盐碱混合生态条件的人工模拟及其对羊草胁迫作用因素分析

将中性盐NaCl和Na2SO4,碱性盐NaHCO3和Ｎa2CO3按不同比例混合,模拟出３０种盐度和pH各不相同的盐碱生态条件,并对羊草苗进行盐碱混合胁迫处理,测定其日相对生长率（ＲＧＲ）等７项胁变指标,用数学方法分析盐度,缓冲量等各种胁迫因素与诸项胁变指标间的相互关系,结果表明：30种处理均匀覆盖了总盐度50-350mmol/L,pH7.14-10.81范围内的各种盐碱条件,用盐度,缓冲量,pH和[Cl^-]即可代表盐碱混合胁迫的所有胁迫作用因素,诸胁变指标与这4因素间均具有高度线性相关性,4因素对胁变的贡献明显不同,其中缓冲量和盐度是决定性的主导因素,pH和[Cl^-]的作用明显次之,有时甚至可以忽略,不同胁变指标与各因素的关系也有不同。分析结果表明,对于盐碱混合胁迫来说,以盐度加缓冲量代表总胁强较为合理。     

Chlorophyllase Activity and Chlorophyll Content in Wild Type and eti 5 Mutant of Arabidopsis thaliana Subjected to Low and High Temperatures

Chlorophyll a (Chl a) content and chlorophyllase (Chlase) activity from leaves of wild type (WT) and the ethylene-insensitive mutant (eti 5) of Arabidopsis thaliana (L.) Heynh during temperature stress and plant recovery have been studied. The plants were subjected to temperatures of 4 °C (LT) and 38 °C (HT) for 24 h. Chl a gradually decreased somewhat during stress and in the first day of recovery, especially in HT-treated plants. At the end of the experimental period (1 d stress and 10 d recovery) Chl a content was lower in eti 5 plants than in WT ones. The Chlase in WT was more affected than in eti 5 plants during the temperature treatment and the recovery period. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparative physiology of salt and water stress

Plant responses to salt and water stress have much in common. Salinity reduces the ability of plants to take up water, and this quickly causes reductions in growth rate, along with a suite of metabolic changes identical to those caused by water stress. The initial reduction in shoot growth is probably due to hormonal signals generated by the roots. There may be salt-specific effects that later have an impact on growth; if excessive amounts of salt enter the plant, salt will eventually rise to toxic levels in the older transpiring leaves, causing premature senescence, and reduce the photosynthetic leaf area of the plant to a level that cannot sustain growth. These effects take time to develop. Salt-tolerant plants differ from salt-sensitive ones in having a low rate of Na+ and Cl-- transport to leaves, and the ability to compartmentalize these ions in vacuoles to prevent their build-up in cytoplasm or cell walls and thus avoid salt toxicity. In order to understand the processes that give rise to tolerance of salt, as distinct from tolerance of osmotic stress, and to identify genes that control the transport of salt across membranes, it is important to avoid treatments that induce cell plasmolysis, and to design experiments that distinguish between tolerance of salt and tolerance of water stress.     

The inhibition of photosynthesis and photorespiration in isolated mesophyll cells of Phaseolus and Lycopersicon by reduced osmotic potentials

Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by ¹⁴CO₂ release in CO₂-free air and by ¹⁴CO₂ release from the oxidation of [1–¹⁴C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO₂ compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I⁻¹1 at −1.08 MPa to 130 μl 1⁻¹ for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non- stomatal inhibition of CO₂ assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure.     

A cytosolic class I small heat shock protein, RcHSP17.8, of Rosa chinensis confers resistance to a variety of stresses to Escherichia coli, yeast and Arabidopsis thaliana

Among the heat shock proteins (HSPs) of higher plants, those belonging to the small HSP (sHSP) family remain the least characterized in functional terms. To improve our understanding of sHSPs, we have characterized RcHSP17.8 from Rosa chinensis . Sequence alignments and phylogenetic analysis reveal this to be a cytosolic class I sHSP. RcHSP17.8 expression in R. chinensis was induced by heat, cold, salt, drought, osmotic and oxidative stresses. Recombinant RcHSP17.8 was overexpressed in Escherichia coli and yeast to study its possible function under stress conditions. The recombinant E. coli and yeast cells that accumulated RcHSP17.8 showed improved viability under thermal, salt and oxidative stress conditions compared with control cultures. We also produced transgenic Arabidopsis thaliana that constitutively expressed RcHSP17.8. These plants exhibited increased tolerance to heat, salt, osmotic and drought stresses. These results suggest that R. chinensis cytosolic class I sHSP (RcHSP17.8) has the ability to confer stress resistance not only to E. coli and yeast but also to plants grown under a wide variety of unfavorable environmental conditions.     

