Responses of physiological parameters,grain yield,and grain quality to foliar application of potassium nitrate in two contrasting winter wheat cultivars under salinity stress

An experiment was conducted to test whether foliar application of KNO₃ on wheat in the heading stage could reduce salinity‐induced injuries, produce high grain yield, and improve grain quality. Salt‐resistant DK961 and salt‐sensitive JN17 wheat cultivars under 0 or 100 mM–NaCl conditions were foliarly watered with distilled water or a 10 mM–KNO₃ solution. The four treatments included: T₁ (CK₁), 0 mM NaCl + distilled water; T₂, 0 mM NaCl + 10 mM KNO₃; T₃ (CK₂), 100 mM NaCl + distilled water; T₄, 100 mM NaCl + 10 mM KNO₃. The results indicate that there were no differences (p > 0.05) in plant growth, grain yield, and grain quality between T₂ and T₁ in both cultivars, but these response variables were significantly lower in T₃ than in T₁. K⁺ : Na⁺ ratio, chlorophyll content, photosynthetic capacity, grain yield, flour yield, water absorbance, ash content, dough‐development time and dough‐stability time were significantly higher in T₄ than in T₃, while protein concentration, wet‐gluten concentration, and antioxidant enzyme activities were lower. Although foliar application of KNO₃ on JN17 enhanced plant growth, grain yield, and grain quality, these parameters were still lower in T₄ than in T₁. Our findings suggest that cultivating the salt‐resistant wheat cultivar combined with foliar application of KNO₃ at heading stage may alleviate salinity injuries and produce higher grain yield and better grain quality under saline conditions.     

Supplementary Potassium Nitrate Improves Salt Tolerance in Bell Pepper Plants

Abstract

The effect of supplementary potassium nitrate (KNO₃) on growth and yield of bell pepper (Capsicum annum cv. 11B 14) plants grown in containers under high root‐zone salinity was investigated. Treatments were (1) control, soil only and (2) high salt treatment, as for control plus 3.5 g NaCl kg^?1 soil. Above treatments were combined with or without either 0.5 or 1 g supplementary KNO₃ kg^?1 soil. Plants grown at high NaCl had significantly less dry matter, fruit yield, and chlorophyll than those in the control treatment. Supplementing the high salt soil with 0.5 and 1 g KNO₃ kg^?1 increased plant dry matter, fruit yield, and chlorophyll concentrations as compared to high salt treatment. Membrane permeability increased significantly with high NaCl application, but less so when supplementary KNO₃ was applied. High NaCl resulted in plants with very leaky root systems as measured by high K efflux; rate of leakage was reduced by supplementary KNO₃. These data suggest that NaCl status affect root membrane integrity. Sodium (Na) concentration in plant tissues increased in leaves and roots in the elevated NaCl treatment as compared to control treatment. Concentrations of K and N in leaves were significantly lower in the high salt treatment than in the control. For the high salt treatment, supplementing the soil with KNO₃ at 1 g kg^?1 resulted in K and N levels similar to those of the control. These results support the view that supplementary KNO₃ can overcome the effects of high salinity on fruit yield and whole plant biomass in pepper plants.     

Drought and Salt Stress Mitigation by Seed Priming with KNO3 and Urea in Various Maize Hybrids: An Experimental Approach Based on Enhancing Antioxidant Responses

Priming offers an effective means for counteracting different stresses induced oxidative injury and raising seed performance in many crop species. The present study was carried out to investigate the ability of potassium nitrate (KNO₃) and urea to promote the tolerance of different maize hybrids to drought and salt stresses to identify some biochemical parameters associated with KNO₃ and urea induced resistance in maize seedlings. An experiment was conducted in a controlled environment of the laboratory at the college of agriculture, Shiraz University, Shiraz Iran, during 2010. The first factor was stress type and intensity at five levels; moderate drought, severe drought, moderate salt, severe salt, and control (without stress). Seed priming was the second factor; water as control, KNO₃, and urea, and maize hybrids, including Maxima, SC704, Zola, and 304 were the third factor. Results indicated that the highest chlorophyll a (Ch a), chlorophyll b (Ch b), total chlorophyll (Ch T) contents, and carotenoids (Car) were found in no stress treatments and the most proline, protein contents, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities in severe drought treatment. Also, results revealed that generally, drought and salinity stresses decreased the amount of Ch a and the lowest Ch a was recorded for severe salinity stress (4.29 mg g^?1). Stresses caused decrease in Ch b, but the effect of sever salinity level was higher than the others. Priming of KNO₃ had significantly higher proline content than water and urea priming. The SC704 and 304 hybrids showed higher proline content than the other ones. Finally, the maize seed KNO₃ and urea priming lead to high activities of antioxidant defensive enzymes and increase the tolerance level to abiotic stresses such as salt and drought.     

