Silicon and Potassium Nutrition Enhances Salt Adaptation Capability of Sunflower by Improving Plant Water Status and Membrane Stability

The relationships between salinity and mineral nutrition are extremely complex and may change depending on many factors in soil-plant system. We investigated the contribution of silicon (Si at 50 mg kg^?1 soil) and potassium (K at 40 and 60 mg K₂O kg^?1 soil) to improve salt tolerance in sunflower grown with 100 mM sodium chloride (NaCl). The experimental design was factorial based on a completely randomized design with five replications. Added NaCl increased sodium ion (Na⁺) accumulation by 966 percent in shoots and 1200 percent in roots but reduced shoot potassium ion (K⁺) concentration by 49 percent, root K⁺ 51 percent, and shoot K⁺/Na⁺ ratio 95 percent. However, Si and K application effectively reduced Na⁺ accumulation and increased K⁺ concentration and K⁺:Na⁺ ratio, with a significant improvement in plant growth and yield. Among all treatments, greater alleviative effects of Si and K were observed for 50 mg Si + 60 mg K₂O kg^?1 soil, which decreased shoot Na⁺ concentration by 67 percent, root Na⁺ 18 percent, and shoot Na⁺/root Na⁺ ratio 60 percent and increased shoot K⁺ by 198 percent, shoot K⁺/Na⁺ ratio 812 percent, membrane stability index (MSI) 35 percent, relative water content (RWC) 26 percent, and seed weight head^?1 86 percent compared to salt-stressed plants without supplemental Si and K. Most of the plant growth parameters were negatively correlated with Na⁺ accumulation but positively correlated with K⁺ and K⁺/Na⁺ ratio. This study suggests that Si and K mediated reduction in Na⁺ accumulation, and increase in K⁺ concentration, K⁺/Na⁺ ratio, RWC, and MSI are the main factors contributing to improved adaptation capability of sunflower to NaCl stress.     

Sodium exclusion is a reliable trait for the improvement of salinity tolerance in bread wheat

Identification of novel wheat (Triticum aestivum L.) germplasm is imperative to develop salt tolerant varieties. In the first phase, 400 accessions were screened against high salt stress (200 mM NaCl) on the basis of Na⁺ accumulation in leaf blade, and 40 genotypes with contrast reaction to salinity were selected. Salt tolerant group (25 genotypes) had higher leaf K⁺/Na⁺ ratio, maximum root and shoot lengths, leaf fresh/dry weights and chlorophyll content as compared to the salt sensitive group (15 genotypes). In second phase, physiologically based screening was performed on selected genotypes against varying salinity levels (0, 100 and 200 mM NaCl). GGE biplot analysis indicates that genotypes TURACO, V-03094, V0005, V-04178, Kharchia 65 and V-05121 were the most salt-tolerant and declared winners as depicted by more gaseous exchange relations and growth potential which was strongly correlated with proper Na⁺, K⁺ discrimination in leaf and root tissues. Genotypes PBW343*2, NING MAI 50, PGO, PFAU, V-04181, PUNJAB 85, KIRITATI, TAM200/TUI and TAM200 were poor performer due to more Na⁺ accumulation in leaf ultimately retarded growth. In conclusion, low Na⁺ accumulation in leaf can be used as the best screening criteria, employing a large set of genotypes in a breeding program.     

Differences in Physiological Traits Among Salt‐Stressed Barley Genotypes

Abstract

The effect of salinity on some physiological parameters in 16 barley genotypes with different salt tolerance was investigated. The results showed 50 mM NaCl treatment increased Na⁺/K⁺ ratio, malondialdehyde (MDA) and proline contents, and decreased cell membrane stability index (CMSI) and fresh shoot biomass (FSB) of all tested genotypes. Salt stress also resulted in a decreased chlorophyll (Chl) content and net photosynthesis (Pn) for most genotypes. Under higher salt stress (300 mM NaCl), the marked increase for Na⁺/K⁺, MDA, and proline content, and decrease for other parameters were found for all genotypes. The affected extent of these parameters by salt stress varied with genotypes. Proline accumulation in barley was associated with injured extent under salt stress, indicating it is not a defensive reaction to the stress. K⁺ uptake was less affected, whereas Na⁺ accumulation in plants was enhanced under high salt stress. The correlation analysis showed that MDA and proline content, Na⁺ concentration and Na⁺/K⁺ were negatively correlated with FSB, whereas other parameters examined in the study were positively correlated with FSB.     

