Effect of Calcium and Potassium Nutrition on Yield,Ion Content,and Salt Tolerance of Brassica campestris (rapa)

When plants encounter salinity, growth is reduced initially by water stress and subsequently by toxic levels of ions and by interference with nutrient acquisition and translocation. Calcium (Ca^{2 +}) in particular seems to have an important role in salt tolerance and there are reports of a beneficial effect of increasing Ca^{2 +} availability. Higher potassium (K⁺) concentrations in plants may also improve salinity tolerance as sodium (Na)⁺/K⁺ ratios have been shown to be important. Previous work with a range of Acacia species has suggested that endogenous seed Ca^{2 +} and K⁺ concentrations might influence salinity tolerance at germination, but this has not previously been tested with a single species. The objectives of this investigation were thus to determine whether (1) altered Ca^{2 +} and K⁺ nutrition of Brassica campestris (rapa) L. plants affects the yield and ion content of their seeds, and (2) seeds with different Ca^{2 +} and K⁺ contents differ in their salinity tolerance. Plants were grown in a growth room or greenhouse in (1) Gem® horticultural sand (2) Silvaperl® perlite and sand (2:1), or (3) Shamrock® Medium General Purpose Irish Sphagnum Peat and Vermiperl® vermiculite (1:1). Plants in each growth substrate were supplied with nutrient solutions based on a modified Hoagland's solution as a control, low Ca^{2 +} and low K⁺ solutions containing those elements at half the control strength, but all other mineral elements as far as possible at control strength, and high Ca^{2 +} and high K⁺ solutions containing those elements at double control strength but all other mineral elements, as far as possible, at control strength. An increase in substrate available Ca^{2 +} and K⁺ resulted in increased Ca^{2 +} and K⁺ concentration in seeds, respectively, and was accompanied by a reduction in seed K⁺ and Ca^{2 +}, respectively. The Ca^{2 +} and K⁺ concentrations of seeds affected their salinity tolerance. Increases in seed Ca^{2 +}, K⁺ or Ca^{2 +}+ K⁺ concentrations decreased salinity tolerance at germination. The results, especially in terms of Ca^{2 +} nutrition, contradict previous results of an increased salinity tolerance with increased Ca^{2 +} and/or K⁺ concentrations.     

MODELING GROWTH AND ION CONCENTRATION OF LILIUM IN RESPONSE TO NITROGEN:POTASSIUM:CALCIUM MIXTURE SOLUTIONS

Nutrient solution composition plays an important role in root uptake rate due to interactions among nutrients and internal regulation. Studies to determine the optimum nutrient solution concentration are focused on individual ions, ignoring the adaptation mechanisms triggered by plants when growing in a varying external nutrient concentration. The objective of the present study was to determine the response in growth and tissue ion concentration of lilium cv. ‘Navona’ to nutrient mixtures of varying proportions of nitrogen (N), potassium (K⁺), and calcium (Ca²⁺) in solution using mixture experiments methodology in order to determine the optimum concentration. Bulbs of lilium were transplanted in plastic crates and drip-irrigated with the treatment solutions, which consisted of a mixture of N, K⁺, and Ca²⁺ whose total concentration was 340 mg L^?1 and minimum concentrations of each ion was 34 mg L^?1. Chlorophyll concentration (SPAD), shoot fresh weight (FW), leaf FW, and leaf area were measured 60 days after transplanting and ion analysis was performed on shoot tissues from selected treatments. Lilium exhibited a moderate demand for N and K⁺ (136–170 mg L^?1 N and 116–136 mg L^?1 K⁺) and a very low demand for Ca²⁺ (34–88 mg · L^?1). This low demand may be due to the remobilization of the nutrients stored in the bulbs. Integrating the predictions of the models estimated to produce >90% of maximum growth, the optimum nutrient solution should contain Ca²⁺ at a concentration between 34 and 126 mg · L^?1, K⁺ between 119 and 211 mg · L^?1, and N between 92 mg · L^?1 and 211 mg · L^?1. Increasing external N concentration affected internal N concentration but not internal K⁺ or Ca²⁺ concentrations, despite that the increase in external N was associated with a decrease in external K⁺ and Ca²⁺. Similar trends were observed for external K⁺ and Ca²⁺ concentration. In conclusion, lilium was able to maintain a relatively constant K⁺ and Ca²⁺ concentration regardless of the lower concentration in the nutrient solution when N was increased (similar response was observed for K⁺ and Ca²⁺) and it has a low Ca²⁺ demand and moderate N and K⁺ supply.     

