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1.
Zucchini squash (Cucurbita pepo L.) plants were grown in a closed‐loop hydroponic system and supplied with nutrient solution (NS) containing NaCl at different concentrations (0.7, 3, 5, and 7 mM). The primary aim of the study was to define the relationship between the concentration of Na+ and Cl− in the root zone solution and the respective Na+/water or Cl−/water uptake ratios (uptake concentrations, UC). A second objective was to determine the UC of macronutrients (i.e ., N, P, K, Ca, and Mg) and to test whether they are influenced by the gradual increase of the root zone salinity due to progressive NaCl accumulation. Two experiments were conducted, of which one (spring crop) was used to parameterize an existing empirical model, while the second one (autumn‐winter crop) was commissioned to test the validity of the determined model parameters. Both Cl− and Na+ ions accumulated progressively in the root zone solution over time, showing a tendency to stabilize at final concentrations according to the corresponding NaCl treatment. The relationship between the Na+ and Cl− concentrations in the root zone and the Na+/water or Cl−/water uptake ratios was exponential and the model parameters successfully fitted to data from crops cultivated in different growth seasons. This model may be used to monitor Na+ and Cl− concentrations in the root environment of zucchini crops as relationships of the plant water consumption. The exposure of plants to NaCl affected the UC of N, K, Ca, and Mg, but the results for some nutrients were not consistent in both growth seasons. The measurements of plant growth characteristics (i.e ., biomass, yield, fruit quality, and photosynthesis) revealed that water resources containing up to 3 mM NaCl do not cause unacceptable yield losses in zucchini crops grown in completely closed hydroponic systems.  相似文献   

2.
A short-term experiment was conducted to investigate whether the effect of rootstock on plant response to salinity depends on the solanaceous species used as scion. Tomato cv. ‘Ikram’ and eggplant cv. ‘Black Bell’ were grafted onto two tomato interspecific hybrids (‘Beaufort’ and ‘He-Man’). Plants were grown in an open soilless cultivation system and supplied with two nutrient solutions: non-saline control and a saline solution (adding 15 mM Na2SO4, 3.7 dS m?1). Plant dry biomass production and partitioning were influenced by salinity, but its effect was depending on the rootstock/scion combination. ‘Beaufort’ eliminated the deleterious effect of salinity when tomato was used as scion, but reduced (?29.6%) the shoot biomass of eggplant. ‘He-Man’ had a different effect on scion growth under saline conditions: shoot biomass was less reduced in eggplant (?20.6%) than in tomato (?26.8%). Under salt stress, ‘Beaufort’ reduced the accumulation of Na+ in tomato leaves more than in eggplant, whereas no differences were observed between tomato and eggplant grafted onto ‘He-Man’. Stem Na+ accumulation followed a different pattern. The increase of Na+ in the stems was similar for tomato and eggplant grafted onto ‘Beaufort’, whereas stems of tomato accumulated more Na+ compared to eggplant grafted onto ‘He-Man’. The opposite response of the tested rootstocks to salt stress when the scion was either tomato or eggplant seems to be partially related to the capacity of the rootstock and scion to exclude Na+ from the shoot. However, the results of nutrient accumulation within plant tissues imply that other mechanisms in addition to ion competition are involved in the salt resistance of grafted plants.  相似文献   