Evaluation of Salt Tolerance and Its Relationship with Carbon Isotope Discrimination and Physiological Parameters of Barley Genotypes

Soil management through the cultivation of salt-tolerant plants is a practical approach to combat soil salinization. In this study, salt tolerance of 35 barley (Hordeum vulgare L.) genotypes was tested at four salinity levels (0, 100, 200, and 300 mM NaCl in Hoagland nutrient solution) at two growth stages (germination and vegetative). The relationship between salinity tolerance and carbon isotope discrimination (CID) was also accessed. Results of the study carried out under laboratory conditions showed that a negative linear relationship was observed between salt concentration and germination as well as other growth parameters. Some genotypes showed good salt tolerance at germination but failed to survive at seedling stage. However, five genotypes, namely, Jau-83, Pk-30109, Pk-30118, 57/2D, and Akermanns Bavaria showed better tolerance to salinity (200 mM) both at germination and at vegetative growth stage. The salt tolerance of these barley genotypes was significantly correlated with minimum decrease in K⁺:Na⁺ ratio in plant tissue with increase in the root zone salinity. However, the case was reversed in sensitive genotypes. CID was decreased linearly with increase in root zone salinity. However, salt-tolerant genotypes maintained their turgor by osmotic adjustment and by minimum increase in diffusive resistance and showed minimum reduction in CID (Δ) with gradual increase in rooting medium salt concentration. Results suggested that the tolerant genotypes make osmotic adjustments by selective uptake of K⁺ and by maintaining a higher K⁺:Na⁺ ratio in leaves. Moreover, CID technique can also be good criteria for screening of salt-tolerant germplasm.     

Growth and acquisition of Na,K and Ca in some elite sweetpotato [Ipomoea batatas (Lam.) L.] genotypes under salinity stress

Soil salinity is a concern in the wake of climate change challenges due to rising sea levels and coastal salinity in Papua New Guinea. A greenhouse experiment was conducted in Split Plot design, with five elite sweet potato genotypes (main-plot factors) and three levels of sodium chlroide (NaCl) concentrations (sub-plot factors) replicated six times. The vine cuttings of genotype RAB 45 showed very low mortality percentage (33%) at 600 mM NaCl concentration. At salinity level of 200 mM NaCl, aerial dry biomass of the genotypes was inversely but significantly (r = –0.40; p < 0.05) related to the accumulation of sodium (Na⁺) in the tissues. The Na⁺ accumulation in the tissues was antagonistic to the potassium (K⁺) and calcium (Ca²⁺) ions. Among the sweetpotato genotypes, Na⁺/K⁺ ratio decreased in the following order: RAB 45> KAV 11 > Northern Star > DOY 2 > L 46, which was more or less corroborated with the trend in the aerial dry matter.     

The regulation of accumulation and secretion of several major inorganic cations by Chinese Iris under NaCl stress

Chinese Iris (Iris lactea Pall. var. chinensis (Fisch.) Koidz.) is a monocotyledonous halophyte, which is considered an important salt-tolerant species. In this study, the plant growth, ion absorption and transportation and leaf secretion characteristics of Iris under sodium chloride (NaCl) stress were investigated using nutrient solutions with four NaCl concentrations ranging from 0 to 300 mmol L^?1. The main results indicated that Na⁺ secretion accounted for 5.7–11.5% of the ion distribution pattern of 90% of the ions accumulated in vivo by Iris. The ion transportation ratio was potassium > magnesium > calcium > sodium, (K⁺ > Mg²⁺ > Ca²⁺ > Na⁺), K⁺/Na⁺, Ca²⁺/Na⁺, Mg²⁺/Na⁺ in the shoot were greater than those in the root. K–Na and Ca–Na selectivity ratios showed an increasing trend overall. The contribution of salt secretion to the salt tolerance of Iris was tiny, which will be discussed in further research, achieving ion balance in vivo through selective absorption and transportation under salt stress is undoubtedly a primary salt-tolerance adaptation mechanism of Iris.     

