Overaccumulation of glycine betaine alleviates the negative effects of salt stress in wheat

To investigate the physiological mechanisms of glycinebetaine (GB) involved in the improvement of salt tolerance of wheat, three transgenic wheat (Triticum aestivum L.) lines-T1, T4, and T6-and the wild-type (WT) line Shi4185 were used. The transgenic lines were generated by introducing the BADH gene encoding betaine aldehyde dehydrogenase, which was cloned from Atriplex hortensis L. The BADH gene induced overexpression of GB in transgenic lines. Salt stress was induced by adding 200 mM NaCl, and the osmotic adjustment (OA), ion homeostasis, and antioxidant characteristics of wheat plants were observed. Under salt stress, the OA in the transgenic wheat lines was significantly higher than that in WT; this may be attributed to GB itself and/or the GB-induced overaccumulation of other osmolytes, such as free proline, soluble protein, and soluble sugar. Moreover, the transgenic lines could maintain the lower Na⁺ and Cl⁻ concentrations in their leaves by accumulating these ions in the sheaths in order to protect the leaves from ion toxicity; however, these lines maintained a higher K⁺ concentration in the leaves since K⁺ functions as an osmolyte and maintains ion homeostasis in the leaf cells. Furthermore, the in vivo overaccumulated GB could enhance or stabilize the activity of antioxidant enzymes that can scavenge reactive oxygen species (ROS) and mitigate oxidative damage of biomembranes. The experimental results suggest that GB overexpression can enhance the salt tolerance of transgenic plants by regulating ion homeostasis, enhancing OA, and scavenging ROS. Published in Russian in Fiziologiya Rastenii, 2009, vol. 56, No. 3, pp. 410–417. This text was submitted by the authors in English.     

Salt sensitivity in wheat : a case for specific ion toxicity

Two selected lines of bread wheat, Triticum aestivum L., differing in their relative salt resistance, were grown in isosmotic solutions of different ionic compositions to investigate sensitivity to specific ions. Growth rates and ion accumulation were determined. The salt composition of the various solutions had little effect on the growth of the salt-resistant line, but significantly affected that of the salt-sensitive line. Specifically, solutions containing high Na⁺ concentrations were more toxic than those containing high Cl⁻ concentrations or high concentrations of nutrient ions. There were few differences in ion accumulation between lines in a given treatment, although the sensitive line tended to accumulate more Na⁺ than the tolerant line in the salt treatments with high Na⁺ concentrations. The overall results provide evidence that there is a definite specific ion effect which is related to salt sensitivity in wheat. It is suggested that superior compartmentation of toxic ions, principally Na⁺, may be a mechanism of salt resistance in this case.     

抗旱性不同的小麦叶片的渗透调节与水分状况的关系

两年的试验结果表明：在土壤水分胁迫下抗旱性强的小麦品种叶片的相对含水量和水势均高于抗旱性弱的品种;渗透势与水势为线性关系,水势每变动一个单位,渗透势变动0.71- 0.93个单位;渗透势与相对含水量的对数化关系为两条直线组成的一条折线,第一条直线渗透势的下降完全由渗透调节引起;第二条直线渗透势下降主要是细胞失水浓缩的结果。渗透调节能力为：秦麦3号>昌乐5号>山农587>济南13>烟农15>鲁麦5号。     

Exploitation of synthetic-derived wheats through osmotic stress responses for drought tolerance improvement

The development of drought tolerant wheat cultivars has been slow due to lack of understanding the diagnostic physiological parameters associated with improved productivity under water stress. We evaluated responses to PEG induced osmotic stress under hydroponics in D-genome synthetic derived and bread wheat germplasm with the main aim to unravel and identify some promising attributes having role in stress tolerances. Genotypes used in this study differed in their morpho-physiological and biochemical attributes. Tolerant genotypes exhibited the ability to ameliorate harmful effects of PEG induced osmotic stress through better osmotic adjustment achieved through substantial relative water content (RWC), lowered osmotic potential, relatively stable root length having maximum water extraction capacity, significant increase in osmoprotectant concentration and relatively enhanced antioxidant activities. The results clearly revealed the importance of synthetic derivatives over check cultivars and conventional wheats in terms of osmotic stress responses. Interestingly, synthetic-derived advanced lines with Aegilops tauschii in its parentage including AWL-02, AWL-04 and AWL-07 proved superior over the best rainfed check cultivar (Wa-01). It was concluded that synthetic-derived wheats has great potential to improve a range of stress adaptive traits. It could, therefore, be recommended to be a useful strategy for allowing modern bread wheat to become adapted to a wider range of environments in future climate change scenarios.     