3.
The aim of the present study was to determine uptake ratios between macronutrients and water for melon (Cucumis melo L. cv. Dikti) grown in a closed soilless cropping system. The obtained data can be used to establish standard nutrient solution compositions for melon crops grown in closed hydroponic systems under Mediterranean climatic conditions. Nutrient and water uptake by plants in the closed hydroponic system was compensated for by supplying replenishment nutrient solutions (RNS) differing either in the concentrations of K+, Ca2+, and Mg2+ or in their mutual ratio. The RNS, used as control treatment, had an electrical conductivity (EC) of 1.74 dS m?1 and contained 6.5 mM K+, 2.8 mM Ca2+, and 1.0 mM Mg2+ (K+ : Ca2+ : Mg2+ = 0.63 : 0.27 : 0.10). Control RNS was compared with two other RNS, both with a high Ca2+ level (4.2 mM). The K+ and Mg2+ levels in these two RNSs were: (1) not altered (corresponding to a ratio of K+ : Ca2+ : Mg2+ = 0.55 : 0.36 : 0.09; EC = 2.0 dS m?1) or (2) increased to maintain the same K+ : Ca2+ : Mg2+ ratio as in the control RNS (EC = 2.45 dS m?1). Nutrient to water uptake ratios, commonly termed uptake concentrations (UCs), were assessed by two alternative methods, i.e., (1) estimating the ratio between nutrient and water removal from the system or (2) estimating the ratio between the mass of the nutrient that was recovered from plant biomass and the water consumption. Over the two methods, mean UCs for N, P, K, Ca and Mg were 15.4, 1.31, 5.47, 3.78, and 1.02 mmol L?1, respectively, and tissue analysis resulted in a K : Ca : Mg molar ratio of = 0.55 : 0.34 : 0.11 in the whole plant. Moreover, the UCs tended to decrease as the crop aged although, in absolute values, the mass of nutrients absorbed increased following dry‐weight accumulation. Based on the obtained results, adapting the composition of the nutrient solution at least three times during the cropping period of melon is recommended. Further, the results revealed that the damage caused by the increase of the EC when attempting to maintain a target K+ : Ca2+ : Mg2+ ratio in the replenishment NS is higher than the benefits from the optimal cation ratio. Increasing K+ and Mg2+ concentration in addition to that of Ca2+ to maintain a standard K+ : Ca2+ : Mg2+ ratio raises the EC in the root zone (4.62 dS m?1), due to increased accumulation of nutrients, thereby reducing the mean fruit weight and concomitantly the total fruit yield (20% decrease). Leaf gas exchange, chlorophyll parameters and fruit taste quality were not influenced by the differences in macronutrient cation concentrations or ratios in the RNS, whereas phenolics and antioxidant capacity in melon fruit were enhanced by the increased root‐zone EC.  相似文献   

4.
An experiment developed in soilless culture was used to study the effect of several levels of Co2+ (0, 5, 15, and 30 mg L‐1 ) on the growth of tomato plants (Lycopersicon esculentum M. cv. Ramy). Absorption, transport, and accumulation of this metal in roots, stems, leaves, and fruits were also studied. Uptake was increased by application of this metal concentration in the nutrient solution, efficiency of root uptake of cobalt decreased with increased Co2+ treatment in the soilless culture system. The translocation of Co2+ from roots to aerial vegetative parts was increased with the time of experiment and Co2+ concentration in the nutrient solution. The presence of this metal in nutrient solution reduced tomato leaf production and elongation, specially at higher treatments.  相似文献   

5.
This trial was carried out to study the evolution of the nutrient parameters of the nutrient solution applied to tomato plants (Lycopersicum sculentum Mill. Forteza) cultivated in Mediterranean greenhouse conditions under different fertigation management models. The dynamic model is based on soil water content, which was measured by tensiometers, and on soil solutions obtained with suction cups (porous ceramic cup water samplers). The local traditional method consists of following technical recommendations, and the classical model requires the estimation of Crop Factor (Kc) and knowing the nutrient extraction. Nutrient solution and water applied are functions of the fertigation management criteria. The water used for fertigation was classified as C4-S3 according to the Riverside classification system. The cultivation period lasted from 15 August to 20 April. The nutrient parameters studied in nutrient and soil solution were pH, electrical conductivity (EC), nitrate (NO3 ?), phosphate (H2PO4 ?), potassium (K+), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), and chloride (Cl?). The pH shows similar trends under the different treatments. Electrical conductivity is in the range of 2.8–4.5 dS m?1. Chloride, sodium, magnesium, and sulfate are exclusively modified by the salt concentration in the irrigation water, so it can be assumed that the three treatments vary equally. Nitrate, potassium, phosphate, and calcium are modified depending on each fertigation management method. Soil solution is modified by the nutrient solution applied. Dynamic management allows low nutrient concentration in the nutrient solution to be maintained and keeps soil nutrient concentration low, reducing fertilizer losses and therefore aquifer contamination.  相似文献   