Effect of different salts of sodium and potassium on the growth of Atriplex prostrata (Chenopodiaceae)

Although there are a variety of ions occurring in the soil throughout most of North America, the majority of halophyte literature focuses on the effects of NaCl on plants. In this study, a comparison is made of the effects of NaCl, KC1, Na₂SO₄, and K₂SO₄, on growth of the halophyte Atriplex prostrata Boucher ex DC (SYN: A. triangularis Willd.) at 0, ‐0.75, ‐1.00, and ‐1.50 MPa. Plant survival, height, number of leaves, nodes, and branches were recorded weekly. Photosynthesis was measured once before plants were harvested and dry mass was determined after one month. Content of Na⁺, K⁺,‐Mg²⁺, and Cl^‐ in plant tissue was also measured. A general trend observed was that all plant growth parameters decreased with a lowering of the medium osmotic potential, and that K⁺ salts were more inhibitory than Na⁺ salts. Ion content of plant tissue generally increased with a lowering of osmotic potential. Our data indicated that K⁺, a plant macronutrient, was more inhibitory to plant growth than Na⁺. It is possible that halophytes such as Atriplex prostrata could use Na⁺ as an osmoticum to adjust the vacuolar water potential, but were unable to use K⁺ for this function because of a specific ion toxicity. The inhibitory effect of salt on plant growth parameters and survival follow the pattern; K₂SO₄ >KCl>Na₂SO₄=NaCl.     

Effects of Potassium Sulfate on Adaptability of Sugarcane Cultivars to Salt Stress under Hydroponic Conditions

The effect of potassium sulfate (K₂SO₄) on adaptability of sugarcane to sodium chloride (NaCl) stress was investigated under hydroponic conditions. Two sugarcane cultivars, differing in salinity tolerance, were grown in half strength Johnson's solution at 80 mM NaCl with 0, 2.5 and 5.0 mM potassium (K) as K₂SO₄. Salinity disturbed above and below-ground dry matter production in both sugarcane cultivars. However, salt sensitive cultivar showed more reduction in shoot dry matter and higher root:shoot ratio compare to the salt tolerant cultivar under. Application of K significantly (p < 0.05) improved dry matter production in both sugarcane cultivars. The concentration of Na was markedly increased with increasing salinity; however, the application of K reduced its uptake, accumulation and distribution in plant tissues. Salinity induced reduction in K concentration, K-uptake, K utilization efficiency (KUE) and K:Na ratio in both sugarcane cultivars was significantly improved with the addition of K to the saline growth medium.     

Physiological Responses of Leymus Chinensis to Long-Term Salt,Alkali and Mixed Salt-Alkali Stresses

The aim of this study was to evaluate the physiological responses of Leymus chinensis (Trin.) Tzvel exposed to long-term salt, salt-alkali, and alkali stress in order to elucidate how L. chinensis can survive under alkaline-sodic soils. L. chinensis (30 days after germination) were stressed with salt [SS; sodium chloride (NaCl)], mixed salt-alkali [MS; molar ratio of NaCl: sodium carbonate (Na₂CO₃) = 2:1] and alkali salt (AS; Na₂CO₃) at four different levels of sodium (Na⁺) concentration (0, 75, 150, and 300 mM) for 60 days. L. chinensis showed 100% survival rate at all treatments except 300 mM SS (33.3%) and AS (18.9%). The growth and physiological parameters of survival plants were measured. As anticipated, growth of L. chinensis was inhibited after stresses, which reflected in the decline of plant height, dry weight and tiller number following the increased Na⁺ concentration. The content of Na⁺, proline, and soluble sugar in L. chinensis increased with the increasing Na⁺ concentration, suggesting that L. chinensis need to accumulate inorganic and organic solutes for resisting osmotic stress induced by various salt stresses. These processes ensure the water balance that can provide a relative normal physiological environment for L. chinensis. Potassium (K⁺) content of L. chinensis kept at a relative lower level than control to ensure the normal physiological processes. Chlorophyll content of stressed plant increased slightly compared to control plants, which can produce more energy for L. chinensis resisting various stresses. The increased malondialdehyde (MDA) content of stressed plants showed the damage of various stresses. Among the three treatments (SS, MS, and AS), the injury extent for L. chinensis can be expressed by AS>SS>MS, and MS was the most complicated for the counterbalance effects of soil electrical conduction and pH.     

