Effect of ionic Al in culture solutions on the growth ofArnica montana L. andDeschampsia flexuosa (L.) Trin.

Summary Plants of five tomato strains were grown under low-K stress at three Na levels. These plants were harvested at three time intervals, and Na accumulation and distribution were measured in their tissues. Strain differences were observed for the ability to substitute Na for K under low-K stress. In two strains with high Na-substitution capacity, efficiency in substitution was associated with the accumulation of more Na and the maintenance of higher Na concentrations in shoot tissues than in other strains. In a third strain which also had a relatively high Na-substitution capacity at the highest solution Na level, an unusual efficiency in Na substitution was indicated, because the strain neither accumulated Na nor maintained high tissue Na levels.     

Isolation of tomato strains varying in potassium acquisition using a sand-zeolite culture system

One hundred tomato strains, representing widely diverse geographic areas, were evaluated in a sand-zeolite culture medium for their response to both low (0.25 mM) and adequate (1.0 mM) K levels. Three types of strains differing in K acquisition were classified: (1) efficient strains characterized by their ability to acquire K under low-K stress and with dry matter accumulation comparable to the strains grown under adequate-K supply, (2) inefficient strains that grew well under adequate-K supply but with a low capacity to acquire K at low-K stress and correspondingly lesser dry weight production, and (3) slowly growing strains featured by low K content in tissue and low dry matter accumulation irrespective of external K levels. The efficient and slowly growing strains came mostly from South and Central America, where tomato originated and was domesticated. Strains from other regions, however, mostly showed inefficiency in K acquisition. Two distinct features associated with the efficiency of K acquisition were identified. One was the proliferation of root length and another was high net K-influx rates per unit root length under low-K stress. Our results suggested that mechanisms for efficient acquisition of nutrients were lost during the cultivation of plants, and centers of plant origin and domestication contain valuable genetic resources for improving plant efficiency in nutrient acquisition.     

Salt resistance of chickpea genotypes in solutions salinized with NaCl or Na2SO4

Summary To assess the potential for developing a salt resistant cultivar of chickpea (Cicer arietinum L.) 160 genotypes were screened for percent survival after 9 weeks in greenhouse solution cultures, with 50 mM NaCl or 25 mM Na₂SO₄. All plants grew well in the sulfate treatment but only cv. L-550 survived the chloride treatment. Salt damage appeared and developed slowly. To check these apparent effects of cultivar and kind of anion, three genotypes including cv. L-550 were then grown in solutions with isoosmotic NaCl or Na₂SO₄ at three levels (−0.044, −0.088, and −0.132 MPa), and in a separate experiment cv. L-550 was grown with NaCl and Na₂SO₄ at four levels: 10, 20, 30 and 50 mM Na. Salt composition affected shoot weight less than salt level or cultivar did. Shoot dry weight was only slightly less in chloride treatments than in isoosmotic sulfate, and for the least sensitive cultivar (L-550) this held only at the highest salt level, corresponding to that in the screening trial. Further, sensitivity to sulfate and to chloride was equal when sodium concentrations in shoots were equal, regardless of anion compositions of media. Shoot Na concentration was a useful negative indicator of growth under salt stress regardles of cultivar, and may be a useful tolerance indicator also for other species that neither accumulate nor efficiently exclude Na.     

Modification of the salinity response of wheat by the genome ofElytrigia elongatum

Summary Triticum aestivum cv. Chinese Spring wheat,Elytrigia elongatum (tall wheatgrass), and theTriticum-Elytrigia amphiploid were grown in complete nutrient culture containing, in addition, 0, 40, 80 and 120 mM NaCl. The 3 genotypes responded quite differently to increasing salinity; the Na concentration of wheat shoots increased in direct proportion to the increase in salinity of the external medium whereas the Elytrigia response was interpreted as showing high affinity for Na at low external Na (40 mM) but comparative exclusion of Na at high salinities (120 mM). In contrast, Na levels of the amphiploid were less than those of either wheat or Elytrigia under both low and high salinities. Thus the amphiploid behaved like wheat at 40 mM NaCl but more like Elytrigia at 120 mM NaCl because Na transport to the amphiploid shoot was restricted over the whole salinity range. The K concentration of the amphiploid shoot at high salinities was significantly greater than the K concentrations of either wheat or Elytrigia.     