6.
The introduction of an active Na+ excretion system from salt-tolerant plants in salt-sensitive crop plants might necessitate enhancement of the robustness of K+ homeostasis and lead to improved plant growth under salt stress. To address this issue, we compared the acquisition and retention of K+ under excess Na+ concentrations in the common reed, which possesses excellent Na+ excretion ability, and low-Na+ excreting rice. Under excess Na+ concentrations, common reed maintained constant K+ content in all plant parts, whereas K+ content in rice decreased with increasing Na+ concentration. Preferential uptake of K+ against high Na+/K+ ratio in nutrient solution was approximately 10 times higher in common reed than in rice. The impact of excess Na+ on net K+ absorption rate of common reed was small. On the other hand, the net K+ absorption rate of rice was decreased by excess Na+ concentration. However, after the Na+ concentration in the nutrient solution was decreased from 50 to 1 mM, K+ absorption in rice recovered immediately. Thus, selectivity of K+ transporters or channels for K+ over Na+ in roots could be involved in the differences in K+ accumulation in rice and common reed.  相似文献   

7.
ABSTRACT

This experiment was conducted in a greenhouse in Vinces Los Rios (Ecuador). The aim of this work is to evaluate the relationship between different parameters and the nutrient demand of a greenhouse soilless cucumber production system in a tropical climate as well as to propose an empirical model for the design of the nutrient supply to the system. Considering the results obtained in this experiment, there was a high correlation between nutrient demands of the system with nutrient supplies and water uptake but not with leaf area index. With respect to the models, nutrient supplies and leaf area index were the most significant variables for nitrate (NO3?), chloride (Cl?) and manganese (Mn). For calcium (Ca2+), magnesium (Mg2+) and zinc (Zn), nutrients supply was the most significant variable and for the rest of nutrients [phosphates (H2PO4?), sulfates (SO42)?, potassium (K+), sodium (Na+) and iron (Fe)], the three variables assessed were significant.  相似文献   

8.
In tomato (Lycopersicon esculentum L. cv Trust Fl), effects of various nutrient treatments on growth, fruit yield and quality, nutrient uptake and accumulation were studied in a hydroponic system. Reductions of macronutrient concentrations to 50% (0.5 × C) or 25% (0.25 × C) of the control (C) levels as well as cessation of replenishment of the feed solution for the last 16 days after 7 months growth at control levels, had no adverse effect on growth, fruit yield and fruit quality. However, reduction of macronutrient concentration to 10% of control (0.1 × C) reduced fruit yield by ‐30%. Steady‐state influx and net flux of NO3 ‐ into the roots of 4–6 week‐old seedlings had not acclimated and showed concentration dependence from 1.1 mM (0.1 × C) to 11 mM (C). Whereas, Pi and K+ fluxes were similar at 0.5 × C and C levels, at 0.1 × C they were significantly lower than the fluxes at higher concentrations, showing lack of acclimation at this concentration. This lack of flux acclimation may account for the adverse effects of low concentration (0.1 × C) on yield. The results have been discussed in the context of eutrophication and it is suggested that in a non‐recirculating hydroponic system, NO3 ‐, Pi, and K+ levels can be reduced to 25% of the concentrations currently being used in commercial greenhouses (C). In a recirculating system, the crop may be grown at control levels and used to deplete the feed solution for ～3 weeks prior to release of the solution to the drain.  相似文献   