Plasticity in sunflower leaf and cell growth under high salinity

A group of sunflower lines that exhibit a range of leaf Na ⁺ concentrations under high salinity was used to explore whether the responses to the osmotic and ionic components of salinity can be distinguished in leaf expansion kinetics analysis. It was expected that at the initial stages of the salt treatment, leaf expansion kinetics changes would be dominated by responses to the osmotic component of salinity, and that later on, ion inclusion would impose further kinetics changes. It was also expected that differential leaf Na ⁺ accumulation would be reflected in specific changes in cell division and expansion rates. Plants of four sunflower lines were gradually treated with a relatively high (130 mm NaCl) salt treatment. Leaf expansion kinetics curves were compared in leaves that were formed before, during and after the initiation of the salt treatment. Leaf areas were smaller in salt‐treated plants, but the analysis of growth curves did not reveal differences that could be attributed to differential Na⁺ accumulation, since similar changes in leaf expansion kinetics were observed in lines with different magnitudes of salt accumulation. Nevertheless, in a high leaf Na⁺‐including line, cell divisions were affected earlier, resulting in leaves with proportionally fewer cells than in a Na⁺‐excluding line. A distinct change in leaf epidermal pavement shape caused by salinity is reported for the first time. Mature pavement cells in leaves of control plants exhibited typical lobed, jigsaw‐puzzle shape, whereas in treated plants, they tended to retain closer‐to‐circular shapes and a lower number of lobes.     

基于叶片生理指标的小麦芽期耐盐性评价

土壤盐渍化严重影响小麦生产,提高小麦耐盐性是应对土壤盐渍化的主要生物途径之一.小麦芽期亦是对盐分较为敏感的时期,小麦芽期耐盐性的强弱对盐碱地小麦种植至关重要.为探讨利用叶片生理指标进行小麦芽期耐盐性评价的可行性,该文以沧麦6005及其73个叠氮化钠诱变家系为试验材料,在超纯水和40％人工海水条件下,对芽期叶片中脯氨酸、...     

Improving salinity tolerance in crop plants: a biotechnological view

Salinity limits the production capabilities of agricultural soils in large areas of the world. Both breeding and screening germplasm for salt tolerance encounter the following limitations: (a) different phenotypic responses of plants at different growth stages, (b) different physiological mechanisms, (c) complicated genotype × environment interactions, and (d) variability of the salt-affected field in its chemical and physical soil composition. Plant molecular and physiological traits provide the bases for efficient germplasm screening procedures through traditional breeding, molecular breeding, and transgenic approaches. However, the quantitative nature of salinity stress tolerance and the problems associated with developing appropriate and replicable testing environments make it difficult to distinguish salt-tolerant lines from sensitive lines. In order to develop more efficient screening procedures for germplasm evaluation and improvement of salt tolerance, implementation of a rapid and reliable screening procedure is essential. Field selection for salinity tolerance is a laborious task; therefore, plant breeders are seeking reliable ways to assess the salt tolerance of plant germplasm. Salt tolerance in several plant species may operate at the cellular level, and glycophytes are believed to have special cellular mechanisms for salt tolerance. Ion exclusion, ion sequestration, osmotic adjustment, macromolecule protection, and membrane transport system adaptation to saline environments are important strategies that may confer salt tolerance to plants. Cell and tissue culture techniques have been used to obtain salt tolerant plants employing two in vitro culture approaches. The first approach is selection of mutant cell lines from cultured cells and plant regeneration from such cells (somaclones). In vitro screening of plant germplasm for salt tolerance is the second approach, and a successful employment of this method in durum wheat is presented here. Doubled haploid lines derived from pollen culture of F₁ hybrids of salt-tolerant parents are promising tools to further improve salt tolerance of plant cultivars. Enhancement of resistance against both hyper-osmotic stress and ion toxicity may also be achieved via molecular breeding of salt-tolerant plants using either molecular markers or genetic engineering.     

Intracellular compartmentation of ions in salt adapted tobacco cells

Na⁺ and Cl⁻ are the principal solutes utilized for osmotic adjustment in cells of Nicotiana tabacum L. var Wisconsin 38 (tobacco) adapted to NaCl, accumulating to levels of 472 and 386 millimolar, respectively, in cells adapted to 428 millimolar NaCl. X-ray microanalysis of unetched frozen-hydrated cells adapted to salt indicated that Na⁺ and Cl⁻ were compartmentalized in the vacuole, at concentrations of 780 and 624 millimolar, respectively, while cytoplasmic concentrations of the ions were maintained at 96 millimolar. The morphometric differences which existed between unadapted and salt adapted cells, (cytoplasmic volume of 22 and 45% of the cell, respectively), facilitated containment of the excited volume of the x-ray signal in the cytoplasm of the adapted cells. Confirmation of ion compartmentation in salt adapted cells was obtained based on kinetic analyses of ²²Na⁺ and ³⁶Cl⁻ efflux from cells in steady state. These data provide evidence that ion compartmentation is a component of salt adaptation of glycophyte cells.     