环境因素对小麦根系非选择性阳离子通道(NSCCs)转运钾的影响

以石家庄8号小麦作为研究对象,通过添加钾载体抑制剂和钾专性通道抑制剂的方法,探讨了温度变化和重金属镉、铜对植物根系的非选择性阳离子通道(NSCCs)转运钾离子的影响。结果显示,NSCCs转运钾的最适温度在35℃左右,低温和高温都会使NSCCs的吸钾速率下降。较高的温度(40℃)对NSCCs转运钾的影响大于对专一性钾通道的影响;而较低温度(20℃)对专一性钾通道活性的抑制比对NSCCs的抑制更强。重金属镉和铜均对小麦的钾吸收速率产生影响,浓度越大,抑制作用越强。其中,根系NSCCs对镉的敏感度相对于专一性钾通道来说要低,而对铜的敏感度相对较高。说明不同重金属对两类通道蛋白的影响机制不一样。     

Effects of Supplemental Calcium on Ion Accumulation,Transport and Plant Growth of Salt Sensitive Brassica Rapa Landrace

ABSTRACT

Effects of three supplemental calcium (Ca⁺⁺; 2.5, 5.0, and 10 mole m^?3) concentrations on ion accumulation, transport, selectivity, and plant growth of salt-sensitive species, Brassica rapa ‘Sani’ in saline medium were investigated. Supplemental Ca⁺⁺ in the presence of 125 mol m^?3 sodium chloride (NaCl) did not improve the dry weight and leaf area indicating no role played by Ca⁺⁺ in the alleviation of salinity induced growth inhibition. However, calcium chloride (CaCl₂) did significantly affect sodium (Na⁺), potassium (K⁺), and Ca⁺⁺ contents of roots and shoots. The ion contents of shoots were significantly greater than those of roots per g dry weight, indicating ion transportation to shoots is greater than ion accumulation in roots. Use of CaCl₂ in 125 mol m^?3 NaCl reduced the Na⁺ content but increased K⁺ and Ca⁺⁺ contents in shoots. Sodium contents in shoots differed among the supplemental Ca⁺⁺ treatments indicating the role of CaCl₂ in Na⁺ ions transportation. Calcium content in shoots declined significantly in the control treatment (0 CaCl₂) but increased significantly in 10 mol m^?3 CaCl₂. The root also showed the effects of Ca⁺⁺ on the reduction of Na⁺ content and the increase of K⁺ and Ca⁺⁺ content. Unexpectedly, 5 mol m^?3 CaCl₂ induced the highest Na⁺ content in roots at 16 days after treatment. Supplemental CaCl₂ application influenced the K⁺ or Ca⁺⁺ selectivity over Na⁺ in two ways, ion accumulation at roots and transport to shoots. However, high CaCl₂ treatments allowed greater Ca⁺⁺ selectivity over Na⁺ than low CaCl₂. Likewise, high supplemental CaCl₂ showed higher K⁺ selectivity over Na⁺ than low CaCl₂. A marked increase in K⁺ versus Na⁺ selectivity for the transport process occurred at 10 mol m^?3 CaCl₂ treatments. The roots and shoots exhibited higher K⁺/Na⁺ and Ca⁺⁺/Na⁺ ratios in high CaCl₂ treatment than in low. The results are discussed in context to supplemental Ca⁺⁺ concentrations, ions accumulation, transportation and selectivity of salt sensitive Brassica rapa cultivar.     