9.
ABSTRACT

Nutrient recycling in a space-based Bioregenerative Life Support System (BLSS) will require an understanding of nutrient dosage effects on crop production, plant tissue partitioning, and geochemical fates within crop systems. Sodium (Na+), fluoride (F?), and iodide (I?) are found in human waste streams. These elements were examined using crops in hydroponic systems. Lettuce, radish, spinach, and beet were used to study Na+ uptake and tolerance. Spinach, lettuce, and radish growth were inhibited at 8.0 × 10?2 M Na+ compared to the control. Beet growth improved at 2.0 and 4.0 × 10?2 M Na+ compared to the control. Rice plants were used to study F? and I? uptake and tolerance. Rice growth was inhibited at 5.0 × 10?4 M F? and at 5.0 × 10?6 M I?. Solution redox and sorption reactions were predicted with the aid of a chemical equilibrium model. A simulation model was used to predict element fates.  相似文献   

10.
The aim of this trial was to study the spatio-temporal variability in solution nutrient concentration under intensive greenhouse tomato production, to determine the number of suction-cups needed to obtain a representative sample and the influence by the position in the greenhouses. Twenty sampling points were selected within the greenhouse with one suction-cup per sampling point. One soil solution were sampled per point at weekly intervals to analyze for pH, electrical conductivity, chloride, nitrate, phosphate, sulfate, sodium, potassium, calcium, and magnesium (EC, Cl?, NO3?, H2PO4?, SO42—, Na+, K+, Ca2+, and Mg2+) concentrations. The pH, Cl?, H2PO4?, and SO42? concentrations showed no spatio-temporal variation but EC, NO3?, and K+ showed temporal variation. The spatial variability in EC, K+, Na+, Mg2+, and Ca2+ can be influenced by microclimate and topography. The numbers of suction cups required for a representative sample ranged from 1 to 10 depending on nutrient.  相似文献   

11.
Uptake and translocation of sodium in two cultivars of Lolium perenne The uptake and translocation of Na was investigated in two Lolium perenne cultivars (Dolewi and NFG). With increasing Na+ concentration in the nutrient solution (0, 1, 2 and 4 mMNa) the Na+ uptake per pot increased from 1.4 to 11.9 me/1 Na+ for Dolewi and from 1.1 to 6.9 me/l Na+ for NFG. The higher Na uptake by Dolewi can only partly be explained by better growth, the higher Na+ selectivity playing also an important role. In another experiment plants of both types were grown in solution cultures for 41/2 weeks at 15°C and 25°C, respectively. Hereafter the plants were supplied with 1.25 mM 24NaCl for six hours under equal conditions. Again the higher Na uptake and also a higher Na translocation (of about 20%) was found in Dolewi, whereas only 10% of the 24Na uptake had been translocated by NFG. When plants were grown in a nutrient solution with a lower temperature (at 15°C) the root lipids showed a higher linolenic acid and oleic acid content than the plants grown in a medium at 25°C. At the same time the 24Na uptake was higher in the plants grown at the lower temperature, yet the relationship between root lipids and Na uptake still remains to be elucidated.  相似文献   

12.
Eustoma grandiflorum (Raf.) Shinn. (lisianthus) is a moderately salt tolerant species that can be produced commercially under irrigation with saline wastewaters prevalent in two salt-affected areas of California. The objective of the present studies was to determine the effect of irrigation with saline waters of two different compositions on the ion accumulation and ion relations of lisianthus ‘Pure White’ and ‘Echo Blue’. The ionic composition of irrigation waters simulated the compositions typical of i) seawater dilutions (SWD) and ii) concentrations of Colorado River water (CCRW). Electrical conductivities (EC) of SWD and CCRW were between 2 and 12 dS · m?1. Plants irrigated with CCRW were higher in Ca2+ compared to plants irrigated with SWD water. Calcium was also higher in ‘Pure White’ than in ‘Echo Blue’. Increasing EC of irrigation water caused a significant decrease in shoot and leaf Ca2+ concentration in ‘Echo Blue’, but had no effect on Ca2+ content of ‘Pure White’ shoots and leaves. Magnesium concentration in ‘Echo Blue’ was higher than in ‘Pure White’. Electrical conductivity did not significantly affect Mg2+ concentration of either cultivar, despite the increasingly higher external concentration. Potassium concentration of young and mature leaves of ‘Echo Blue’ increased as EC increased from 2 to 8 dS · m?1, then decreased significantly once EC exceeded 8 dS · m?1. Potassium concentration of ‘Pure White’ leaves decreased over the range of salinity treatments tested, suggesting that the reduced potassium ion (K+) activity at EC levels of 8 dS · m?1, or less, that resulted in lower leaf?K+ in ‘Pure White’ did not cause a decrease in K+ uptake in ‘Echo Blue’. Increases in external Na+ caused a significant increase in Na+ in ‘Pure White’ leaves and these plants exhibited the best growth even when levels of Na+ were high enough to be considered detrimental for growth.  相似文献   

