves and increased the activity of antioxidant enzymes, which protected peanut against iron-deficiency-induced oxidative stress. It was concluded that NO might be employed for ameliorating iron-deficient chlorosis of peanut on calcareous soil when added into SRF or sprayed on leaves.     

Effects of Exogenous Nitric Oxide and 24-Epibrassinolide on the Physiological Characteristics of Peanut Seedlings Under Cadmium Stress

Cadmium(Cd) is highly toxic to plants, animals, and humans. Limited information is available on the role of nitric oxide(NO)and/or 24-epibrassinolide(EBR) in response of plants to Cd stress. In this study, a hydroponic experiment was performed to investigate the effects of NO and/or EBR on peanut plants subjected to Cd stress(200 μmol L~(-1)) with sodium nitroprusside(SNP, an exogenous NO donor)(250 μmol L~(-1)) and/or EBR(0.1 μmol L~(-1)) addition. The results showed that Cd exposure inhibited plant growth, and this stress was alleviated by exogenous NO or EBR, and especially the combination of the two. Treatment with Cd inhibited the growth of peanut seedlings, decreased chlorophyll content, and significantly increased the Cd concentration in plants. Furthermore, the concentration of reactive oxygen species(ROS) markedly increased in peanut seedlings under Cd stress, resulting in the accumulation of malondialdehyde(MDA) and proline in leaves and roots. Under Cd stress, applications of SNP, EBR, and especially the two in combination significantly reduced the translocation of Cd from roots to leaves, increased the chlorophyll content, decreased the concentrations of ROS, MDA, and proline, and significantly enhanced the activities of superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) in peanut seedlings. Exogenous NO and/or EBR also stimulated the activities of nitrate reductase(NR)and nitric oxide synthase(NOS) and increased the contents of antioxidants, such as ascorbic acid(AsA) and reduced glutathione(GSH). Furthermore, exogenous NO and/or EBR enhanced Cd accumulation in the cell wall and thus decreased Cd distribution in the organelles in the roots. The concentrations of calcium(Ca), iron(Fe), magnesium(Mg), and zinc(Zn) were also regulated by exogenous NO or EBR, and especially by the two in combination. These results indicated that SNP and EBR, alone and particularly in combination, can mitigate the negative effects of Cd stress in peanut plants.     

外源NO对缺铁胁迫下花生生理特性的影响

为探讨外源NO对缺铁胁迫下花生生理特性的影响,采用溶液培养方法,研究了营养液中Fe(Ⅲ)-EDTA 浓度分别为0、10、100 mol/L 条件下,外施250 mol/L硝普钠（SNP, 一种NO 供体）对花生生理特性以及矿质元素含量的影响。结果表明,在相同供铁水平下,外施NO可促进花生幼苗的生长,提高根系活力、净光合速率、蒸腾速率、气孔导度和叶片抗氧化酶活性,降低胞间CO2 浓度和MDA 含量,抑制花生对P 的吸收;在Fe(Ⅲ)-EDTA 浓度分别为0、10 mol/L 条件下综合效果更显著。在0、10、100 mol/L Fe(Ⅲ)-EDTA 中施加SNP 处理20d 后,叶片活性铁含量分别比未施加SNP处理提高了130.7%、136.4%、56.1%,差异显著;同时植株全铁含量及地上部吸铁量占植株总量的百分率也显著提高。说明外源NO可促进铁从根部向植株地上部的运输以及植株体内铁的有效性,提高了铁的运输和利用效率,有效缓解缺铁胁迫的抑制。同时,外施NO还可提高花生叶片叶绿素、类胡萝卜素含量和叶绿素a/b值。在Fe(Ⅲ)-EDTA 浓度分别为0、10 mol/L 条件下,添加SNP 可以明显降低生长介质的pH,比较 1d 内生长介质中pH 变化看出,花生在14h左右分泌H+ 的能力最强。     

Effectiveness of salicylic acid in mitigating salt-induced adverse effects on different physio-biochemical attributes in sweet basil (Ocimum basilicum L.)