Comparison of various methods for the determination of inorganic species in airborne atmospheric particulates

The performance of various filters used for determining inorganic species (heavy metals, light metals, anions and ammonium ion) in airborne particulates was comparatively assessed. Filters used in the determination of Ca²⁺, Mg²⁺, Na⁺, K⁺, Fe³⁺, Zn²⁺, Pb²⁺, Cr³⁺, Ni²⁺, V (V), Mn²⁺ and Cd²⁺ were attacked by acid extraction (glass microfibre filters, GF/A), acid extraction and microwave oven digestion (quartz filters, QM-A), and muffle furnace calcination and microwave oven digestion (Whatman-41 cellulose filters, W-41). The behaviour of the different filters tested towards aqueous extraction for the determination of anions (Cl^?, NO ₃ ^? , SO ₄ ^? , ammonium ion and light metals (Ca²⁺, Mg²⁺, Na⁺ and K⁺) was also studied and the results obtained for the light metals were compared with those provided by acid attack. All metals except vanadium were determined by ICP-AES; cadmium, lead and vanadium were analysed for by GFAAS; anions were quantified by ion chromatography (SO ₄ ^? was also measured by ICP-AES); and ammonium ion was determined by the Indophenol Blue method.     

K-priming positively modulates growth and nutrient status of salt-stressed cotton (Gossypium hirsutum) seedlings

Being macronutrient, K⁺ is involved in a number of metabolic processes including stimulation of over 60 enzymes. The present study was conducted to investigate whether K-priming could alleviate the effects of salinity on the growth and nutrient status of cotton seedlings. The seeds of two cotton cultivars, namely FH-113 and FH-87, were primed with solutions of three potassium sources (KNO₃, K₂SO₄ and K₂HPO₄) using three concentrations (0%, 1.25% and 1.5%) of each potassium source. After 1 week of germination, the seedlings were subjected to salinity (0 and 200 mM NaCl) stress. The results showed that salinity significantly affected growth and nutrients status of cotton seedlings. The K-priming alleviated the stress condition and significantly improved dry matter as well as nutrient uptake in cotton seedlings. Of the priming treatments pre-sowing treatment with KNO₃ (1.5%) was most effective in increasing shoot and root lengths and biomass of cotton seedlings. The seedlings raised from seed treated with KNO₃ (1.5%) showed varied accumulation of cations (Ca²⁺, Na⁺ and K⁺) and faced less oxidative stress irrespective of cotton cultivars under salt stress. The results suggested that pre-sowing seed treatment with KNO₃ (1.5%) might be recommended for synchronized germination and sustainable production of cotton crop under saline environments.     

Nitrate assimilation and biomass production in Sesamum indicuml. Seedlings in a lead enriched environment

Seed germination was delayed and seedling growth inhibited by 0.04 to 1.9 mM Pb⁺² in Sesamum indicum L. var HT-I. In root, shoot and leaf Pb⁺² accumulation increased with increasing Pb⁺² concentration in the nutrient solution. In root and leaf tissues in vivo and in vitro nitrate reductase activity was inhibited significantly which was well correlated with the concentration of Pb⁺² supplied and its accumulation in the plant parts. The inhibition of the NR enzyme activity could be, however, reversed by simultaneous treatment of Sesamum seedlings with K₂HPO₄, CaCl₂ and KNO₃ dissolved in nutrient solution. Total organic N and soluble protein of roots and shoots/leaves, on the other hand, increased with increasing concentration of Pb⁺² while the same treatment caused a decrease in the N content of cotyledons. It appears therefore, that the increase in N and protein in the roots, shoots/leaves may be a result of increased translocation of N from the cotyledons to the roots and shoots/leaves during early seedling growth in a Pb⁺² enriched environment.     

