盐害生理与植物抗盐性

概述了盐害对植物的伤害及植物耐盐的生理机制,并综述了植物耐盐相关基因的研究进展。同时综合相关资料,提出了提高植物耐盐性的途径。     

生物炭调控盐胁迫下水稻幼苗耐盐性能

土壤盐渍化降低土壤生产力.探索生物炭对盐胁迫下水稻幼苗耐盐性能的影响,对调控盐渍区水稻生产潜力具有重要意义.本研究通过生物炭介入盐胁迫稻田土壤的盆栽试验,调查了生物炭对盐胁迫下土壤环境和水稻幼苗耐盐性能的影响.盐胁迫设置4个水平,分别为0 g NaCl·kg-1土(S0),1 g NaCl·kg-1土(S1),2 g ...     

Conservation of salt lakes

Salt lakes have a variety of important uses and values, including especially both economic and scientific ones. These uses and values have been and are increasingly subject to degradation from a variety of impacts: diversion of inflows, pollution, agricultural practices, and introduction of exotic species are among the more important. Recognition of these impacts upon salt lakes has led to some international and national measures for their conservation, but considerably more effort in this direction is needed. Against this background, Mono Lake, California, USA, and the Aral Sea, central Asia, are discussed as two localities which bring into sharp focus the various matters discussed in the paper. Finally, attention is drawn to the need to conserve the Akrotiri Salt Lake, Cyprus.     

Short-term salt tolerance mechanisms in differentially salt tolerant tomato species

The physiological changes induced by a daily increase of NaCl level, over a period of 4 d, were studied in leaves of the salt-sensitive cultivated tomato species Lycopersicon esculentum and its wild salt-tolerant relative Lycopersicon pennellii. A higher solute contribution to the osmotic adjustment was observed in NaCl-treated leaves of L. pennellii than in those of L. esculentum. This response together with the higher accumulation of inorganic solutes in the wild species and of organic solutes in the cultivated species verified the different salt tolerance mechanisms operating in the two species in the short-term. With regard to the changes induced by salt stress on the free polyamine levels, the putrescine and spermine levels increased with salinity, whereas the spermine levels decreased in both tomato species; nevertheless, the main difference between the two species lays in an earlier and greater accumulation of putrescine induced by salinity in L. pennellii than in L. esculentum. The changes in putrescine levels were associated to changes in amino acids related to its synthesis, and the changes were different in both species. In L. esculentum, the high concentrations of some intermediate compounds (glutamate and arginine) were related to the low accumulation rate of both proline and putrescine. In contrast, in L. pennellii, important reductions in glutamate and arginine levels were found at the end of the salinization period. Moreover, in this last situation, a decline in the putrescine level ran parallel to a high proline accumulation, which suggests that the higher the stress level, the higher the deviation of glutamate to proline occurring in the salt tolerant species. It could be concluded that an early accumulation of the diamine putrescine seems to be associated with salt tolerance in the short-term.     

Nucleation and facilitation in salt pans in Mediterranean salt marshes

Abstract. Arthrocnemum macrostachyum is a perennial species acting as a primary colonizer of salt pans in Mediterranean high salt marshes. Salicornia ramosissima, an annual, occurs in salt pans under Arthrocnemum canopies and in open areas. The aim of this study was to analyse, in wild populations and a transplant experiment, how S. ramosissima population dynamics and growth are affected by A. macrostachyum. The environmental conditions within the patches of Arthrocnemum were less stressful than in the open areas, with lower radiation levels and salinity concentrations. In the inner areas of A. macrostachyum patches, density‐dependent mortality processes of S. ramosissima seedlings led to low densities of adult individuals with greater morphological development and reproductive success than in open areas. However, at the edges of Arthrocnemum patches facilitation of seedling survival favoured high densities. Environmental stress hindered development, decreased reproduction and premature death. These results are in agreement with the general theory of factors controlling vegetation distribution that biotic interactions dominate in low stress environments, while abiotic interactions dominate under harsher environmental conditions. A. macrostachyum plays an essential role in the succession in these salt pans, facilitating seed production and stimulating nucleation processes in S. ramosissima.     

宏基因组学应用于耐盐酶类及耐盐基因研究的进展

耐盐酶在高盐浓度下仍具备催化活性和稳定性,在高盐食品和海产品加工、洗涤及其它高盐环境生物技术领域被广泛应用;耐盐基因在高盐条件下可以使微生物维持正常功能,获取并研究不同环境中的耐盐基因对揭示微生物的耐盐机制,以及实现其在高盐环境中的定向应用具有的重要意义。宏基因组学避开纯培养技术探知微生物的多样性及其功能,为我们提供了一种发现新基因、开发新的微生物活性物质和研究微生物群落结构及其功能的新技术。文中结合本课题组的研究工作,综述了利用宏基因组学获取耐盐酶类及耐盐基因的策略,同时着重介绍利用宏基因组学从海洋、土壤、胃肠道等环境中获取耐盐酶类及耐盐基因的研究。     

Vegetative salt tolerance of barnyard grass mutants selected for salt tolerant germination