Effect of Exogenous Silicon on Ion Distribution of Tomato Plants Under Salt Stress

Seedlings of two tomato cultivars were exposed to 0, 50, or 100 mM sodium chlroide (NaCl) stress with or without silicon (Si) for 10 days, and leaf electrolyte leakage, root activity, plant growth, and ion sodium, potassium, calcium, and magnesium (Na⁺, K⁺, Ca²⁺, and Mg²⁺) contents were determined. No significant differences were observed in total biomass and the root/crown ratio of salt-stressed plants treated with exogenous Si, but leaf electrolyte leakage of both cultivars treated with 50 mM NaCl and Si was lower than that in the same salt treatment without Si. Root activities of both cultivars were significantly affected by treatment with NaCl and exogenous Si. Application of Si induced a significant decrease in Na⁺ content and increases in K⁺, Ca²⁺, and Mg²⁺ contents in leaves of plants treated with 50 mM NaCl, and consequently the K⁺/Na⁺ and Ca²⁺/Na⁺ ratios increased by at least two times. The effects of Si on the ion contents of the roots were not notable.     

Silicon-induced changes in growth,ionic composition,water relations,chlorophyll contents and membrane permeability in two salt-stressed wheat genotypes

We investigated the effect of exogenously applied silicon (Si) on the growth and physiological attributes of wheat grown under sodium chloride salinity stress in two independent experiments. In the first experiment, two wheat genotypes SARC-3 (salt tolerant) and Auqab 2000 (salt sensitive) were grown in nutrient solution containing 0 and 100 mM sodium chloride supplemented with 2 mM Si or not. Salinity stress substantially reduced shoot and root dry matter in both genotypes; nonetheless, reduction in shoot dry weight was (2.6-fold) lower in SARC-3 than in Auqab 2000 (5-fold). Application of Si increased shoot and root dry weight and plant water contents in both normal and saline conditions. Shoot Na⁺ and Na⁺:K⁺ ratio also decreased with Si application under stress conditions. In the second experiment, both genotypes were grown in normal nutrient solution with and without 2 mM Si. After 12 days, seedlings were transferred to 1-l plastic pots and 150 mM sodium chloride salinity stress was imposed for 10 days to all pots. Shoot growth, chlorophyll content and membrane permeability were improved by Si application. Improved growth of salt-stressed wheat by Si application was mainly attributed to improved plant water contents in shoots, chlorophyll content, decreased Na⁺ and increased K⁺ concentrations in shoots as well as maintained membrane permeability.     

Use of Potassium Fertilization to Ameliorate the Adverse Effects of Saline-sodic Stress Condition (ECw: SARw Levels) in Rice (Oryza Sativa L.)

ABSTRACT

Salt-affected soils expand around the world and become a critical handicap for high crop yield. Saline-sodic soil contributed a major portion in salt-affected soils. Such types of soils have a sizable amount of Na⁺ in nutrient medium and that reduce the K⁺ uptake in plants. A hydroponic experiment was performed to investigate the ameliorative effect of different doses of potassium fertilizer (K₁ = 0.3, K₂ = 0.6 and K₃ = 1.2 mM L^?1) on rice (Oryza sativa L.) under different EC_w (6 dS m^?1) and SAR_w [12 and 24 (mmol L^?1)^1/2] levels. Application of K⁺ at elevated levels under saline-sodic conditions improved the concentration of anti-oxidant enzymes, plant physiological, and biochemical attributes by improving the K⁺: Na⁺ ratio in plant tissues. Total phenolic content, total soluble protein, and soluble sugar content of rice plant were increased with an increase in potassium dose and saline-sodicity. Maximum K⁺: Na⁺ ratios, 4.13 and 2.0 were observed in shoot and root, respectively upon application of K⁺ at 1.2 mM L^?1 in a solution having EC_w: SAR_w level of 6: 12. This study suggested that application of potassium at elevated levels (1.2 mM L^?1) has enhanced the rice growth by reducing the harmful effect of Na⁺ salts on plant physiology, biochemical attributes, and anti-oxidant enzymes under specific saline-sodic conditions.     