Growth and ion uptake of four Brassica species as affected by Na/Ca ratio in saline sand culture

The influence of supplemental Ca² in saline nutrient solutions on germination, growth, and ion uptake of four Brassica species, B. campestris L., B. carinata, A.Br., B. juncea (L.) Czern. and Coss., and B. napus L. was studied in sand culture. The addition of 11.25 mM CaC1² to nutrient solution containing 225 mM NaC1 improved percentage of germination of B. napus and B. juncea, but had no significant effect on the germination speed of the four species. There was no significant effect of additional amount of Ca² in the saline medium (150 mM NaC1) on the shoot biomass and seed yield of B. carinata and B. campestris. By contrast, shoot dry matter of B. napus and B. juncea increased significantly with the increased in Ca² concentration of the growth medium, but their seed yield remained unaffected. Decreased Ca² concentrations of the saline growth medium reduced percent oil content in B. carinata, B. juncea, and B. campestris. Increasing Na/Ca ratio of the external medium affected ion uptake differently in different species. In B. carinata, a relatively salt-tolerant species, the concentrations of Na⁺ and K⁺ in the shoots remained unaffected, but the C1 concentration was reduced linearly with the increase in external Na/Ca ratios. Root K⁺ and Ca²⁺ of the species decreased with the decrease in Ca²⁺ supply. In B. campestris increasing Na/Ca ratios of the saline medium had no effect on the concentrations of Na⁺, C1, and Ca²⁺ in the shoots and Na⁺, C1, and K⁺ in the roots. Only shoot K⁺ and root Ca²⁺ decreased consistently. In the highly salt-sensitive species, B. napus, the shoot Na⁺ was reduced by the addition of Ca²⁺ in the salt treatment, whereas the C1 and Ca²⁺ uptake was promoted by supplemental Ca²⁺. The root K⁺ concentrations decreased with the increase in Na/Ca. In B. juncea, which was similar to B. napus in biomass production, high Ca²⁺ concentration in the salt treatment reduced the shoot Na⁺ and root C1 concentrations and promoted the K⁺ uptake. Shoot Na/Ca and Na/K ratios were increased in B. napus and B. juncea at the highest Na/Ca ratio of the growth medium. Shoot K⁺ selectivity, S^K,Na (determined as molar ratio of K: Na in tissue to molar ratio of K:Na in external medium) of all species remained unaffected except for B. juncea in which it decreased significantly at the highest Na/Ca ratio. The root K⁺ selectivity increased in B. carinata.     

Elemental bioavailability in nutrient solutions in relation to precipitation reactions

In hydroponic plant nutritional research, nutrient solutions can be considered as aqueous solutions of inorganic ions. In this aqueous solution, the ions are submitted to the laws of aquatic inorganic chemistry. This means that the ions are involved in the dynamic equilibria between complexation, dissociation, and precipitation reactions. These chemical reactions seriously impact elemental speciation and bioavailability. As a result, plant roots experience a different nutritional composition. Ions withdrawn from the‐nutrient solution due to precipitation reactions, change the nutritional composition and are not available for uptake by plant roots. Like complexes, precipitates can buffer a nutrient solution, exchanging nutrients as these decrease by plant uptake. This research looks into the precipitation reactions that occur in hydroponic nutrient solutions. In the concentration range of nutrient solutions, no precipitates are formed involving potassium (K⁺), nitrate (NO₃ ^‐), ammonium (NH₄ ⁺), or sulphate (SO₄ ^2‐), while calcium (Ca²⁺) and magnesium (Mg²⁺) form mainly at a higher pH precipitates with hydrogen phosphate (HPO₄ ^2‐). Preparing nutrient solutions with tap water, calcium carbonate (CaCO₃) is likely to precipitate. A good knowledge of the chemical reactions occurring in nutrient solutions is the first prerequisite in hydroponic plant nutritional research.     

Biofiltration of Toxic Elements by Azolla Biomass

The aquatic fern Azolla binds heavy metals in a widerange of concentrations with high effectiveness, and it can therefore be used for the decontamination of polluted solutions.We have tested the application of its biomass as a practicalbiofilter for industrial waste treatment. In this report, we describe the properties of Azolla biomass which has been dried, rewetted and packed in columns, for use as an ion-exchange matrix. We used scanning electron microscopy in conjunction with an elemental analysis of the Azolla biomass to investigate its structure and to localize exchangeablecations. Azolla elemental content and model solutions containing Sr²⁺ eluted through the biofilter were analyzed.The Azolla biofilter bound Sr²⁺ ions efficientlyby ion exchange with K⁺, Na⁺, Ca²⁺ and Mg²⁺. K⁺ and Na⁺ ions were eluted during the initial phaseof Sr²⁺ binding, due to their lower affinity to the cation-binding groups in the Azolla cell wall. Ca²⁺ and Mg²⁺, bound with a higher affinity to theAzolla cation-binding groups, were exchanged during the secondary phaseof Sr²⁺ binding. Pre-loading of the metal-binding groups with K⁺ increased the removal of heavy metals from solutionby the Azolla biofilter. Our observations explain the mechanism of heavy-metal adsorption to the Azolla matrix.     