Improving salt tolerance of economically important plants is imperative to cope with the increasing soil salinity in many parts of the world. Mutation breeding has been widely used to improve plant performance under salinity stress. In this study, we have mutagenized Echinochloa crusgalli L. with sodium azide and three selected mutants (designated fows A) with salt tolerant germination. Their vegetative growth was compared to that of the wild type after short-term and long-term salt stress. The germination of the three fows A mutants in the presence of inhibitory concentrations of NaCl, KCL, and mannitol was better than that of the wild type. Early growth of the mutants in the presence of 200 mM NaCl was also better than that of the wild type perhaps due to improved K⁺ uptake and enhanced accumulation of sugars particularly sucrose at least in two mutants. But the three mutants and the wild type responded similarly to long-term salt stress. The tolerance mechanisms during short-term and long-term salt stress are discussed.     

Plant salt tolerance

Soil salinity is a major abiotic stress in plant agriculture worldwide. This has led to research into salt tolerance with the aim of improving crop plants. However, salt tolerance might have much wider implications because transgenic salt-tolerant plants often also tolerate other stresses including chilling, freezing, heat and drought. Unfortunately, suitable genetic model systems have been hard to find. A recently discovered halophytic plant species, Thellungiella halophila, now promises to help in the detection of new tolerance determinants and operating pathways in a model system that is not limited to Arabidopsis traits or ecotype variations.     

Glycophyte salt resistance

By perfusion of entire sunflower stems with NaCl solutions of various concentrations, we studied the phenomenon of sodium decrement, i.e., sodium retaining in the stem and leaf petioles. Such retaining could comprise up to 50–80% of initial sodium concentration. It depended on the rate of perfusion, the length of xylem vessels, and NaCl concentration. When perfusion with 100–500 mM NaCl concentrations (high for glycophytes) lasted for 10–12 days, we did not observe any decrease in the degree of sodium decrement. Simultaneously with sodium decrement, other ions (K⁺ and Ca²⁺) were secreted into the perfusate, thus providing for physiological equilibrating the monosalt solution supplied to the stem base. The high salt concentration in the perfusate induced a decrease in the hydraulic conductance of the vessels. The conclusion is that stressful NaCl solutions attain the shoot meristem and reproductive organs as an “equilibrated” salt solution and at a declined rate of xylem flow. The mechanisms of observed phenomenon of glycophyte salt resistance are discussed, the main of them being related to osmosis-dependent responses of stem living cells and the processes of ion exchange between the cells and xylem vessel content.     

Bile salt evolution

Viewed against the background of known or supposed biosynthetic pathways for cholic and chenodeoxycholic acids in man and laboratory animals, the chemical nature of bile salts in more primitive animals clearly indicates that evolution from C(27), 5alpha-alcohol sulfates to C(24), 5beta-acids has taken place. Stages in this evolution, some of which are intermediates in the biosynthesis of C(24) bile acids, are described for representatives of all the chief vertebrate groups. "Unique" primary C(24) bile acids may be considered as hydroxylated chenodeoxycholic acids; the possible taxonomic significance of these is discussed. A closer study of the biochemical mechanisms underlying bile salt differences may be expected to throw new light on the nature of the evolutionary process itself.     

Measurement of the diffusion coefficient for salt in salt flat and mangrove soils

Excluded salt accumulated at mangrove roots must be transported away from the root zone by diffusive processes, due to the low permeability of most mangrove soils. The diffusion coefficient for salt in mangrove soils determines the rate of this diffusive transport but has not been determined experimentally before. In this work we used a 12-month long-time series of salt concentration profiles measured in a sediment core over which fresh water was continuously circulated, to determine the diffusion coefficient for salt in the soil. Salt concentrations were measured using an electrical conductivity probe that was developed for use in hypersaline (salt concentration up to and in excess of 120g/l) conditions. A modified formula was experimentally determined to relate electrical conductivity to salt concentration and temperature, applicable up to a salt concentration of 200g/l. This was done because standard formulae relating these variables do not apply in the hypersaline conditions often encountered in salt flat sediments. The salt concentration profiles were used in a simple mathematical model to determine a sediment diffusion coefficient for salt in a salt flat sediment. This value of D=(4.6±0.2) ×10^–5m²/day was approximately half that calculated theoretically.     

植物乳杆菌PUM1785抑菌作用及耐胆盐和耐盐性能

目的 通过分析植物乳杆菌PUM1785体外抑菌活性和部分耐受能力,为进一步研发乳杆菌微生态制剂提供理论和数据支持。 方法 以模式菌株WCSF1为对照株,采用双层琼脂点种法进行体外抑菌试验,并开展高胆盐、高盐环境耐受试验。 结果 植物乳杆菌PUM1785体外抑菌活性与模式菌株相近,对6种常见致病菌均有较强的抑制作用,对革兰阴性菌的抑菌效果优于革兰阳性菌。在不同浓度胆盐溶液中培养24 h后,2株乳杆菌生长均受抑制,当胆盐浓度从0 g/100 mL持续增至0.5 g/100 mL后,2株乳杆菌活菌数量呈下降趋势,但始终维持在105 CFU/mL数量级以上,并且PUM1785与WCSF1活菌数量比呈上升趋势;在不同浓度的NaCl溶液中培养24 h后,2株乳杆菌均生长良好,当NaCl浓度从0 g/100 mL升高到8 g/100 mL时,2株乳杆菌活菌数始终维持在108 CFU/mL数量级以上,并且PUM1785与WCSF1活菌数量比呈明显上升趋势。 结论 植物乳杆菌PUM1785具有与模式菌株相近的抑菌活性,对胆盐和高盐环境耐受力均强于模式菌株,表明PUM1785具有良好的生物学特性,可以作为微生态制剂研发的候选菌株。     