EFFECT OF POTASSIUM NITRATE ON BREAKING BUD DORMANCY IN STRAWBERRY (FRAGARIA ANANASSA DUCH.) PLANTS

Strawberry (Fragaria ananassa Duch.) plants cv. ‘Selva’ were grown in soilless culture under greenhouse conditions to investigate the effectiveness of potassium nitrate (KNO₃) alone or accompanied with chilling treatments on vegetative growth of plants. Treatments included: 1) control plants, which did not receive treatment with any material (C2, C3, and C4) and/or chilling (C1): [C]; 2) plants, treated only with 1.5% KNO₃ (A1) or accompanied with chilling (A2, A3, and A4): [A] and 3) plants treated with 3% KNO₃ (B1) or accompanied with chilling (B2, B3, and B4): [B]. These treatments were applied continuously for four weeks. In each week, chilling hours increased. The highest and lowest leaf area resulted from the A1 and A4 treatments, respectively. The highest and lowest chlorophyll content were obtained by the C3 and C1 treatments, respectively. The highest and lowest petiole lengths resulted from the B4 and A2 treatments, respectively. The highest and lowest pedicel lengths were obtained with the B1 and C3 plants, respectively. These results showed that KNO₃ influences the growth rate of strawberry plants.     

氮素对NaCl胁迫下甜高粱种子萌发及芽苗生长与生理的影响

为了研究NaCl胁迫下氮肥对甜高粱种子萌发及芽苗生长和生理特性的影响,探索提高甜高粱耐盐能力的措施,室内设置不同盐分浓度、不同氮源及浓度条件下甜高粱萌芽试验。结果表明:NaCl胁迫和不同氮源对甜高粱发芽和芽苗生长的影响各有不同。NaCl浓度对甜高粱种子萌发有显著影响,在甜高粱芽苗生长阶段,通过提高保护酶活性和渗透调节物质而增强耐盐伤害能力是有限的。100 mmol.L 1NaCl胁迫下,根系POD活性最低,而叶片MDA积累量、可溶性糖含量、POD活性最高,受盐害程度最大。没有盐胁迫情况下增加不同氮源及氮量对甜高粱根叶生理特性的影响差异显著,当氮浓度在20 mmol.L 1时,细胞受伤害程度最低,生长最好。不同形态氮源对甜高粱发芽和幼苗生长的影响差异明显,NH4Cl的促进效果优于KNO3。在100mmol.L 1的NaCl胁迫下,施加铵态氮或硝态氮源均可以增强甜高粱芽苗期的POD活性,减少MDA积累,从而缓解盐胁迫带来的伤害。研究表明采取适当的氮肥调控措施可以提高甜高粱的耐盐能力。     