The objective of this study was to determine the effects of foliar salicylic acid (SA) on salt tolerance of sweet basil seedlings by examining growth, photosynthetic activity, total osmoregulators, and mineral content under salinity. Salinity treatments were established by adding 0, 60, and 120 mM sodium chloride (NaCl) to a base nutrient solution. The addition of 60 and 120 mM NaCl inhibited the growth, photosynthetic activity, and nutrient uptake of sweet basil seedlings, and increased the electrolyte leakage and the plant contents of proline and Na. Sweet basil seedlings were treated with foliar SA application at different concentrations (0.0, 0.50, and 1.00 mM). Foliar applications of SA led to an increase in the growth, chlorophyll content, and gas exchange attributes. With regard to nutrient content, it can be inferred that foliar SA applications increased almost all nutrient content in leaves of sweet basil plants under salt stress. Generally, the greatest values were obtained from 1.00 mM SA application.     

外源NO对盐胁迫下小麦幼苗生长及生理特性的影响

在盆栽试验条件下,以冬小麦(山农22)为供试材料,以硝普钠(SNP)为外源一氧化氮(NO)供体,研究了3种施用方式的外源NO对盐胁迫下小麦幼苗生长及生理特性的影响。试验共设5个处理:对照(CK)、氮磷钾(NPK)肥(T1)、NPK肥+SNP浸种(T2)、NPK肥+SNP粉末施入土壤(T3)和NPK肥+SNP缓释颗粒施入土壤(T4)。结果表明:盐胁迫条件下,小麦植株体内会积累大量的活性氧,抑制了小麦幼苗的生长;T1-T4处理的小麦幼苗长势均优于CK。与T1处理相比,添加外源NO的T2-T4处理均可显著提高小麦出苗率,其中以T4效果最为显著,可显著促进小麦幼苗的生长,提高叶片鲜重、叶片干重、叶绿素含量及抗氧化酶活性,降低叶片中超氧阴离子产生速率及过氧化氢含量,减少小麦幼苗对Na+的吸收,增加K+的吸收,维持小麦体内Na+、K+平衡,并促进根系对N、P元素的吸收,从而保证小麦植株养分吸收平衡。因此,添加外源NO既能通过促进幼苗生长、提高抗氧化酶活性、调节离子平衡等途径来提高小麦幼苗的抗盐性,缓解盐胁迫对小麦幼苗的伤害,又能通过调节根系对营养元素的吸收来促进小麦幼苗的生长。且在3种不同的SNP施用方式中,以SNP制成缓释颗粒施入土壤的施用方式对小麦盐胁迫的缓解效果最优。     

Effects of exogenously applied salicylic acid on the induction of multiple stress tolerance and mineral nutrition in maize (Zea mays L.)

Abstract

It has been proposed that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing environmental stress tolerance in plants. In this study, the effects of seed soaked (1.0 mM for 24 h) and soil incorporated (0.1 mM and 0.5 mM) salicylic acid (SA) supply on growth and mineral concentrations of maize (Zea mays L., Hamidiye F₁) grown under either salt, boron toxicity or drought-stressed conditions were investigated. Exogenously applied SA either with seed soaked (SS) or soil incorporated (SI) increased plant growth significantly in all the stresses conditions. Salicylic acid inhibited Na and Cl accumulation in saline conditions, and 0.5 mM of soil incorporated SA decreased B significantly in boron toxicity treatment. Except in drought condition, SA treatments stimulated N accumulation in plants. And P, K, Mg and Mn concentrations of SA received plants were increased in the stress conditions. These results suggest that SA regulates the response of plants to the environmental stresses and could be used as a plant growth regulator to improve plant growth and stimulate mineral nutrient concentrations under stress conditions.     

Salicylic Acid–Induced Salinity Redressal in Hydroponically Grown Strawberry

The present study was conducted to evaluate shoot and root mineral composition of salt-stressed Selva strawberry under application timing of salicylic acid (SA). Treatments included plants sprayed with 0.5 or 1 mM SA, plants exposed to 40 mM sodium chloride (NaCl), and plants sprayed with 0.5 or 1 mM SA 1 week before, simultaneously, or after initiation of 40 mM salinity. Results indicated that under saline conditions, sodium (Na) and chloride (Cl) contents increased along with decrease in nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn) in shoot and root of plants. In plants treated with SA at 1 mM concentration, 1 week before salinity application, root Mg and shoot Ca were greater in comparison to salt-stressed plants treated with the same SA concentration 1 week after their exposure to salt stress. Thus, earlier SA application appears to be a better strategy for optimized protection against deleterious influence of salinity.     