Response to NaCl of alfalfa plants regenerated from non-saline callus cultures

Salinity restricts crop productivity in many arid environments. Inadvertent selection for tolerance to osmotic stress may occur under cell or tissue culture conditions and could affect the performance of regenerated plants. The effect of NaCl on forage produced by alfalfa (Medicago sativa L.) plants regenerated from non-saline callus cultures was examined in this study. Plants of Regen-S, which was selected for improved callus growth and regeneration in non-saline cultures, had higher forage weight when grown on SHII medium at NaCl levels up to 100 mM compared to its parental cultivars, Saranac and DuPuits. Five additional original-regenerant plant pairs, each derived from non-saline callus cultures of different alfalfa plants, were evaluated in a solid (soil-like) substrate under saline and non-saline conditions. Weight of forage produced by rooted stem cuttings of regenerated plants was 33% higher at 50 mM NaCl compared to cuttings of explant donor plants. Self progenies from four of five regenerants had higher relative forage weight at 100 mM NaCl (percent of 0 NaCl treatment) than the original plants indicating increased NaCl tolerance.     

Soil moisture and potassium affect the performance of symbiotic nitrogen fixation in faba bean and common bean

Potassium (K) is reported to improve plant's resistance against environmental stress. A frequently experienced stress for plants in the tropics is water shortage. It is not known if sufficient K supply would help plants to partially overcome the effects of water stress, especially that of symbiotic nitrogen fixation which is often rather low in the tropics when compared to that of temperate regions. Thus, the impact of three levels of fertilizer potassium (0.1, 0.8 and 3.0 mM K) on symbiotic nitrogen fixation was evaluated with two legumes under high (field capacity to 25% depletion) and low (less than 50% of field capacity) water regimes. Plants were grown in single pots in silica sand under controlled conditions with 1.5 mM N (¹⁵N enriched NH₄NO₃). The species were faba bean (Vicia faba L.), a temperate, amide producing legume and common bean (Phaseolus vulgaris L.), a tropical, ureide producing species. In both species, 0.1 mM K was insufficient for nodulation at both moisture regimes, although plant growth was observed. The supply of 0.8 or 3.0 mM K allowed nodulation and subsequent nitrogen fixation which appeared to be adequate for respective plant growth. High potassium supply had a positive effect on nitrogen fixation, on shoot and root growth and on water potential in both water regimes. Where nodulation occurred, variations caused by either K or water supply had no consequences on the percentage of nitrogen derived from the symbiosis. The present data indicate that K can apparently alleviate water shortage to a certain extent. Moreover it is shown that the symbiotic system in both faba bean and common bean is less tolerant to limiting K supply than plants themselves. However, as long as nodulation occurs, N assimilation from the symbiotic source is not selectively affected by K as opposed to N assimilation from fertilizer.     

The presence of the enhanced K/Na discrimination trait in diploid Triticum species

Summary A number of accessions of the three species of diploid wheat, Triticum boeoticum, T. monococcum, and T. urartu, were grown in 50 mol m^-3 NaCl+2.5 mol m^-3 CaCl₂. Sodium accumulation in the leaves was low and potassium concentrations remained high. This was not the case in T. durum grown under the same conditions, and indicates the presence in diploid wheats of the enhanced K/Na discrimination character which has previously been found in Aegilops squarrosa and hexaploid wheat. None of the accessions of diploid wheat showed poor K/Na discrimination, which suggests that if the A genome of modern tetraploid wheats was derived from a diploid Triticum species, then the enhanced K/Na discrimination character became altered after the formation of the original allopolyploid. Another possibility is that a diploid wheat that did not have the enhanced K/Na discrimination character was involved in the hybridization event which produced tetraploid wheat, and that this diploid is now extinct or has not yet been discovered.     