RESPONSE OF SALT STRESSED STRAWBERRY PLANTS TO FOLIAR SALICYLIC ACID PRE-TREATMENTS

Salinity has deleterious effects on plant growth and development through membrane stability, photosynthetic activity, protein content, and ionic composition; however, salicylic acid (SA) could restore these properties in plants. The objective of this study was to determine the ameliorative effects of SA as foliar pre-treatments on membrane permeability, proline and protein contents, chlorophyll a, b and total chlorophyll and ionic composition of strawberry cv. ‘Camarosa’ under saline conditions. Membrane permeability and proline content significantly increased and protein and chlorophyll contents significantly decreased by 6 mS cm^?1 application without SA treatment compared with the control (2 mS cm^?1) treatment. Membrane permeability decreased from 6.9 in 0 mM SA treatment to 5.2 by application of 1.0 mM SA under saline conditions and same to the control (5.2). Compared with 0 mM SA treatment, the average increases of proline and protein contents were 66.7% in 0.25 mM SA treatment and 62.2% in 0.1 mM SA treatment in 6 mS cm^?1 level, respectively. Chlorophyll b and total chlorophyll significantly increased by 0.25 mM SA treatments under saline conditions. The lowest and the highest chlorophyll b and total chlorophyll were obtained from 0 mM SA treatment (19.6 and 44.5 mg L^?1) and 0.25 mM SA treatment (28.6 and 52.9 mg L^?1) in 6 mS cm^?1 salinity level. Ionic compositions of leaves were significantly affected by salinity and SA treatments. Nitrogen in 1.0 mM SA treatment and P contents of leaves in 0.1 mM SA treatment significantly increased but Na and Cl contents of leaves significantly decreased by SA treatments in 6 mS cm^?1 salinity level. The results of this study were clearly indicated that the SA application on strawberry plants could ameliorate the deleterious effect of salt stress on membrane permeability, proline, protein, and chlorophyll contents. Therefore, SA treatment could offer an economic and simple application to salinity stress.     

Nickel toxicity in two durum wheat cultivars differing in drought sensitivity

The effects of nickel (Ni) on growth, leaf water status, and mineral nutrient concentration were studied in two wheat (Triticum durum Desf.) cultivars with different sensitivity to water stress: ‘Adamello’ [drought sensitive (DS)] and ‘Ofanto’ [drought tolerant, (DT)]. The DT cultivar showed a higher Ni absorption capacity: ‘Ofanto’ seedlings grown in the presence of 35 μM Ni had a 3.5 times greater concentration of Ni in roots than did ‘Adamello’. Despite the greater Ni tissue content, the DT cultivar exhibited better growth and nutritional status when compared to the DS cultivar. In the DS cultivar the concentration of chlorophyll a and b was reduced by Ni treatment. Chlorophyll a concentration decreased in the DT cultivar, but to a lesser extent than in the DS cultivar; chlorophyll b was not altered by Ni level in the DT cultivar. Nickel caused a decrease in the water potential (ψ_w) and relative water content (RWC) in both cultivars, but these decreases were greater in the DS cultivar. The antioxidative defense enzymes, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase, showed increased activity in Ni‐treated DS seedlings; this increase in activity was not observed in the DT seedlings. These data suggest that different wheat genotypes may markedly differ in Ni uptake and sensitivity and that a enhanced capacity to counteract Ni stress may be associated with drought resistance.     

硅对盐胁迫下大麦叶片的亚显微结构、叶绿素含量及光合活力的影响

Two contrasting cultivars of barley(Hordeum vulgare L.):Kepin No.7(salt sensitive),and Jian 4(salt tolerant)were grown in a hydropon ics system with 2 NaCl levels:60 mmol NaCl L^-1 and 120 mmol NaCl L^-1 ,and 3 Si levels:0 mmol Si L^-1 ,0.5 mmol Si L^-1 and 1.0 mmol Si L^-1 (as silicic acid).Compared with the plants treated with 60 mmol NaCl L^-1 alone,the leaf chlorophyll contents of plants rreated with salt and Si increased significantly ofr salt-sensitive cultivar at tillering stage,but for alt-tolerant cultivar,the addition of Si resulted in an obivous increase in the leaf chlorophyll content of plants exposed to 120 mmol NaCl L^-1 ,However,this Si-enhancement of leaf chlorophyll content was also observed in the salttolerant plants at joninting stage,but not in the salt-sensitive plants.Moreover,leaf chlorophyll content was consistently higher for the salt-tolerant cultivar than for the salt-sensitive cultivar irrespective of salt and/or Si treatment .Compared with the plants treated with sal alont ,net CO2 assimilation rate in plant leaves increased significantly for both cultivars when treated with salt and Si, Teh addition of Si to the salt teatment was found to improve the cell ultrastructure of leaves.Under salt stress condition,the double membranes of chloroplasts disappeared,but membrane integrity was markedly improved in the salt treatment supplemented with Si.Silicon was also found to ameliorate the damage to the ultrasturcture of chloroplast granae which appeared to be disintegrated and vague in salt treatments without added Si.The results support previous work which showed that Si decreases the permeability of plasma membranes of salt-stressed barley,thus mitigating salt damage.     