NaCl胁迫对小黄花菜生长及相关生理指标的影响

为探讨小黄花菜的耐盐机理,选育良好的耐盐植物以缓解土壤盐渍化问题,该文选取小黄花菜(Hemerocallis minor)为试材,采用砂培法,研究不同浓度NaCl(50、100、150、200、250 mmol·L-1)胁迫对小黄花菜的生长性状、细胞质膜透性和有机渗透调节物质含量等的影响.结果表明:(1)小黄花菜在10...     

Inheritance of osmotic adjustment to water stress in three grain sorghum crosses

Water stress is one of the major constraints to the grain yield of sorghum in tropical and sub-tropical areas of the world. Osmotic adjustment has been widely proposed as a plant attribute that confers adaptation to water stress. The inheritance of osmotic adjustment to water stress was investigated in a series of generations derived from the three possible bi-parental crosses between two inbred sorghum lines with a high capacity for osmotic adjustment (Tx2813 and TAM422; high-OA lines) and one with a low capacity (QL27; low-OA line). Broad-sense heritability on a single-plant basis was generally found to be high. Analysis of segregation ratios by the mixture method of clustering identified two independent major genes for high osmotic adjustment. The line Tx2813 possessed a recessive gene which is given the symbol oa1; the line TAM422 possessed an additive gene which is given the symbol OA2. There was some evidence that there may be other minor genes which influence the expression of osmotic adjustment in these crosses as two putative transgressive segregants, with higher osmotic adjustment than the parents, were identified from the cross between Tx2813 and TAM422. Populations of recombinant inbred lines were developed and characterised for osmotic adjustment for two of the crosses (QL27 x TAM422, low-OA x high-OA; Tx2813 x TAM422, high-oal x high-OA2). These will be used to conduct experiments which test hypotheses about the contribution of the high-osmotic-adjustment genes to the grain yield of sorghum under a range of water-stress conditions.     

不同倍性小麦对盐胁迫的适应性差异

植物染料在工业化应用过程中存在着资源限制,目标色相不丰富、色牢度不理想、植物染料本身的鉴别和成品的鉴别等问题。为了丰富染料植物资源的来源和提高染料植物资源的利用效率,该研究对西双版纳傣族利用的染料植物及其染色工艺涉及的相关植物进行了系统调查。2014年10月到2016年1月,采用半结构式访谈法对西双版纳14个村寨的56个关键信息人进行访谈,收集信息包括使用着色植物、媒染植物和助染植物的种类、傣名、利用部位和资源来历,以及预处理和染色过程工艺条件与技术步骤;采用参与式观察法对4种色相的10个染色工艺过程进行了记录,采集了凭证标本和图像资料;对调查信息进行了整理编目。结果表明：西双版纳地区的傣族使用11种着色植物和17种助染植物;目标色相有红、黄、蓝和绿。分析了傣族染料植物资源的发掘潜力、傣族利用植物染色对于染料植物利用的应用启发。该研究详细深入地记录了西双版纳傣族使用的染料植物的种类及其相关的组合和染色的过程。该研究结果对民族民间染料植物与染色工艺的产业化应用具有重要借鉴意义,为染料植物资源筛选及其染色工艺条件优化提供了参考。     

Silicon increases salt tolerance by influencing the two-phase growth response to salinity in wheat (Triticum aestivum L.)

Salt usually stresses plants in two ways, osmotic stress and ion toxicity. Plant responds to salinity in two distinct phases through time. It is known that silicon (Si) could alleviate salt stress by decreasing the Na⁺ accumulated in the leaf. In order to determine the function of Si in the two-phase growth response (osmotic and ion toxicity) to salinity, we selected the wheat cultivar “Changwu 134” out of 10 wheat cultivars, and confirmed that it responds to salinity in two distinct phases through time. The fresh weight, leaf area, and leaf Na⁺ concentration were measured during 31 days of 120 mM NaCl supplemented with 1 mM Si treatment. The results revealed that the growth of plants under salinity conditions both with and without Si application were in accordance with the two-phase growth model. Si alleviated the salt stress in the both two-phase growth, but the alleviative effects were more pronounced in the osmotic stress phase than ion toxicity phase. These results clearly showed that Si can enhance plant salt tolerance by alleviating the salt-induced osmotic stress.     