Diurnal Macronutrients Uptake Patterns by Lettuce Roots under Various Light and Temperature Levels

In order to reduce nutrient wastes to the environment the supply should be in accordance to the demand for these. Two experiments were conducted to study and quantify the effect of temperature, irradiance, and plant age on the uptake of nitrate (NO₃^?), ammonium (NH₄⁺), dihydrogen phosphate ion (H₂PO₄^?), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and sulfate (SO₄²). In the first experiment, various levels of temperature and irradiance were applied to plants in a growth chamber, while in the second experiment the uptake was studied along the crop season under greenhouse conditions. The uptake rates were calculated at 2-hour intervals through sampling the nutrient solution and analyzing it by inductively coupled plasma atomic emission spectrometry (ICP-AES). Increasing light and temperature enhance the uptake rates, while the rates decrease with plant age. Nitrogen absorption was similar during the day as during the night. No differences were found in the absorption of H₂PO₄^?, K⁺, Ca²⁺, Mg²⁺, and SO₄^2? between day and night. Nitrate absorption was found to have a positive correlation with the absorption of all the ions except for NH₄⁺.     

Uptake of cations by annual ryegrass as related to cations adsorbed onto root exchange sites

Abstract

Previously published results on exchange capacities for Ca²⁺, Mg²⁺, Mn²⁺, and K⁺ in the Donnan free space of roots of two ryegrass cultivars (Lolium multiflorum Lam. cv. Marshall and Wilo) grown at two Al levels in the nutrient solution (0 and 74 μM) were correlated with the average net uptakes of the same cations. For Al‐treated plants regressed separately, significant correlations r=0.906 and r=0.963 were found for Mn²⁺ and Ca²⁺/Mg²⁺, respectively. No significant correlations were observed for these cations in control plants. In contrast, when data of control and Al‐treated plants were combined, significant linear correlations r=0.805, r=0.924, and r=0.968 were found for Ca²⁺, K⁺, and K⁺/(Ca²⁺+Mg²⁺)^1/2, respectively. The influence of cations adsorbed onto the root exchange sites and the effect of Al on the cation uptake processes were discussed.     

Salt effects on growth and mineral contents of Diplachne fusca (Kallar grass)

Effects of NaCl, KC1, and CaCl₂ alone, and in combinations of NaCl/KCl and NaCl/CaCl₂ on growth and ion uptake by ‘Kallar'grass in soil and in solution cultures were studied. In soil up to 150 mM NaCl and KCl had little effect on growth but CaCl₂ depressed growth strongly. Dry weights in 150 mM NaCl/KCl decreased but remained little affected in NaCl/CaCl₂. Plant response to Na⁺ was little affected by Ca⁺⁺ or K⁺ and no interactions between Na⁺ and Ca⁺⁺ or Na⁺ and K⁺ were observed. Plant tissue exhibited a strong selectivity for K⁺ over Na⁺ Concentrations of Na and Cl in the tops exceeded those in the roots. Leaf transections are presented providing some information on the tissue anatomy.     