Determination of Fe2+ in Rice Leaves (Oryza sativa L.) by Using the Chelator BPDS Alone or Combined with the Chelator EDTA

Abstract

Iron toxicity is a problem in many areas of wetland rice. Since Fe²⁺ is considered to be the toxic form of iron, the objective of this research was to determine the Fe²⁺ concentration in rice leaves using the chelator bathophenanthroline disulfonate (BPDS), disodium salt alone or combined with the chelator ethylenediaminetetraacetate (EDTA), disodium salt, where BPDS should solely chelate the Fe²⁺ and EDTA chelate only Fe³⁺. Thus, the combination of these chelators should stabilize the Fe oxidation states. It was also tested whether the chelators BPDS and EDTA could stabilize the oxidation states of Fe during the extraction of rice leaves. Extractions of rice leaves were carried out using an 1 mM BPDS or BPDS‐EDTA extractant solution. To test the stabilization of the Fe oxidation states by the combination of BPDS with EDTA, the extraction solution for one part of the samples contained 0.07 mM Fe³⁺. An extraction without plant material as control was also taken into consideration. The results indicated that the chelators were able to stabilize the oxidation states of Fe in the control (extraction without plant material). However, in the presence of plant material, Fe³⁺ was partly reduced to Fe²⁺, i.e., the chelators could not stabilize the oxidation states of Fe. Accordingly, we concluded that the BPDS‐EDTA method may function for the Fe²⁺ determination in water and soil, but it is apparently not suited for rice leaves.     

Two cultivars of peanut (Arachis hypogaea) seedlings show different tolerance to calcium deficiency

The objectives were to determine whether two peanut cultivars show different tolerance to calcium (Ca) deficiency. The seedlings of cultivars LH11 and YZ9102 at first trifoliate leaf stage were transplanted in nutrient solution for 28 days with 0.01 and 2.0 mmol/L Ca treatments. Low Ca supply did not affect plant growth, root length and surface area of YZ9102, whereas decreased plant biomass, root length and surface area of LH11 seedlings that appeared necrosis in shoot tip. YZ9102 plant had higher Ca concentration and more Ca distribution to leaves than LH11. Under limited Ca condition, LH11 appeared net Ca²⁺ effluxes in the zones of 0.2 ～ 1.5 mm from root apex, while YZ9102 roots maintained net Ca²⁺ influxes. Peanut cultivar YZ9102 seedlings had longer roots and higher capacities of Ca uptake and Ca translocation to shoots than LH11, which might be account for higher tolerance to Ca deficiency compared with LH11.     

VEGETATIVE GROWTH,YIELD, FRUIT QUALITY AND FRUIT AND LEAF COMPOSITION OF STRAWBERRY CV. ‘PAJARO’ AS INFLUENCED BY SALICYLIC ACID AND NICKEL SPRAYS

Salicylic acid (SA) occurs naturally in plants at low concentrations. Previous studies reported a vast range of responses after SA application on plants. Nickel (Ni) as an essential element for plant growth and development has been proven to have positive impact on overall plant life cycle. To evaluate influence of these two compounds on strawberry plants cv. ‘Pajero’ this study was carried out as a 3 × 4 factorial in a completely randomized design in greenhouse conditions. Treatments included SA at 0, 1, 2, and 3 mM and nickel sulfate (NiSO₄) at 0, 150 and 300 mg L^?1 concentration. It seems that treatments had promoting effects on measured parameters as 2 mM of SA increased root and shoot fresh and dry weight, concentration of anthocyanins and poliphenolics of fruits significantly, 3 mM of this phytohormone caused augmentation of vitamin C content of fruits. Nitrogen and nickel concentration within leaves and fruits were affected after SA treatments. 150 mg L^?1 of nickel solution promoted total yield, root dry weight and nitrogen concentration of fruits. Worth mentioning, beneficial effects of such treatments were higher when applied together. Further research is needed before recommendation on other cultivars and commercial use.     

Differences in Response to Iron Deficiency Among Some Lines of Common Bean

Abstract

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29‐21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root‐associated Fe³⁺‐reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 µM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe‐chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29‐21 and, particularly, ARA14 plants. However, all Fe‐sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl₂. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root‐associated Fe(III)‐reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.     