Effects of NaCl and silicon on ion distribution in the roots,shoots and leaves of two alfalfa cultivars with different salt tolerance

Abstract

The effects of exogenous NaCl and silicon on ion distribution were investigated in two alfalfa (Medicago sativa. L.) cultivars: the high salt tolerant Zhongmu No. 1 and the low salt tolerant Defor. The cultivars were grown in a hydroponic system with a control (that had neither NaCl nor Si added), a Si treatment (1 mmol L^?1 Si), a NaCl treatment (120 mmol L^?1 NaCl), and a Si and NaCl treatment (120 mmol L^?1 NaCl + 1 mmol L^?1 Si). After 15 days of the NaCl and Si treatments, four plants of the cultivars were removed and divided into root, shoot and leaf parts for Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe³⁺, Mn²⁺, Cu²⁺ and Zn²⁺ content measurements. Compared with the NaCl treatment, the added Si significantly decreased Na⁺ content in the roots, but notably increased K⁺ contents in the shoots and leaves of the high salt tolerant Zhongmu No.1 cultivar. Applying Si to both cultivars under NaCl stress did not significantly affect the Fe³⁺, Mg²⁺ and Zn²⁺ contents in the roots, shoots and leaves of Defor and the roots and shoots of Zhongmu No.1, but increased the Ca²⁺ content in the roots of Zhongmu No.1 and the Mn²⁺ contents in the shoots and leaves of both cultivars, while it decreased the Ca²⁺ and Cu²⁺ contents of the shoots and leaves of both cultivars under salt stress. Salt stress decreased the K⁺, Ca²⁺, Mg²⁺ and Cu²⁺ contents in plants, but significantly increased Zn²⁺ content in the roots, shoots and leaves and Mn²⁺ content in the shoots of both cultivars when Si was not applied. Thus, salt affects not only the macronutrient distribution but also the micronutrient distribution in alfalfa plants, while silicon could alter the distributions of Na⁺ and some trophic ions in the roots, shoots and leaves of plants to improve the salt tolerance.     

Individual and additive effects of Na+ and Cl− ions on rice under salinity stress

This study was attempted to assess the extent of toxicity contributed by Na⁺ and/or Cl^? ions individually, besides their possible additive effects under NaCl using physiological and biochemical parameters. Despite the fact that most annual plants accumulate both Na⁺ and Cl^? under saline conditions and each ion deserves equal considerations, most research has been focused on Na⁺ toxicity. Consequently, Cl^? toxicity mechanisms including its accumulation/exclusion in plants are poorly understood. To address these issues, effects of equimolar (100 mM) concentrations of Na⁺, Cl^? and NaCl (EC ≈ 10 dS m^?1) were studied on 15-day-old seedlings of two rice cultivars, Panvel-3 (tolerant) and Sahyadri-3 (sensitive), using in vitro cultures. All three treatments induced substantial reductions in germination rate and plant growth with greater impacts under NaCl than Na⁺ and Cl^? separately. Apparently, salt tolerance of Panvel-3 was due to its ability to exclude Na⁺ and Cl^? from its shoots and maintaining low (<1.0) Na⁺/K⁺ ratios. Panvel-3 exhibited better vigour and membrane stability indices coupled with lower reactive oxygen species and lipid peroxidation levels, besides stimulated synthesis of proline, glycine betaine and ascorbic acid. Overall, the magnitude of toxicity was observed in NaCl > Na⁺ > Cl^? manner. Though Cl^? was relatively less toxic than its countercation, its effect cannot be totally diminished.     

Evaluation of Salinity Effects on Ionic Balance and Compatible Solute Contents in Nine Grape (Vitis L.) Genotypes

The salinity tolerance of nine grape genotypes was studied. Salinity was applied as nutrient solutions containing 0, 25, 50, and 100 mM sodium chloride (NaCl) for two weeks. Growth was significantly reduced by salinity, whereas chloride (Cl^?) and sodium (Na⁺) contents increased. Sodium ion accumulation exceeded that of Cl^? in all treatments. Shirazi and H₆ had higher and lower Cl^? concentrations in their lamina than others. There were significant positive correlations (P < 0.01) between Cl^? and Na⁺ and negative correlation between Na⁺ and potassium (K⁺) in roots and laminas of all genotypes. Soluble sugars, proline, and glycine betaine contents increased in laminas of all of the genotypes with moderate salinity. There were positive correlations (P < 0.01) between lamina and root Na⁺ and Cl^? contents and compatible solutes in all genotypes. Overall results revealed that unlike Shirazi with higher Na⁺ and Cl^? accumulation in shoot, H₆ showed a higher capacity to restrict Na⁺ and Cl^? transport to shoot.     