硅对植物体中某些营养物质穿细胞及质外体吸收的影响

The positive effects of silicon（Si） on growth of plants have been well documented;however,the impact of Si on plant nutrient uptake remains unclear.The growth,nutrient content and uptake of wheat（Triticum aestivum L.）,canola（Brassica napus L.） and cotton（Gossypium hirsutum L.） plants were evaluated with or without application of 1.5 mmol L^-1 Si.Application of Si increased dry weights by 8%,30%and 30%and relative growth rate（RGR） by 10%,13%and 17%in the cotton,canola and wheat plants,respectively.The plant relative water content（RWC） was also increased,but the plant transpiration was decreased by Si application.The uptake and content of Ca²⁺ were 19%and 21%lower in the cotton and wheat plants with Si than those without Si,respectively;however,Si application increased both K⁺ and Fe uptake and contents in all plant species.Silicon application reduced B uptake and content only in cotton and increased P and Zn²⁺ contents in all three plant species.The decrease in Ca²⁺ uptake by Si application was sustained even in the presence of metabolic inhibitors 2,4-dinitrophenol and sodium cyanide.Uptake of Ca²⁺ by Si application was enhanced or did not change when plant shoots were saturated with water vapor or their roots were exposed to low temperature.Thus,Si application increased the uptake of transcellularly transported elements like K⁺,P,Zn²⁺ and Fe.In contrast,Ca2+ uptake which occurred via both apoplastic and transcellular pathways was decreased by Si application,possibly through reduction of apoplastic uptake.More efficient nutrient uptake might be another promoting effect of Si on plant growth.     

Effect of different macronutrient cation ratios on macronutrient and water uptake by melon (Cucumis melo) grown in recirculating nutrient solution

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.     

盐胁迫下外源钙对高羊茅种子萌发和幼苗离子分布的影响

该文模拟了上海市临港新成陆地盐渍化土壤的盐分特点,并在100 mmol/L NaCl盐胁迫下,以常见牧草和草坪草高羊茅（Festucaarundinacea）为材料,在人工气候室可控制条件下,进行了盐胁迫下种子萌发和幼苗盆栽试验,用不同浓度的CaCl2（5、10、20、40、80 mmol/L）处理,研究高羊茅种子萌发和幼苗生长状况,重点研究了矿质元素Na^＋、K^＋、Ca^2＋和Mg^2＋在植株地上部分和地下部分的分布。研究表明：适当浓度的外源CaCl2浸种处理能缓解高羊茅种子受到的盐胁迫伤害,促使种子提前萌发,20 mmol/L CaCl2浸种处理能显著提高种子萌发率,但高浓度（80 mmol/L）的外源钙处理对高羊茅种子萌发不利;适当浓度的CaCl2处理能促进幼苗地上部分生长,降低高羊茅根冠比、稳定植物细胞膜、维持离子平衡、提高植物耐盐性,但是高浓度（80 mmol/L）CaCl2处理会对植物幼苗生长造成伤害。     

Nitrate Reduction and Nutrient Accumulation in Wheat Grown in Soil Salinized with Four Different Salts

ABSTRACT

The effect of salinization of soil with Na₂SO₄, CaCl₂, MgCl₂, and NaCl (70:35:10:23) on the biochemical characteristics of three wheat (Triticum aestivum L.) cultivars (‘LU-26S,’ ‘Sarsabaz’ and ‘Pasban-90’) was investigated under natural environmental conditions. Twenty-day-old seedlings of all three cultivars were subjected to three salinity treatments: 1.3 (control), 5.0, and 10 dSm^?1 for the entire life period of plants. After 120 d of seed sowing, plant biomass production decreased by 49% and 65%, respectively, in response to 5 and 10 dSm^?1 salinity levels. Addition of salts to growth medium also had a significant adverse effect on plant height. Increasing salinity treatments caused a great reduction in nitrate reductase activity (NRA) of the leaf. The inhibitory effect of salinity on nitrate reduction rate was more pronounced at the reproductive stage than at the vegetative stage of plant growth. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ showed less reduction in NRA due to salinity compared with ‘Pasban-90.’ Ascending salinity levels significantly reduced potassium (K⁺) and calcium (Ca²⁺) accumulation in shoots, while the concentration of sodium (Na⁺) was increased. Salts of growth medium increased the shoot nitrogen (N) concentration, whereas phosphorous (P) concentration of shoots was significantly reduced due to salinity. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ proved to be the salt-tolerant ones, producing greater biomass, showing less reduction in NRA, maintaining low sodium (Na⁺), and accumulating more K⁺ and Ca²⁺ in response to salinity. These two cultivars also showed less reduction in shoot K⁺/Na⁺ and Ca⁺/Na⁺ ratios than in ‘Pasban-90,’ particularly at the 10 dSm^?1 salinity level.     