Effect of application of exogenous nitric oxide at different critical growth stages in alleviating Fe deficiency chlorosis of peanut growing in calcareous soil

This study was to investigate peanut response to application of nitric oxide (NO) at different growth stages and the effects of NO application on peanut yield and quality in calcareous soil. Sodium nitroprusside (SNP, a NO donor) solution was poured into calcareous soil at sowing, seedling, flowering, and podding stages, respectively, or at each aforesaid critical stage. Results showed that NO application increased the content of active Fe and leaf chlorophyll, which improved the photosynthesis of peanut; enhanced the ability of resistance to oxidative stress by decreased the accumulation of O₂^??, H₂O₂, and MDA and increased the activity of antioxidant enzymes. Nitric oxide increased the content of soil available Fe and root FCR activity, which can promote peanut absorb more Fe from the calcareous soil. What's more, peanut plants may pump a large amount of H⁺ from root cell membrane to consume in neutralization of HCO₃^?, and decrease the pH in apoplast, cytoplasm, and xylem, finally balance the mineral elements (Fe, Ca, Mg, Zn, and Cu) uptake and distribution. These results indicated that NO could improve peanut growth and development, increase peanut yield and quality. Furthermore, the application of NO at sowing or seedling stage did the most obvious effect on alleviating chlorosis of peanut in calcareous soil.     

Nitric oxide improves high zinc tolerance in maize plants

A short-term experiment was carried out to study the effects of exogenous nitric oxide (NO) on some growth parameters and mineral nutrients of maize grown at high zinc (Zn). Maize seedlings were planted in pots containing perlite and subjected to 0.05 or 0.5 mM Zn in nutrient solution. Nitric oxide (0.1 mM) was sprayed to the leaves of maize seedlings. High Zn reduced total dry matter, chlorophyll (Chl.) content and leaf relative water content (RWC), but increased proline content and membrane permeability. Foliar application of NO significantly increased chlorophyll content, RWC and growth of plants treated with high Zn, and significantly reduced their membrane permeability and proline contents. High Zn resulted in increased leaf and root Zn, but lower concentrations of leaf phosphorus (P), and iron (Fe). Foliar application of NO lowered leaf and root Zn and increased leaf and root nitrogen (N) and leaf Fe in the high Zn plants. These results clearly demonstrated that externally-applied NO induced growth improvement in maize plants was found to be associated with reduced membrane permeability under high zinc. Results can be concluded that NO may be involved in nutritional and physiological changes in plants subjected to high Zn.     

Partitioning of Newly Absorbed and Previously Stored Nitrogen and Sulfur Under Sulfate Deficient Nutrition

Sulfur (S) deficiency effects on nitrogen (N) and S fluxes during vegetative growth of Brassica napus was investigated by tracing ¹⁵N and ³⁴S for 9 d of S-sufficient [1.5 mM sulfate (SO₄^2-)] and S-deficient (0.05 mM SO₄^2-) condition. A significant decrease in leaf osmotic potential and chlorophyll content was apparent after 9 d of S-deficiency. Sulfur uptake during 9 d was remarkably decreased by 94.3% by S-deficiency, whereas no significant change occurred for N uptake. The N and S deriving from uptake were mainly allocated to the leaves in control plants, but the S flow into leaves was largely restricted under S-deficient condition. The remobilization of stored N and S were mainly issued only from leaves in control plants, while from leaves and petiole in S-deficient ones. The remobilization of N and S mainly issued from leaves flows into the roots both in control and S-deficient plants.     

Effects of Exogenous Salicylic Acid on Physiological Characteristics of Peanut Seedlings under Iron-Deficiency Stress

The effects of salicylic acid (SA) on iron (Fe) deficiency in peanut (Arachis hypogaea L.) were studied by adopting the hydroponic experiment. Iron deficiency caused serious chlorosis, inhibited plant growth and dramatically decreased the concentration of Fe in the roots. Furthermore, it decreased the active Fe content and chlorophyll content, and disturbed ionic homeostasis. In addition, Fe deficiency significantly increased the content of malondialdehyde (MDA) and the superoxide anion (O₂^??) generation rate. Addition of SA increased Fe concentration in the shoots and roots, active Fe content, chlorophyll content, the net photosynthetic rate, and transpiration rate. Moreover, SA supplementation alleviated the excess absorption of manganese (Mn), copper (Cu) and zinc (Zn) induced by Fe deficiency. In addition, the chlorosis symptom was alleviated and the plant growth was improved. Meanwhile, addition of SA increased the activities of catalase (CAT) and peroxidase (POD), and decreased the content of MDA and the O₂^?? generation rate. These results suggest that exogenous SA can alleviate Fe-deficiency induced chlorosis by promoting the plant growth, improving the efficiency of Fe uptake, translocation and utilization, protecting antioxidant enzymes system, and stimulating mineral element maintenance.