13.
Pistachio is one of the most important horticultural crops in Iran. The majority of the pistachio producing regions is located in arid and semi-arid areas with saline conditions. Therefore, selection of suitable rootstocks is important for increasing yield efficiency of this important nut crop. In this study, the effect of four water salinity levels (0.75, 5, 10 and 15 ds m?1) on growth indices and physiological parameters of four Pistacia vera L. rootstocks (Badami-e-Zarand A, Badami-e-Zarand B, Qazvini, and Sarakhs) were investigated under greenhouse conditions. After treatment for three months, leaf dry weight was reduced by about 30-50% at an irrigation water electrical conductivity (ECw) of 10 ds m?1. Badami-e-Zarand B was the most vigorous rootstock at the highest EC. Decreases in root and stem dry weight (average of all rootstocks combined) occurred at water salinity of 10 ds m?1. Chemical analysis of shoot and root indicated that the salinity affected the concentration and distribution of sodium (Na+), potassium (K+), and calcium (Ca2+) in pistachio rootstocks. The concentrations of Na+ and K+ increased with a rise in water salinity levels. Comparison between Na+ concentration of shoot and root showed that all examined rootstocks limited the Na+ transportation to shoot tissue up-to 15 ds m-1, and retained it in the roots. However, this ability was less in the Sarakhs rootstock. Based on measured parameters, Badami-e-Zarand B and Sarakhs could be considered as tolerant and sensitive pistachio rootstocks to water salinity, respectively.  相似文献   

14.
According to the biphasic model of growth response to salinity, growth is first reduced by a decrease in the soil osmotic potential (Ψo), i.e., growth reduction is an effect of salt outside rather than inside the plant, and genotypes differing in salt resistance respond identically in this first phase. However, if genotypes differ in Na+ uptake as it has been described for the two maize cultivars Pioneer 3906 and Across 8023, this should result in differences in Na+ concentrations in the rhizosphere soil solution and thus in the concentration of salt outside the plant. It was the aim of the present investigation to test this hypothesis and to investigate the effect of such potential differences in soil Ψo caused by Na+ exclusion on plant water relations. Sodium exclusion at the root surface of intact plants growing in soil was investigated by sampling soil solution from the rhizosphere of two maize cultivars (Across 8023, Pioneer 3906). Plants were grown in a model system, consisting of a root compartment separated from the bulk soil compartment by a nylon net (30 μm mesh size), which enabled independent measurements of the change of soil solution composition and soil water content with increasing distance from the root surface (nylon net). Across 8023 accumulated higher amounts of sodium in the shoot compared to the excluder (Pioneer 3906). The lower Na+ uptake in the excluder was partly compensated by higher K+ uptake. Pioneer 3906 not only excluded sodium from the shoot but also restricted sodium uptake more efficiently from roots relative to Across 8023. This was reflected by higher Na+ concentrations in the rhizosphere soil solution of the excluder 34 days after planting (DAP). The difference in Na+ concentration in rhizosphere soil solution between cultivars was neither due to differences in transpiration and thus in mass flow, nor due to differences in actual soil water content. As the lower Na+ uptake of the excluder (Pioneer 3906) was only partly compensated by increased uptake of K+, soil Ψo in the rhizosphere of the excluder was more negative compared to Across 8023. However, no significant negative effect of decreased soil Ψo on plant water relations (transpiration rate, leaf Ψo, leaf water potential, leaf area) could be detected. This may be explained by the fact that significant differences in soil Ψo between the two cultivars occurred only towards the end of the experiment (27 DAP, 34 DAP).  相似文献   