SPECIFIC ION EFFECTS ON THE SEED GERMINATION OF SUNFLOWER

Salinity can affect germination of seeds either by creating osmotic potentials that prevent water uptake or by toxic effects of specific ions. This work was carried out to evaluate the germination of sunflower (Helianthus annuus L.) seeds under increasing salinity by using the most abundant salts in China. Potassium (K⁺), sodium (Na⁺), and calcium (Ca²⁺) contents in hypocotyls were determined on the fifth day. At same concentration of salt solution, the adverse effect of ions is in the following sequence: carbonate radical (CO₃ ^2?) > sulfate radical (SO₄ ^2?), chloride (Cl^?) > bicarbonate radical (HCO₃ ^?), magnesium (Mg²⁺) > Ca²⁺, and Na⁺ > K⁺. The effect of salinity on the germination phase of development is mainly due to its osmotic component other than the ion toxicity. Calcium decreased as increasing of the concentration of salt solutions, and cannot act as the role of enhancing cell division and membrane permeability.     

Responses of barley to hypoxia and salinity during seed germination,nutrient uptake,and early plant growth in solution culture

The resistance of most plants to salt can be impaired by concurrent waterlogging. However, few studies have examined this interaction during germination and early seedling growth and its implications for nutrient uptake. The aim of the study was to examine the response of germination, early growth, and nutrient uptake to salt (NaCl) and hypoxia applied to barley (Hordeum vulgare L. cv. Stirling), in solution culture. Hypoxia, induced by covering seeds with water, lowered the germination from 94% to 28% but salinity and hypoxia together lowered it further to 13% at 120 mM NaCl. While the germination was 75% at 250 mM NaCl in aerated solution, it was completely inhibited at this NaCl concentration under hypoxia. Sodium ion (Na⁺) concentrations in germinated seedlings increased with increasing salinity under both aerated and hypoxic conditions during germination, while K⁺ and Mg⁺ concentrations were decreased with increasing salinity in 6 d old seedlings. After 20 d, control seedlings had the same dry weights of the roots and shoots with and without hypoxia but at 10 mM NaCl and higher, shoot and root dry weight was depressed with hypoxia. Sodium ion increased in roots and shoots with increased NaCl under both aerated and hypoxic conditions while K⁺ was depressed when salinity and hypoxia were applied together and Ca²⁺ was mostly decreased by NaCl. In general, hypoxia had greater effects on nutrient concentrations than NaCl by decreasing N, P, S, Mg, Mn, Zn, and Fe in shoots and by increasing B concentrations. The threshold salinity levels decreased markedly for germination, uptake of a range of nutrients, and for seedling growth of barley under hypoxic compared to well‐aerated conditions.     

Sodium‐induced calcium deficiency in sugar beet during substitution of potassium by sodium

Functions of sodium (Na⁺) and potassium (K⁺) are closely associated. In some crops, Na⁺ is able to prevent or reduce considerably the occurrence of K⁺ deficiency. Sugar beet (Beta vulgaris L.) is a natrophilic crop, and positive effects of Na⁺ applications on yield were observed when K⁺ was sufficiently supplied. However, it is not known which specific function of K⁺ can limit the growth of sugar beet when K⁺ is substituted by an equivalent amount of Na⁺. Therefore, K⁺ substitution by Na⁺ was investigated for sugar beet in hydroponics. Surprisingly, no K⁺‐deficiency symptoms were observed. However, calcium (Ca²⁺) concentrations in the leaves were significantly decreased. Moreover, Ca²⁺ uptake and translocation through xylem sap were reduced in Na⁺‐treated plants. It is concluded that Ca²⁺ uptake by roots and its translocation via xylem sap primarily limit the possibility of K⁺ substitution by Na⁺ in sugar beet nutrition.