Dietary salt levels affect salt preference and learning in larval Drosophila

Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased. However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired. We test whether this surprising dissociation between the unconditioned and conditioned response depends on the larvae's experience of salt concentration in their food. We find that although the point at which a NaCl concentration becomes aversive shifts with different rearing experience, the dissociation remains evident. Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.     

Protective effect of the bile salt hydrolase-active Lactobacillus reuteri against bile salt cytotoxicity

 Bacterial bile salt hydrolysis is considered a risk factor for the development of colon cancer because of the risk of forming harmful secondary bile salts after an initial deconjugation step. In this study, the influence of enhanced bacterial bile salt transformation by the bile salt hydrolase-active Lactobacillus reuteri was studied in batch culture using the microbial suspension of the Simulator of the Human Intestinal Microbial Ecosystem; (SHIME), which was supplemented with oxgall at 5 g/l or 30 g/l. Changes in the fermentative capacity of the microbial ecosystem and the (geno)toxic properties of the SHIME supernatants were investigated. Increasing concentrations of oxgall inhibited the fermentation. Transient cell toxicity was observed for samples supplemented with 5 g oxgall/l, while samples with 30 g oxgall/l exhibited toxicity. The results of the haemolysis test suggest that the detrimental effects were probably due to the membrane-damaging effects of bile salts. In all cases, the adverse effects could be counteracted by the addition of 7.5 ± 0.5 log₁₀ CFU L. reuteri/ml. Plausible mechanisms for the protective properties of L. reuteri could involve a precipitation of the deconjugated bile salts and a physical binding of bile salts by the bacterium, thereby making the harmful bile salts less bioavailable. Received: 15 July 1999 / Received revision: 10 January 2000 / Accepted: 14 January 2000     

Overexpression of the wheat salt tolerance-related gene TaSC enhances salt tolerance in Arabidopsis

A novel gene named TaSC was cloned from salt-tolerant wheat. Northern blot showed that the expression of TaSC in salt-tolerant wheat was up-regulated after salt stress. Real-time quantitative PCR analyses showed that TaSC expression was induced by salt and ABA in wheat. Localization analysis showed that TaSC proteins were localized to the plasma membrane in transgenic Arabidopsis thaliana. The overexpression of TaSC in Col-0 and atsc (SALK_072220) Arabidopsis strains resulted in increased salt tolerance of the transgenic plants. TaSC overexpression in Col-0 and atsc signi?cantly up-regulated the expression of AtFRY1, AtSAD1, and AtCDPK2. AtCDPK2 overexpression in atsc rescued the salt-sensitive phenotype of atsc. The TaSC gene may improve plant salt tolerance by acting via the CDPK pathway.     

盐胁迫下囊果碱蓬出苗状况及苗期抗盐性

研究了盐胁迫对囊果碱蓬出苗、幼苗生长、离子积累以及光合放氧速率的影响.囊果碱蓬生长的最适盐浓度在200 mmol/L NaCl左右.高浓度NaCl(400 mmol/L和600 mmol/L)没有显著降低其出苗率,200 mmol/L NaCl对出苗率具有促进作用.400 mmol/L和600 mmol/L NaCl显著降低了光合放氧速率.囊果碱蓬在高浓度NaCl处理下能够维持叶片较高的K+/Na+ 及含水量可能是其适应高盐生境的重要机制.     

The salt relations of Dunaliella

Dunaliella tertiolecta (marine) and D. viridis (halophilic) were each trained by serial transfer to growth at salt concentrations previously regarded as the other's domain. D. viridis then had a salt optimum at 1.0–1.5 M sodium chloride whereas that for D. tertiolecta was less than 0–2 M. Nevertheless D. tertiolecta grew faster than the halophil at all salt concentrations up to 3.5 M, the highest at which they were compared.Both species accumulate glycerol, which is necessary for growth at elevated salinities and which responds in its content to water activity (a _w ) rather than specifically to salt concentration. Variation in glycerol content is a metabolic process which occurs in the dark from accumulated starch as well as photosynthetically. Regulation of glycerol content by a _w does not require protein synthesis. The NADP-specific glycerol dehydrogenase of each of the algae is likely to be directly involved in the regulation of glycerol content. Kinetic studies, together with those described in an earlier publication, show that the enzyme has regulatory properties, and that both glycerol and dihydroxyacetone act as effectors as well as reactants. A mechanism of the reaction is tentatively proposed.