Screening of tomato genotypes for salinity tolerance based on early growth attributes and leaf inorganic osmolytes

The experiment containing three replicates of completely randomized factorial treatments was conducted in a glasshouse under controlled conditions with three simulated soil salinity levels (control, 10 and 15 dS m^?1). Morpho-physiological traits (i.e. lengths, fresh weights and dry weights of root and shoot, number of leaves, root/shoot ratio, shoot Na⁺ accumulation, K⁺/Na⁺ ratio, Ca²⁺/Na⁺ ratio, membrane stability index, lycopene contents, chlorophyll-a and -b) were recorded to determine mechanism of salt tolerance of tomato at seedling stage. Principal component analysis (PCA) was used to express a three-way interaction of genotype × salinity level × traits that scattered the 25 tomato genotypes based on their morpho-physiological response to different NaCl levels. The negative association of Na⁺ with all other traits except root/shoot ratio and the morpho-physiological response trend of genotypes exposed that probable mechanism of salt tolerance was initially Na⁺ exclusion by abscising older leaves to have younger physiologically energetic, and lastly a higher activity of plants for root development to sustain them in saline soil. PCA three-way biplot efficiently recognized ANAHU, LA-2821, LO-2752, LO-2707, PB-017909, LO-2831-23 and 017860 as salt tolerant genotypes. On the other hand, ZARNITZA, GLACIER, LO-2692, LO-2576, BL-1079, 006233, 006232, 017856, NUTYT-701 and NAGINA were found to be salt susceptible.     

盐胁迫下柚实生苗生长、矿质营养及离子吸收特性研究

以坪山柚为材料,对盐胁迫下实生苗生长、矿质营养及离子吸收特性进行了研究。结果表明,沙培30d,80～200mmol/L盐胁迫,随盐浓度提高,坪山柚实生苗株高、叶面积、地上部干重和根部干重明显降低。溶液培养8d,坪山柚实生苗地上部及根Na+、Cl-含量随盐浓度的增加而增加,根及地上部K+、Ca2+、Mg2+以及P和Mn含量下降,Fe、Zn、Cu含量的变化因器官而异。其中,地上部Fe含量对盐胁迫敏感,可作为柚耐盐性鉴定指标。40mmol/L盐胁迫,坪山柚地上部K+/Na+、Ca2+/Na+、Mg2+/Na+值均显著下降,且Mg2+/Na+值+/Na+值>1;浓度≥160mmol/L盐胁迫,K+/Na+值+吸收、运转效率比Cl-高。     

Use of IR thermography in screening wheat (Triticum aestivum L.) cultivars for salt tolerance

Thermography is proposed to be an alternative non-destructive and rapid technique for the study and diagnosing of salt tolerance in plants. In a pot experiment, 30 cultivars of wheat (Triticum aestivum L.) were evaluated in terms of their leaf temperature and shoot growth and their ion distribution responses to NaCl salinity at two concentration levels: the control with electrical conductivity (EC) of 1 dS m^?1 and salinity treatment with EC of 16 dS m^?1 (150 mM). A completely randomized block design with factorial treatments was employed with three replications. The results indicated that thermography may accurately reflect the physiological status of salt-stressed wheat plants. The salt stress-based increase in leaf temperature of wheat cultivars grown at 150 mM NaCl reached 1.34°C compared to the control. According to the results obtained, it appears that thermography has the capability of discerning differences of salinity tolerance between the cultivars. Three salt-tolerant wheat cultivars, namely Roshan, Kharchia and Sholeh, had higher mean shoot dry matter (0.039 g plant^?1) and higher mean ratio of leaf K⁺/Na⁺ (14.06) and showed lower increase in the mean leaf temperature (0.37°C) by thermography compared to the control. This was while nine salt-sensitive cultivars, namely Kavir, Ghods, Atrak, Parsi, Bahar, Pishtaz, Falat, Gaspard and Tajan, had lower mean plant dry matter production (0.027 g plant^?1), lower mean ratio of K⁺/Na⁺ (9.49) and higher mean increases in leaf temperature (1.24°C).     