Effect of salinity on soluble protein,free amino acids and nicotine contents inNicotiana rustica L.

Nicotiana rustica plants were grown under two grades of salinity conditions, 50 mM and 100 mM NaCl. High levels of NaCl added to the nutritive solution produced a progressive absorption of Na in detriment of K, thereby causing an ionic disequilibrium, particularly in leaves. The weight and longitudinal growth of plants grown under salinity conditions were lower than control plants, while their protein content was higher. Deficit of K induced by salinity increased the levels of free amino acids, especially of aspartic acid, glutamic acid and proline. On the other hand, the levels of nicotine in leaves of treated plants were lower than controls. In contrast, treatment of the plants with 100 mM NaCl induced in general an increase of nicotine in the roots. These results indicate that there was an unclear effect of salinity either on synthesis or on translocation of nicotine from roots to leves.     

The K/Na and Ca/Na ratios and rapeseed yield,under soil salinity or sodicity

Rapeseed (Brassica napus) is a crop relatively tolerant to salt and sodium. Our objective was to study the interactions between Na, K and Ca and their relationship with its yield under the isolated effects of soil salinity or sodicity.Two experiments were carried out using pots filled with the Ah horizon of a Typic Natraquoll. There were three salinity levels (2.3 dS m^-1; 6.0 dS m^-1 and 10.0 dS m^-1) and three sodicity levels, expressed as sodium adsorption ratios (SAR: 12; 27 and 44). The soil was kept near field capacity.As soil salinity increased, the K/Na and Ca/Na ratios in the tissues decreased markedly but yields and aerial biomass production were not affected. As soil SAR value increased, the K/Na and Ca/Na ratios in plants and K-Na and Ca-Na selectivities decreased. Plants could not maintain their Ca concentration in soil with a high SAR. The grain yield and biomass production diminished significantly in the highest SAR treatment. Our results are consistent with those showing detrimental osmotic effects of salts in Brassica napus. Conversely, under sodicity, the K/Na and Ca/Na ratios in plant tissues decreased considerably, in accordance with grain and biomass production. These results show that the effects of sodicity are different from those of salinity.     

The physiological basis of increased biomass partitioning to roots upon nitrogen deprivation in young clonal tea (Camellia sinensis (L.) O. Kuntz)

Deprivation of nitrogen (N) increases assimilate partitioning towards roots at the expense of that to shoots. This study was done to determine the physiological basis of increased root growth of tea (sCammellia sinensis L.) under N shortage. Nine-month-old clonal tea (clone TRI2025) was grown in quartz sand under naturally lit glasshouse conditions. Three levels of N (0, 3.75 and 7.5 mM N) were incorporated in to the nutrient solution and applied daily. Plant growth, photosynthesis, root respiration and plant N contents were measured at 10-day intervals over a 45-day period. Root dry weight showed a sharp increase during the first 15 days after the plants were transferred to 0 mM N, whereas no such increase was shown in plants transferred to 7.5 mM N. In contrast, shoot dry weight increased at 7.5 mM N and was significantly greater than at 0 mM N, where no increase was observed. Due to the above changes, root weight ratio increased and leaf weight ratio decreased during the first 15 days of N deprivation. Leaf photosynthetic rates did not vary between N levels during the initial 15-day period. Thereafter, photosynthetic rates were greater at 7.5 mM and 3.75 mM N than at 0 mM N. Root respiration rate decreased at 0 mM N, whereas it increased at 3.75 and 7.5 mM N, probably because of the greater respiratory cost for nitrate uptake. Root respiratory costs associated with maintenance (R _m) and nitrate uptake (R _u) were calculated to investigate whether the sharp increase of root growth observed upon nitrogen deprivation was solely due to the reduced respiratory costs for nitrate uptake. The estimated values for R _m and R _u were 3.241 × 10^–4 mol CO₂ g^–1 (root dry matter) s^–1 and 0.64 mol CO₂ (mol N)^–1, respectively. Calculations showed that decreased respiratory costs for nitrate uptake could not solely account for the significant increase of root biomass upon N deprivation. Therefore, it is concluded that a significant shift in assimilate partitioning towards roots occurs immediately following N deprivation in tea.     