Effect of Salt Stress on Growth and Chlorophyll Content of Some Cultivated Cotton Varieties Grown in Syria

Five upland cotton varieties (Gossypium hirsutum L.) (Aleppo 118, Aleppo 33/1, Aleppo 90, Raqqa 5, and Deir-Ezzor 22) were evaluated under different salinity indices [0, 50, 100, and 200 mM sodium chloride (NaCl)] for 56 days. During the course of the experiment, plant size (HT), leaf number (LN) and leaf area (LA), chlorophyll SPAD (Soil Plant Analyses Development), chlorophyll (Chl) a and b content, and osmotic potential were measured in both control and salt-stressed plants for all tested varieties. Salt-stress application reduced the HT and LN of all varieties, whereas LA decreased as salinity level increased for all tested varieties comapared to their respective control expect for Deir-Ezzor 22 variety. Our data showed that LA, Chl a and b, and chlorophyll SPAD can be used to discriminate between salt-tolerant varieties and salt-sensitive ones. In this respect, Deir-Ezzor 22 variety differed by showing high salt tolerance relative to Aleppo 118 and Aleppo 33/1 varieties. Therefore, this investigation aimed for a better understanding of the different responses presented among these varieties toward salt treatment.     

Effectiveness of potassium in mitigating the salt-induced oxidative stress in contrasting tomato genotypes

To check the efficacy of potassium in alleviating oxidative stress under salt stress, salt-tolerant (Indent-1) and salt-sensitive (Red Ball) tomato (Lycopersicon esculentum Mill.) genotypes were exposed to three levels of sodium chloride (NaCl) (0, 75, 150 mM) and two levels of potassium (4.5 and 9 mM) in solution and foliar form. Thirty days of treatments revealed that increasing NaCl stress increased lipid peroxidation (malondialdehyde, MDA) and correspondingly the activity of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; and glutathione reductase GR) in both genotypes. However, higher potassium (K) level in solution or foliar spray during the salt-induced stress decreased MDA and antioxidant activity and increased the growth in salt-tolerant genotype than in the salt-sensitive genotype. Decrease in MDA concentration, activity of antioxidant enzymes, and increase in the growth of tomato plants by the application of potassium under salt stress suggest that potassium is an effective ameliorating agent against salt-induced oxidative damage.     

Inducing Salt Tolerance in Wheat by Exogenously Applied Ascorbic Acid through Different Modes

ABSTRACT

In order to assess whether exogenous application of ascorbic acid (AsA) through different ways could alleviate the adverse effects of salt-induced adverse effects on two wheat cultivars differing in salinity tolerance, plants of a salt tolerant (‘S-24’) and a moderately salt sensitive (‘MH-97’) cultivar were grown at 0 or 120 mM sodium chloride (NaCl). Ascorbic acid (100 mg L^?1) was applied through the rooting medium, or as seed soaking or as foliar spray to non-stressed and salt stressed plants of wheat. Salt stress-induced reduction in growth was ameliorated by exogenous application of ascorbic acid through different ways. However, root applied AsA caused more growth enhancement under saline conditions. Leaf ascorbic acid, catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities were also maximal in salt stressed plants of both cultivars treated with AsA through the rooting medium. Furthermore, leaf ascorbic acid, CAT, POD, and SOD activities were higher in salt stressed plants of ‘S-24’ than those of ‘MH-97’. Root applied AsA caused more enhancements in photosynthetic rate. Root applied AsA caused more reduction in leaf sodium (Na⁺) compared with AsA applied as a seed soaking or foliar spray. Overall, AsA-induced growth improvement in these two wheat cultivars under saline conditions was cultivar specific and seemed to be associated with higher endogenous AsA, which triggered the antioxidant system and enhanced photosynthetic capacity.     