15.
Accumulation of excess sodium (Na+) in a soil causes numerous adverse phenomena, such as changes in exchangeable and soil solution ions and soil pH, destabilization of soil structure, deterioration of soil hydraulic properties, and increased susceptibility to crusting, runoff, erosion and aeration, and osmotic and specific ion effects on plants. In addition, serious imbalances in plant nutrition usually occur in sodic soils, which may range from deficiencies of several nutrients to high levels of Na+. The structural changes and nutrient constraints in such soils ultimately affect crop growth and yield. The principal factor that determines the extent of adverse effects of Na+ on soil properties is the accompanying electrolyte concentration in the soil solution, with low concentration promoting the deleterious effects of exchangeable Na+ even at exchangeable sodium percentage (ESP) levels less than 5. Consequent to an increase in the use of poor quality waters and soils for crop production, the problems of sodic soils can be expected to increase in future. The mechanisms that explain sodic behaviour can provide a framework in which slaking, swelling and dispersion of clay together with nutrient constraints in sodic soils may be assessed so that the practices to manage such soils can be refined for long‐term sustainable agriculture. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

16.
The influence of nutrient solution (1) mixing rate, and (2) time of use on pH and electrical conductivity (EC) of a recirculated nutrient solution used for the irrigation of a greenhouse soilless rose crop was studied. Measurements of microclimate variables, pH, and EC of nutrient solutions and crop transpiration were conducted. The measurements of pH and EC values of nutrient solutions mixed with different mixing rates and applied for crop fertigation were used to develop and calibrate a model for pH and EC prediction in relation to nutrient-solution mixing rate and time of use. Application of the calibrated model gave satisfactory results. It was found that nutrient solutions with high mixing rates or volume equal to or double that of the total water consumed by the canopy during the conservation period had the most stable EC evolution and minimal pH changes.  相似文献   

17.
不同浓度钠对甜菜生长及生理特性的影响   总被引：9，自引：2，他引：7  
采用1/2 Hoagland 营养液室内培养试验,研究不同浓度Na+ 对甜菜幼苗生理生化指标和营养元素吸收的影响。结果表明,0.759 mmol/L Na+可提高甜菜幼苗体内Na+ 含量和幼苗高度,增加叶面积（除了9 mmol/L Na+）和干物质量,降低叶片水势,提高叶片的相对含水量、 GPX和CAT的活性,促进甜菜幼苗叶片的吸水及保水能力。3 mmol/L Na+对甜菜幼苗的生长促进作用最明显,可提高CAT、 GPX活性并维持较高的SOD活性,降低MDA含量和相对电导率,未明显降低甜菜体内N、 P和K含量,是甜菜幼苗生长的最佳Na+浓度。  相似文献   