沼泽、盐化沙丘过渡带和沙丘生境下芦苇的光合及生理生化特性

对于田地区3种不同生境(沼泽、盐化沙丘过渡带和沙丘顶)芦苇的生长环境特征、光合特性、渗透调节及抗氧化系统的特征进行研究。结果表明:芦苇叶片的Pn日变化在沼泽生境呈单峰曲线,在盐化沙丘过渡带和沙丘顶部均为双峰曲线,光合"午休"现象明显,气孔导度降低是其主要原因。脯氨酸和可溶性糖含量随根区土壤水分减少和盐分加剧增加显著,其中可溶性糖含量变化剧烈,对抵御干旱和盐渍化危害的贡献较大。芦苇叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性随干旱及盐分加剧增加显著,两者对水分亏缺的响应较盐分敏感,且可有效缓解沙丘生境由于缺水所造成的氧化损伤,使丙二醛(MDA)含量维持在相对较低水平。过氧化物酶(POD)活性在沙丘和盐渍化生境内都比较高,对抵抗盐渍化和干旱起着同样重要的作用。     

Salinity and drought tolerance of mannitol-accumulating transgenic tobacco

Tobacco plants (Nicotiana tabacum L.) were transformed with a mannitol-1-phosphate dehydrogenase gene resulting in mannitol accumulation. Experiments were conducted to determine whether mannitol provides salt and/or drought stress protection through osmotic adjustment. Non-stressed transgenic plants were 20–25% smaller than non-stressed, non-transformed (wild-type) plants in both salinity and drought experiments. However, salt stress reduced dry weight in wild-type plants by 44%, but did not reduce the dry weight of transgenic plants. Transgenic plants adjusted osmotically by 0.57 MPa, whereas wild-type plants did not adjust osmotically in response to salt stress. Calculations of solute contribution to osmotic adjustment showed that mannitol contributed only 0-003-0-004 MPa to the 0.2 MPa difference in full turgor osmotic potential (π_o) between salt-stressed transgenic and wild-type plants. Assuming a cytoplasmic location for mannitol and that the cytoplasm constituted 5% of the total water volume, mannitol accounted for only 30–40% of the change in π_o of the cytoplasm. Inositol, a naturally occurring polyol in tobacco, accumulated in response to salt stress in both transgenic and wild-type plants, and was 3-fold more abundant than mannitol in transgenic plants. Drought stress reduced the leaf relative water content, leaf expansion, and dry weight of transgenic and wild-type plants. However, π_o was not significantly reduced by drought stress in transgenic or wild-type plants, despite an increase in non-structural carbohydrates and mannitol in droughted plants. We conclude that (1) mannitol was a relatively minor osmolyte in transgenic tobacco, but may have indirectly enhanced osmotic adjustment and salt tolerance; (2) inositol cannot substitute for mannitol in this role; (3) slower growth of the transgenic plants, and not the presence of mannitol per se, may have been the cause of greater salt tolerance, and (4) mannitol accumulation was enhanced by drought stress but did not affect π_o or drought tolerance.     

Effects of iso-osmotic NaCl and mannitol on growth, proline content, and antioxidant defense in Mammillaria gracilis Pfeiff. in vitro-grown cultures

Effects of iso-osmotic concentrations of NaCl and mannitol were studied in Mammilaria gracilis (Cactaceae) in both calli and tumors grown in vitro. In both tissues, relative growth rates were reduced under osmotic stress, which were accompanied by a decrease in both tissue water and K⁺ content. However, growth was inhibited to a lesser extent after exposure to NaCl, when accumulation of Na⁺ ions was observed. In calli, only salinity increased proline content, whereas with tumors proline accumulated after both osmotic stresses. Osmotic stresses also induced oxidative damage in both cactus tissues, although higher oxidative injury was caused by mannitol in calli and by salt in tumors. Low iso-osmotic concentrations of NaCl (75 mM) and mannitol (150 mM) increased peroxidase, ascorbate peroxidase, and esterase activities, whereas elevated catalase activity was recorded only after mannitol treatment in both tissues. High osmotic stress generally decreased enzymatic activities. However, in calli, esterase activity increased in response to high salinity, whereas ascorbate peroxidase activity was enhanced after high mannitol stress. In conclusion, both in vitro-grown cactus tissues were found to be sensitive to osmotic stress caused by either mannitol or NaCl, but accumulation of Na⁺ ions in response to salt somewhat contributed to osmotic adjustment. However, more prominent oxidative damage induced by NaCl compared to mannitol in tumor could be related to ion toxicity. The mechanisms that mediate responses to salt- and mannitol-induced osmotic stresses differed and were dependent on tissue type.     