Effect of presowing seed treatments on germination and early seedling growth of wheat varieties under saline conditions

The effect of presowing wheat seed treatments was investigated for the salt-sensitive variety Blue Silver and relatively salt-tolerant variety PARI-73 at the germination and early seedling stages. Seeds were treated with distilled water (DW) or 10/50 mm KCl, KNO₃ , CaCl₂, Ca(NO₃)₂ and then germinated in DW or 200 mm NaCl. Treatment with calcium (Ca) or potassium (K) did not lead to a significantly higher rate for final germination than the DW treatment. Ca salt treatments significantly improved shoot growth during the early seedling establishment stage in both varieties, especially in the salt-sensitive variety Blue Silver. There were significant differences in the Ca content of seeds after various presowing treatments. There were also significant differences between both varieties in the ion contents after seed treatment. However, these differences appeared to be related to the improvement of shoot growth during the early seedling establishment stage and not to the effectiveness of pres owing seed treatments in increasing germination.     

氯化钠胁迫对不同耐盐黄瓜品种的损伤效应及反射光谱特性的影响

研究了氯化钠胁迫对不同耐盐黄瓜品种的损伤效应及反射光谱特性的影响。结果表明,黄瓜品种新泰密刺比津优1号具有更强的耐盐性;盐处理明显增加了黄瓜叶片在可见光区的光谱反射率,并且盐敏感品种津优1号在盐胁迫下光谱反射率增加的幅度明显高于耐盐品种新泰密刺,尤其在绿光区差异更为明显。利用光谱反射指标得出的叶绿素含量、叶黄素循环库的大小与黄瓜的盐害程度及不同品种的耐盐程度有密切关系,反射光谱特性可以用来作为筛选黄瓜耐盐的生理指标。     

Effects of foliar spray of two kinds of zinc oxide on the growth and ion concentration of sunflower cultivars under salt stress

This study investigated the effects of foliar application of normal and nano-sized zinc oxide on the response of sunflower cultivars to salinity. Treatments included five cultivars (‘Alstar’, ‘Olsion’, ‘Yourflor’, ‘Hysun36’ and ‘Hysun33’), two salinity levels [0 and 100 mM sodium chloride (NaCl)], and three levels of fertilizer application. Fertilizer treatments were the foliar application of normal and nano-sized zinc oxide (ZnO). Foliar application of ZnO in either forms increased leaf area, shoot dry weight, net carbon dioxide (CO₂) assimilation rate (A), sub-stomatal CO₂ concentration (Ci), chlorophyll content, Fv/Fm, and Zn content and decreased Na content in leaves. The extent of increase in chlorophyll content, Fv/Fm and shoot weight was greater as nano-sized ZnO was applied to the normal form. The results show that the nano-sized particles of ZnO compared to normal form has greater effect on biomass production of sunflower plants.     

Effects of biofertilizers and cycocel on some physiological and biochemical traits of wheat (Triticum aestivum L.) under salinity stress

In order to study the effects of biofertilizers and cycocel on some physiological and biochemical characteristics of wheat (Triticum aestivum L.) under salinity condition, a factorial experiment was conducted based on randomized complete block design with three replications under greenhouse condition in 2015. Treatments were included salinity in four levels [no salt (control or S₀), salinity 30 (S₁), 60 (S₂) and 90 (S₃) mM NaCl equivalent of 2.76, 5.53 and 8.3 dS m^?1, respectively], four biofertilizers levels [no biofertilizer (F₀), seed inoculation by Azotobacter chrocoocum strain 5 (F₁), Pseudomonas putida strain 186 (F₂), both inoculation Azotobacter + Pseudomonas (F₃)] and three cycocel levels [without cycocel as control (C₀), application of 600 (C₁) and 1000 (C₂) mg L^?1]. Results showed that salinity severe stress (90 mM) decreased chlorophyll content, relative water content (RWC), total chlorophyll, photochemical efficiency of PSII and yield of wheat. Whereas, soluble sugars and proline content, electrical conductivity (EC), the activity of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO) enzymes were increased. Similar results were observed in CAT, POD and PPO activities due to inoculation by biofertilizers and cycocel. Salinity at 30 mM increased the photochemical efficiency of PSII and chlorophyll content in plants grown under biofertilizer and cycocel treatment but with increasing salinity up to 90 mM mentioned parameters were decreased. The highest proline and soluble carbohydrate at all salinity levels were observed in plants treated in the highest cycocel level and Azotobacter+ Pseudomonas application. Generally, it was concluded that biofertilizers and cycocel can be used as a proper tool for increasing wheat yield under salinity condition.     