Effect of CaSO4 and NaCl on mineral content ofLeucaena leucocephala

The effects of varying CaSO₄ and NaCl levels on the nutrient content ofLeucaena leucocephala were established by examining the concentrations of Na, Ca, Cl, K and Mg in leucaena roots, stems and leaves. Leucaena was grown in nutrient solution at four levels of CaSO₄ (0.5, 1.0, 2.5 and 5.0 mM) and NaCl (1, 25, 50 and 100 mM), in randomized blocks with five replications. Leucaena excluded sodium from stems and leaves when NaCl concentration was 50 mM or less. Sodium uptake decreased as CaSO₄ concentration increased. Calcium uptake was affected by NaCl concentration when substrate CaSO₄ concentration was 0.5 mM. At this level, 100 mM NaCl caused a marked decrease in leaf calcium and a marked increase in leaf Cl. In all other treatments, Cl uptake was not affected by CaSO₄ concentration. Potassium uptake was strongly depressed as NaCl concentration increased at low Ca concentration, but this effect was offset at high Ca. Magnesium uptake decreased as CaSO₄ levels increased.     

Interactive effects of boron and salinity stress on the growth,membrane permeability and mineral composition of tomato and cucumber plants

A greenhouse study was conducted in order to determine interactive effects of NaCl salinity and B on the growth, sodium (Na), chloride (Cl), boron (B), potassium (K) concentrations and membrane permeability of salt resistant Tomato (Lycopersicon esculentum L. cv. Lale F₁) and salt sensitive cucumber (Cucumis sativus L. cv. Santana F₁) plants. Plants were grown in a factorial combination of NaCl (0 and 30 mM for cucumber and 0 and 40 mM for tomato) and B (0, 5, 10 and 20 mg kg^–1 soil). Boron toxicity symptoms appeared at 5 mg kg^–1 B treatments in both plants. Salinity caused an increase in leaf injury due to B toxicity, but it was more severe in cucumber. Dry weights of the plants decreased with the increasing levels of applied B in nonsaline conditions, but the decrease in dry weights due to B toxicity was more pronounced in saline conditions especially in cucumber. Salinity × B interaction on the concentration of B in both plants was found significant. However, increase in B concentrations of tomato decreased under saline conditions when compared to nonsaline conditions. Contrary to this, B concentration of cucumber increased as a result of increasing levels of applied B and salinity. Salinity increased Na and Cl concentrations of both plants.Potassium concentration of tomato was not affected by salinity and B treatments, but K concentration of cucumber was decreased by salinity. Membrane permeability of the plants was increased by salinity while toxic levels of B had no effect on membrane permeability in nonsaline conditions. Membrane permeability was significantly increased in the presence of salinity by the increasing levels of applied B.     

Selection of balancing ions for nutritional studies in nutrient culture experiments

Nutrient culture studies frequently involve the use of balancing ions to equalize concentrations of essential nutrient elements. In a pot experiment in controlled environment with Lupinus angustifolius, growth and nodulation were assessed following calcium treatment (15 mM) using the acetate, chloride and sulphate salts in various combinations. Chloride depressed nodulation at levels higher than 20 mM; nodule mass and number were highest at the maximum sulphate concentration (13 mM). At the lowest sulphate level (2 mM), nodulation and root growth were depressed by 4 mM or higher acetate. Nodulation (dry weight and numbers of nodules) was maximized at 13 mM sulphate/4 mM chloride.     