18.
About 7% of the total land around the globe is salt‐affected causing a great loss to agriculture. Salt stress refers to the excessive amount of soluble salts in the root zone which induce osmotic stress and ion toxicity in the growing plant. Among toxic ions, sodium (Na+) has the most adverse effects on plant growth by its detrimental influence on plant metabolism in inhibiting enzyme activities. An optimal potassium (K+) : Na+ ratio is vital to activate enzymatic reactions in the cytoplasm necessary for maintenance of plant growth and yield development. Although most soils have adequate amounts of K+, in many soils available K+ has become insufficient because of large amounts of K+ removal by high‐yielding crops. This problem is exacerbated under sodic or saline‐sodic soil conditions as a consequence of K+‐Na+ antagonism. Here K+ uptake by plants is severely affected by the presence of Na+ in the nutrient medium. Due to its similar physicochemical properties, Na+ competes with K+ in plant uptake specifically through high‐affinity potassium transporters (HKTs) and nonselective cation channels (NSCCs). Membrane depolarization caused by Na+ makes it difficult for K+ to be taken up by K+ inward‐rectifying channels (KIRs) and increases K+ leakage from the cell by activating potassium outward‐rectifying channels (KORs). Minimizing Na+ uptake and preventing K+ losses from the cell may help to maintain a K+ : Na+ ratio optimum for plant metabolism in the cytoplasm under salt‐stress conditions. It would seem a reasonable assumption therefore that an increase in the concentration of K+ in salt‐affected soils may support enhanced K+ uptake and reduce Na+ influx via HKTs and NCCSs. Although very useful information is available regarding K+‐Na+ homeostasis indicating their antagonistic effect in plants, current knowledge in applied research is still inadequate to recommend application of potassium fertilizers to alleviate Na+ stress in plants under sodic and saline‐sodic conditions. Nevertheless some encouraging results regarding alleviation of Na+ stress by potassium fertilization provide the motivation for conducting further studies to improve our understanding and perspectives for potassium fertilization in sodic and saline‐sodic environments.  相似文献   

19.
Sodic‐alkalinity may be more deleterious to plant growth than salinity. The objectives of this study were to determine whether 5‐aminolevulinic acid (ALA: an essential precursor for chlorophyll biosynthesis) foliar application could improve the sodic‐alkaline resistance of Swiss chard (Beta vulgaris L. subsp. cicla ) by regulating water uptake, ionic homeostasis, photosynthetic capacity, and antioxidant metabolism. Eight‐week‐old uniform plants were grown in nutrient medium without and with a sodic‐alkaline regime generated by a mixture of NaHCO3 and Na2CO3 (NaHCO3 : Na2CO3 = 9:1 molar ratio) for 12 d, and leaves were sprayed daily with water or ALA. The Na+ and ALA concentrations were gradually increased to 60 mM and 120 μM, respectively. ALA foliar application alleviated the physiological damage from sodic‐alkalinity, as reflected by the increases in plant dry weight, relative growth rate, chlorophyll, Mg2+ concentration, and the decrease in Na+ concentration. However, ALA foliar application did not change the water uptake capacity or the concentration of K+, Fe3+, and endogenous ALA in leaf tissues under sodic‐alkaline conditions. ALA foliar application effectively mitigated damage from sodic‐alkalinity because of the increased activity of antioxidant enzymes (catalase and guaiacol peroxidase), particularly superoxide dismutase activity, which was maintained at the same level as for control plants. These results suggest that ALA foliar application alleviated sodic‐alkaline stress mainly owing to its antioxidant capacity, and superoxide dismutase has the main responsibility for reducing oxidative stress in Swiss chard.  相似文献   

20.
Three cultivars of tomato (Lycopersicon esculentum Mill., cvs. Sera, 898, Rohaba) were grown under different levels of NaCl in nutrient solution to determine effects of salt stress on shoot and root dry matter (DM), plant height, water use efficiency (WUE, g DM kg‐1 water evapotranspired), shoot sodium (Na) and potassium (K) concentrations, and K versus Na selectivity (SK,Na). Increasing NaCl concentration in nutrient solution adversely affected shoot and root DM, plant height, WUE, K concentration, and K/Na ratio of all cultivars. Shoot Na concentrations increased with increasing NaCl concentration in the nutrient solution. Although increasing salt concentration in the solution adversely affected growth of all cultivars, the cultivar Sera had the highest shoot and root DM than the other two cultivars (898 and Rohaba). Shoot and root DM of cultivar 898 was most affected by salt, while cultivar Rohaba had an intermediate salt sensitivity. The cultivar Sera generally had higher WUE values, shoot K concentrations, and SK,Na, but had lower shoot Na concentrations than the other two cultivars when plants were grown under different salt levels. Greater Na exclusion, higher K uptake and shoot SK,Na are suggested as being plant strategies for salt tolerance.  相似文献   

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