MYCORRHIZAL INFLUENCE ON FRUIT YIELD AND MINERAL CONTENT OF TOMATO GROWN UNDER SALT STRESS

Tomato (Lycopersicon esculentum Mill.) yields are known to decrease for plants grown in saline soils. This study was conducted to determine the effects of arbuscular mycorrhizal fungi (AMF) inoculation on fruit yield and mineral content of salt-tolerant and salt-sensitive tomato cultivars grown with varied levels of salt. NaCl and CaCl₂were added to soil in the irrigation water in equal molar ratios to give EC_e values of 1.4 (nonstressed) and 4.9 dS m^?1 (salt stressed). Plants were grown in a greenhouse using unsterilized, low phosphorus (P) (silty clay) soil-sand mix. Mycorrhizal root colonization occurred whether cultivars were salt stressed or nonstressed, but the extent of AMF root colonization was higher in AMF inoculated than uninoculated plants. The salt tolerant cultivar ‘Pello’ generally had higher AMF root colonization than the salt sensitive cultivar ‘Marriha’. Shoot dry matter (DM) yield, fruit fresh yield, and AMF colonization were higher for plants grown under nonstressed than for plants grown under salt stressed conditions. Shoot DM and fruit fresh yields were higher in AMF inoculated than uninoculated plants grown with or without salt stress. Pello generally had higher fruit fresh yield per plant and fruit weight than Marriha, but these differences were only significant for fruit weight in unioculated plants grown under salt stressed conditions. The enhancement in fruit fresh yield due to AMF inoculation was 26 and 23% under nonstressed and 28 and 46% under salt stressed treatments for Pello and Marriha, respectively. For both cultivars, fruit contents of P, potassium (K), zinc (Zn), copper (Cu), and iron (Fe) were higher in AMF inoculated compared with uninoculated plants grown under nonstressed and salt stressed conditions. Fruit Na concentrations were lower in AMF inoculated than uninoculated plants grown under salt stressed conditions. The enhancement in P, K, Zn, Cu, and Fe acquisition due to AMF inoculation was more pronounced in Marriha than in Pello cultivar under salt stressed conditions. The results of this study indicated that AMF inoculated plants had greater tolerance to salt stress than unioculated plants.     

Salt Tolerance of Canola in Relation to Accumulation and Xylem Transportation of Cations

ABSTRACT

This study was conducted in a greenhouse to evaluate the root and shoot response of canola (Brassica napus L.) to salt-stress conditions and the remobilization, deposition, and input rate of sodium (Na), potassium (K), and magnesium (Mg) at different salinity levels using two canola cultivars. A salt-tolerant (‘Kristina’) cultivar and a salt-sensitive (‘Hyola 308’) cultivar were grown in nutrient solutions with 0, 50, 100, 150, and 200 mol m^?3 NaCl for 7 d. The plants were harvested after 6, 12, 18, and 24 h and 3 and 7 d after salt treatment. The results indicated that increasing salinity significantly decreased shoot and root weights 7 d after treatment. Also, K content and K-Na selectivity decreased in both cultivars, but the changes in ‘Hyola 308’ were greater than in ‘Kristina.’ Electrolyte leakage was increased significantly by salinity, and cell-membrane stability of ‘Hyola 308’ was damaged more than that of ‘Kristina’. Sodium import, transport, and deposition was increased by salinity concentration but remobilization was decreased. The K and Mg import, deposition, and remobilization were also decreased. From this experiment we can conclude that greater K and Mg remobilization in ‘Kristina’ could be a mechanism of salt tolerance in canola.     