盐胁迫对四种基因型冬小麦幼苗Na+、K+吸收和累积的影响

以4种不同基因型冬小麦品种为试验材料,研究了盐胁迫下小麦幼苗的生长及Na^＋、K^＋和Cl^-的吸收、累积规律。结果表明,盐胁迫下小麦吸水困难,幼苗生长受抑;幼苗含水量、生物量及干物质量明显下降;Na^＋、Cl^-含量和单株累积量显著增加。K^＋含量和单株累积量则明显降低。Na^＋／K^＋比值随介质中的盐浓度的增加而升高。盐胁迫下各基因型冬小麦幼苗Na^＋、K^＋和Cl^-的单株累积量及其在地上部分和根系中的含量变化较大,说明小麦根系对Na^＋、K^＋和Cl^-的吸收存在基因型差异。盐处理下,暖型小麦NR9405对K^＋的选择吸收能力强,对Na^＋的吸收和累积少,植株体内的K^＋浓度较高,Na^＋／K^＋比值小;幼苗的生物量较大,耐盐性强。冷型小麦RB6对K^＋的选择能力差,对Na^＋的吸收和累积量大,幼苗的Na^＋／K^＋比值大,生物量小,耐盐性较差。低盐浓度下,Na^＋可作为渗透调节物质维持植物体内渗透平衡。高盐浓度下,Na^＋的过度吸收和累积可能是盐害的主要原因。维持体内较低的Na^＋水平和Na^＋／K^＋比值是小麦耐盐性的一个重要特征。     

The ectomycorrhizal fungus Scleroderma bermudense alleviates salt stress in seagrape (Coccoloba uvifera L.) seedlings

The purpose of this study was to test the capacity of the ectomycorrhizal (ECM) fungus, Scleroderma bermudense, to alleviate saline stress in seagrape (Coccoloba uvifera L.) seedlings. Plants were grown over a range (0, 200, 350 and 500 mM) of NaCl levels for 12 weeks, after 4 weeks of non-saline pre-treatment under greenhouse conditions. Growth and mineral nutrition of the seagrape seedlings were stimulated by S. bermudense regardless of salt stress. Although ECM colonization was reduced with increasing NaCl levels, ECM dependency of seagrape seedlings increased. Tissues of ECM plants had significantly increased concentrations of P and K but lower Na and Cl concentrations than those of non-ECM plants. Higher K concentrations in the leaves of ECM plants suggested a higher osmoregulating capacity of these plants. Moreover, the water status of ECM plants was improved despite their higher evaporative leaf surface. The results suggest that the reduction in Na and Cl uptake together with a concomitant increase in P and K absorption and a higher water status in ECM plants may be important salt-alleviating mechanisms for seagrape seedlings growing in saline soils.     

Aluminum stress on sorghum growth and nutrient relationships

Summary Sorghum plants were grown in the greenhouse in modified Steinberg nutrient solution containing ten Al rates (0 to 297 μM) and harvested 28 days after transplanting. Top and root dry weight were not affected by added Al up to 74 μM; but decreased sharply at concentration of 148 μM and greater. Aluminum concentrations in blade 1 (recently matured blade) and plants remained constant from 0 to 297 μM added Al. Root Al concentration increased as added Al increased. No correlation existed between top dry weight and Al concentration in blade 1 or in plant. Root Al concentration was related to top dry weight and root dry weight to estimate the Al critical toxicity level. The Al critical toxicity levle in the root was 54 mmol kg⁻¹ root dry weight basis for either top or root dry weight. In blade 1 Cu concentration negatively correlated with Al while Fe and P were positively correlated. In roots Ca, Mg, Mn and Fe concentrations were negatively correlated with Al while Zn, Cu, P, and K were positively correlated with Al concentration.     

The effects of salinity on growth,nodulation and nitrogen fixation ofCasuarina equisetifolia

The growth, nodulation and nitrogen fixation ofCasuarina equisetifolia were compared at six levels (0–500mM NaCl) of salinity in sand culture. Dry weight of nodules, shoots and roots and N content of shoots increased at intermediate levels of salinity (50–100 mM) but decreased at 500 mM NaCl. Nodulation occurred at all NaCl levels, but at 500mM NaCl level, the nodule dry weight declined by 50% from the control. Increasing NaCl concentration of up to 200mM had little effect on the N₂-fixation rate, but at 500mM NaCl level the rate decreased to 40% of the control value.     