Application of silicon improves salt tolerance through ameliorating osmotic and ionic stresses in the seedling of Sorghum bicolor

Silicon has been widely reported to have a beneficial effect on improving plant tolerance to biotic and abiotic stresses. However, the mechanisms of silicon in mediating stress responses are still poorly understood. Sorghum is classified as a silicon accumulator and is relatively sensitive to salt stress. In this study, we investigated the short-term application of silicon on growth, osmotic adjustment and ion accumulation in sorghum (Sorghum bicolor L. Moench) under salt stress. The application of silicon alone had no effects upon sorghum growth, while it partly reversed the salt-induced reduction in plant growth and photosynthesis. Meanwhile, the osmotic potential was lower and the turgor pressure was higher than that without silicon application under salt stress. The osmolytes, the sucrose and fructose levels, but not the proline, were significantly increased, as well as Na⁺ concentration was decreased in silicon-treated plants under salt stress. These results suggest that the beneficial effects of silicon on improving salt tolerance under short-term treatment are attributed to the alleviating of salt-induced osmotic stress and as well as ionic stress simultaneously.     

Ionic and Water Relations Responses of Two Populations of a Non-Halophyte to Salinity

Bowman, W. D. 1988. Ionic and water relations responses of twopopulations of a non-halophyte to salinity.–J. exp. Bot39: 97–105 Salinity-induced changes in the ionic and water relations inplants from two naturally-occurring populations of the C₄ non-halophyteAndropogon glomeratus were measured to detect differences inthe capacity to adjust osmotic potentials and in ion contentpotentially responsible for the osmotic adjustment Pressure-volumecurves and leaf ion content were measured in plants from twopopulations, salt marsh and inland, after long-term exposureto three salinity levels. Osmotic adjustment and decreases inthe bulk tissue elasticity occurred to a similar extent in bothpopulations with increasing salinity. Cl^– concentrationsincreased with increasing salinity in both populations, whereasleaf Na⁺ concentrations increased only in the inland population,but were higher at all salinities in the marsh population. K⁺concentrations changed little with increasing salinity. Prolineconcentrations increased only at the highest salinity level,and did not difler significantly between populations. Theseresults suggest a role for Na⁺ uptake and regulation in osmoticadjustment in the marsh population, contrasting with studiesof salt tolerance in other nonhalophytic grasses     

Growth, water content, and solute accumulation of two tobacco cell lines cultured on sodium chloride, dextran, and polyethylene glycol

Simulated drought tolerance was compared for an NaCl-adapted and a nonadapted cell line of tobacco (Nicotiana tabacum var. Samsum) to determine the relationship of salt and drought tolerances. The osmotic adjustment and growth of these two lines was followed when cultured on solid media which contained isosmotic concentrations of NaCl, KCl, polyethylene glycol (PEG) or dextran. One line was adapted to growth on 130 millimolar NaCl, but the other was not.     

Fast growth responses of barley and durum wheat plants to NaCl- and PEG-treatment: resolving the relative contributions of water deficiency and ion toxicity

Effects of adding osmotically comparable concentrations of PEG and NaCl to nutrient solution were studied in 1-week-old durum wheat (Triticum durum Desf., salt-sensitive) and barley (Hordeum vulgare L., more salt tolerant). Both treatments arrested leaf extension immediately, followed by partial recovery within 40–60 min. Similarities and differences were observed between the responses of the two species and between the two treatments. Typically, PEG-treatment increased leaf extensibility of both barley and wheat as measured by changes in leaf extension rate monitored by an electromechanical sensor to which a stretching counter-weight was added. In barley, NaCl-treatment increased extensibility in a similar way to PEG, but in wheat, extensibility did not change within 40 min of NaCl-treatment. The contrasting fast responses of wheat plants to NaCl and PEG treatments suggests that, unlike barley, wheat leaf extension was sensitive not only to osmotic effects of salinity, but also to ion toxicity. Thus, separate PEG- and NaCl-treatments enabled us to distinguish between ionic and osmotic effects and to show, for the first time, that ionic effects of salinity on leaf extension can commence after only short-term exposure (<1 h) in the case of a salt-sensitive species such as durum wheat.