Nutritional (Fe-Mn) interactions in ‘Big Top’ peach plants as influenced by the rootstock and by the soil CaCO3 concentration

Manganese (Mn) toxicity in plants is often not a clearly identifiable disorder and it can interfere with the absorption, translocation, and utilization of other elements such as Ca, Mg, Fe, and P. Soil conditions, management factors, and the use of different genotypes of rootstock can determine the degree of Mn toxicity and of interaction with other elements in the orchard. Five plants of the cultivar ‘Big Top’® grafted onto itself, onto plum rootstock ‘Mr.S.2/5’ and onto hybrid peach x almond rootstock ‘GF677’ were grown in 25-L containers under three treatments, 0, 20, 30% concentration of total lime, obtained by mixing powdered CaCO₃ to a sandy soil. Plants were fertilized with manure and a solid fertilizer early in April and irrigated in summer periodically with water rich in manganese. After just 28 d, active lime caused a decrease of chlorophyll SPAD index especially in plants grafted on itself, while those grafted on the tolerant ‘GF677’ rootstock behaved better than those grafted on ‘Mr.S.2/5.’ From June to September, irrigation caused increases in soil Mn concentration and Mn concentration in control plants. This caused first a serious defoliation in Big Top / Big Top plants and then a re-greening of cultivar grafted onto ‘Mr.S.2/5’ and ‘GF677,’ probably due to the interaction between iron and manganese at high pH. In particular the 20% CaCO₃ addition to the soil preserved the plants of cultivar grafted onto ‘Mr.S.2/5’ from Mn toxicity, as shown by their high chlorophyll content and growth and lower Mn leaf concentrations. Plants grafted onto ‘GF677’ rootstock showed the best behaviour under 30% CaCO₃ treatment associated to higher Fe(III)-reducing capacity and photosynthetic activity. Rootstocks and soil conditions (lime and waterlogging) influenced mineral status and growth of the peach cultivar ‘Big Top,’ particularly by interacting together and modifying Fe-Mn availability.     

Ameliorative Effect of Calcium Nitrate on Cucumber and Melon Plants Drip Irrigated with Saline Water

Abstract

Cucumber (Cucumis sativus cv. Orlando) and melon (Cucumis melo cv. Ananas) were field grown to investigate the effects of supplementary calcium nitrate applied to irrigation water on plant growth and fruit yield of salt stressed and unstressed cucumber and melon plants. Treatments were (1) control: normal irrigation water (C); (2) normal irrigation water plus supplementary 5 mM Ca(NO₃)₂ added to the irrigation water (C + CaN); (3) salt treatment: C plus 60 mM NaCl added irrigation water (C + S); and (4) supplementary Ca(NO₃)₂: C + S plus supplementary 5 mM Ca(NO₃)₂ added to the irrigation water (C + S + CaN). Plants irrigated with water containing high NaCl produced less dry matter, fruit yield, and chlorophyll than the control treatments of both species. Supplementing irrigation water with Ca(NO₃)₂ resulted in increases in dry matter, fruit yield, and chlorophyll concentrations over plants irrigated with saline water. Membrane permeability increased with C + S treatment for both species. Supplementary Ca(NO₃)₂ restored membrane permeability. Sodium (Na) concentration in plant tissues increased in leaves and roots in the elevated NaCl treatment. Concentrations of Ca and N in leaves were decreased in the high salt treatment and fully restored by supplementary Ca(NO₃)₂. These results clearly show that supplementary Ca(NO₃)₂ can partly mitigate the adverse effects of saline water on both fruit yield and whole plant biomass in melon and cucumber plants.     

Foliar-applied trehalose modulates growth,mineral nutrition,photosynthetic ability,and oxidative defense system of rice (Oryza sativa L.) under saline stress

A tub experiment was conducted to assess the effect of exogenously applied trehalose (0, 10, and 20 mM) on various attributes of two rice cultivars (Bas-385 and Bas-2000) under salt stress (0, 50, 100, and 150 mM). Salinity decreased growth, gas exchange characteristics, shoot and root potassium (K⁺) ions, hydrogen peroxide (H₂O₂), total soluble proteins, activity of catalase (CAT), and yield attributes, while it increased chlorophyll contents, shoot and root sodium (Na⁺) and calcium (Ca²⁺), malondialdehyde (MDA), glycinebetain (GB), free proline, and peroxidase (POD) activity. Foliar-applied trehalose improved growth attributes, net photosynthetic rate, GB, total soluble proteins, superoxide dismutase (SOD) and yield. Yield was not obtained at 150 mM salt stress. The rice cultivar Bas-2000 showed better performance with respect to gas exchange attributes and activities of enzymatic antioxidants. Overall, varying levels of foliar-applied trehalose proved to be effective in ameliorating adverse effects of salt stress on rice.