Salinity-calcium interactions on growth and ionic concentration of Citrus plants

Two-year-old Navel orange scions (Citrus sinensis (L.) Osbeck) budded to either Cleopatra mandarin (C. reticulata) and Troyer citrange (C. sinensis × P. trifoliata) rootstocks were used in this experiment. Cleopatra manda in rootstock was considered more tolerant to salinity than Troyer citrange, and this property was attributed to a greater capacity to exclude chloride ions.Plants were grown under glasshouse conditions and supplied with nutrient solution containing either no or 45 mM NaCl. Calcium concentration was increased from 3 to 30 mM. Sodium, potassium, calcium and chloride concentrations in plant organs were analyzed after 90 days of treatment.Supplemental Ca was found to mitigate the adverse effects of salinity on plant growth, defoliation or leaf injury.Chemical analysis indicated that in plants grafted on Troyer citrange Ca restricted uptake and subsequent translocation of Na to the leaves and increased K concentration in both roots and leaves. However, in Cleopatra mandarin-grafted plants increasing Ca levels seemed to reduce transport of Na from roots to leaves, and Na accumulation in roots was associated with reduced concentration of K in this rootstock.Organ chloride analysis showed that Cl accumulation in leaves of plants grafted on both rootstocks was reduced when external Ca concentration increased, whereas Cl concentration in roots remained constant or increased. The data of distribution of Cl in plants showed that a high external Ca level increased Cl accumulation in the basal stem and roots, and reduced the transport of Cl from roots to leaves.     

Cinnamate toxicity expression on phenylalanine ammonia-lyase activity,germination and growth of cucumber (Cucumis sativis) seedlings

Low pH (5.2) decreased nodule number and acetylene reduction. Aluminium further depressed those parameters in theRhizobium leguminosarum-Pisum sativum associations examined. In the Al-treated plants nodule formation by strains 128C53 and 128C30 was not affected by 3 or 15 and 30 or 60 μM Al, respectively, as compared with the number of nodules on plants grown at pH 5.2 in the absence of Al. However, improved nodulation rates by those strains did not enhance plant dry weight or reduced nitrogen content. No differences in nitrogenase activity were found among strains of nodulating plants grown at the same aluminium level. These results suggest that Al-ions affected specifically nitrogenase activity and that this effect was primarily responsible for the reduction in plant growth.     

Capacity of chromatiaceae for chemotrophic growth. Specific respiration rates of Thiocystis violacea and Chromatium vinosum

The capacity for chemoautotrophic, mixotrophic and organotrophic growth in the dark was tested with 45 strains of 17 species (11 genera) of the Chromatiaceae. The auxanographic deep agar shake culture method was used; the gas phase contained 5% O₂ and 1% CO₂ in N₂. All strains tested of Chromatium vinosum, C. minus, C. violascens, C. gracile, Thiocystis violacea, Amoebobacter roseus, Thiocapsa roseopersicina gave positive growth responses under chemoautotrophic and mixotrophic conditions (extra carbon source acetate); one strain of Thiocapsa roseopersicina grew also organotrophically on acetate alone. No growth was obtained with the remaining 17 strains of ten species. None of the five type species (three genera) of the Chlorobiaceae grew under chemotrophic conditions. With Thiocystis violacea 2311 a growth yield of 11.3g dry weight per mol thiosulfate consumed was obtained under chemoautotrophic conditions; under mixotrophic conditions with acetate the yield increased to 69g dry weight per mol thiosulfate consumed. With Thiocystis violacea 2311 maximal specific respiration rates were obtained with thiosulfate as electron donor irrespective of the presence or absence of sulfur globules in the cells; organic substrates served as carbon sources only and did not support respiration. With Chromatium vinosum D utilization of thiosulfate was not constitutive; maximal respiration rates on thiosulfate were obtained only with thiosulfate grown cells containing sulfur globules. Respiration rates were further increased by malate, fumarate or propionate; these substrates also served as sole electron donors for respiration. Acetate and pyruvate were used as carbon sources only. The ecological significance of the chemotrophic metabolism is discussed.