Evaluation of Extractants and Quantity–Intensity Relationship for Estimation of Available Potassium in Some Calcareous Soils of Western Iran

Accurate estimation of the available potassium (K⁺) supplied by calcareous soils in arid and semi‐arid regions is becoming more important. Exchangeable K⁺, determined by ammonium acetate (NH₄OAc), might not be the best predictor of the soil K⁺ available to crops in soils containing micaceous minerals. The effectiveness of different extraction methods for the prediction of K‐supplying capacities and quantity–intensity relationships was studied in 10 calcareous soils in western Iran. Total K⁺ uptake by wheat grown in the greenhouse was used to measure plant‐available soil K⁺. The following methods extracted increasingly higher average amounts of soil K⁺: 0.025 M H₂SO₄ (45 mg K⁺ kg^?1), 1 M NaCl (92 mg K⁺ kg^?1), 0.01 M CaCl₂ (104 mg K⁺ kg^?1), 0.1 M BaCl₂ (126 mg K⁺ kg^?1), and 1 M NH₄OAc (312 mg K⁺ kg^?1). Potassium extracted by 0.01 M CaCl₂, 1 M NaCl, 0.1 M BaCl₂, and 0.025 M H₂SO₄ showed higher correlation with K⁺ uptake by the crop (P < 0.01) than did NH₄OAc (P < 0.05), which is used to extract K⁺ in the soils of the studied area. There were significant correlations among exchangeable K⁺ adsorbed on the planar surfaces of soils (labile K⁺) and K⁺ plant uptake and K⁺ extracted by all extractants. It would appear that both 0.01 M CaCl₂ and 1 M NaCl extractants and labile K⁺ may provide the most useful prediction of K⁺ uptake by plants in these calcareous soils containing micaceous minerals.     

Effect of grafting on the growth and ion concentrations of cucumber seedlings under NaCl stress

Abstract

To assess whether grafting raised the salt tolerance of cucumber seedlings by limiting transport of Na⁺ to the leaf and to test whether the salt tolerance of grafted plants was affected by the shoot genotype, two cucumber cultivars (“Jinchun No. 2”, a relatively salt-sensitive cultivar, and “Zaoduojia”, a relative salt-tolerant cultivar) were grafted onto rootstock pumpkin (Cucurbita moschata Duch. cv. “Chaojiquanwang”, a salt-tolerant cultivar). Ungrafted plants were used as controls. The effects of grafting on plant growth and ion concentrations were investigated under NaCl stress. Reductions in the shoot and root dry weights, leaf area and stem diameter of grafted plants were lower and concentrations of K⁺ and Cl^? in the leaves were higher than those of ungrafted plants under the same NaCl stress. The Na⁺ concentration and Na⁺/K⁺ ratio in scion leaves and in the stems of grafted plants were lower, whereas those in rootstock stems and roots were higher than in ungrafted plants under the same NaCl stress. Shoot and root dry weight, leaf area and stem diameter were negatively correlated with leaf Na⁺ concentrations and Na⁺/K⁺ ratio, but were positively correlated with leaf K⁺ concentrations. The Na⁺ concentrations and Na⁺/K⁺ ratio were lower, whereas the K⁺ concentrations in the leaves of grafted “Zaoduojia” plants were higher than those in grafted “Jinchun No. 2” plants under the same NaCl stress. The reductions in leaf area and stem diameter of grafted “Jinchun No. 2” plants were more severe than those of grafted “Zaoduojia” plants. These results indicate that: (1) the higher salt tolerance of grafted cucumber seedlings is associated with lower Na⁺ concentrations and Na⁺/K⁺ ratio and higher K⁺ concentrations in the leaves, (2) grafting improved the salt tolerance of cucumber seedlings by limiting the transport of Na⁺ to the leaves, (3) the salt tolerance of grafted cucumber seedlings is related to the shoot genotype.