盐碱协同胁迫对向日葵抗氧化酶系统的影响

根据中国东北盐碱土壤特点,将4种盐NaCl、NaHCO3、Na2SO4和Na2CO3按不同比例混合,模拟出25种盐度和pH值各不相同的复杂盐碱条件(盐浓度为50～250 mmol/L,pH值为712～1046),并对向日葵苗进行盐碱混合胁迫处理,研究了向日葵超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)酶等抗氧化酶系统和丙二醛(MDA)的盐碱协同胁迫效应．结果表明, 向日葵抗氧化物酶活性强弱同时与盐度和碱度密切相关,3种抗氧化物酶活性对于盐浓度的反应相似,均为其含量随着盐浓度的升高开始逐渐升高然后下降,而对于pH的影响,不同酶反应结果不同．即随着pH值升高,SOD酶活性和CAT酶活性降低,而POD酶活性反应则是随着pH值升高活性也升高．双向方差分析(ANOVA)结果表明：盐碱效应对于3种酶活力的影响是显著的．其中,盐效应对POD和SOD活性的影响比pH值的影响大,而pH值对CAT活性的影响效应比盐效应大．除SOD外,盐碱效应的交互作用显著 (P<0001)．抗氧化酶系统和MDA含量两者间相关性和逐步回归分析表明,3种酶对MDA的影响效应随其强度不同呈现显著不同．其中SOD是1个主导因子,CAT 处于次位, 而POD的影响不大,甚至可以忽略．     

三种冬青属树种的耐涝性和耐旱性评价

通过致死性干旱和致死性水涝处理,用生理生态方法,对冬青(Ilexchinensis)、绿冬青(I.viridis)和无刺枸骨(I.cornatavar.fortunei)进行抗逆性研究。耐涝性结果表明随淹水时间延长,3种受淹冬青体内的游离脯氨酸和丙二醛含量增加,净光合速率下降;比较而言,绿冬青上述受淹反应出现早,无刺枸骨出现迟,而冬青介于二者之间;绿冬青耐涝约1周,无刺枸骨耐涝2周以上,冬青耐涝介于二者之间,在江南水乡推广利用,耐涝方面不会成为限制因素。耐旱结果表明随干旱的逐渐加重,3种冬青体内的游离脯氨酸含量呈上升趋势,比较而言,绿冬青上升的峰值出现早,冬青和无刺枸骨的上升峰值出现迟;绿冬青耐旱约15d,无刺枸骨耐旱约25d,冬青介于二者之间。3种冬青均有一定的抗逆性,其中无刺枸骨对水胁迫的适应能力最强,冬青次之,而绿冬青相对较弱。     

植物小RNAs及其抗胁迫机制研究进展

植物非编码小RNA(sRNAs)主要分为三类:微小RNA(m iRNAs)、小干扰RNA(siRNAs)和长小片段干扰RNA(lsiRNAs)。三者的生物合成和作用机制有所不同,但他们主要都通过介导靶mRNAs的剪切或抑制其翻译来调控基因的表达。这篇文章主要介绍小RNA研究的最新进展,并重点阐述其在非生物和生物胁迫中发挥的作用,如应对矿质元素缺乏、氧化胁迫、ABA胁迫以及病原菌入侵等生理过程。     

Occurrence and changes of proline content in plants in the southern Namib Desert in relations to increasing and decreasing drought

Over a period of seven years (1977–1983) the proline content and its responses to climatic changes were investigated in plants — especially Mesembryanthemaceae — in the southern Namib Desert (South Africa). Among 95 species in 26 families, 61 had detectable amounts of proline. In several of these species the proline content increased considerably in years with insufficient rainfall but decreased when the rainfall was abundant again. When individuals of the same species were grown at different sites, water availability in the soil determined their proline content. Many of the investigated species showed a clear diurnal fluctuation in their proline content with a remarkable proline accumulation during times of highest evaporative demand. In general, the higher the proline content the more pronounced were the changes, indicating that in these species-predominantly annual plants — proline was most probably involved in drought tolerance. The observation that proline accumulation and degradation reacted sensitively to changing climatic conditions over many years confirmed the correlation of proline synthesis to increasing water stress as postulated by the results of laboratory experiments with Mesembryanthemaceae.Abbreviations CAM Crassulacean acid metabolism - DW dry weight - WC water content Dedicated to Professor Dr. Hubert Ziegler on the occassion of his 60th birthday     

干旱胁迫对发菜超微结构及抗性生理的影响

发菜是一种陆生固氮蓝藻,具有强烈的旱生生态适应性。对干旱胁迫条件下发菜超微结构和抗性生理进行了研究。结果表明：随着干旱胁迫加重,发菜细胞大小和细胞壁厚度变化不显著,胶质鞘趋于紧密,类囊体排列趋于紊乱,多角体变得模糊不清甚至消失,糖原颗粒数目减少,但结构颗粒数目没有明显变化。随着干旱胁迫的加重,发菜SOD、CAT活性呈先升高再下降趋势,SOD在含水量为120%时达到高峰;CAT活性在含水量为445%时达到高峰;MDA,氧自由基随着干旱胁迫加重,其含量呈上升趋势;H₂O₂含量随干旱胁迫加重呈先升高再下降趋势,在含水量为120%时达到峰值。干燥储存1年的发菜与恢复活性的发菜有明显差异性,其SOD、CAT活性较低、MDA、H₂O₂含量较少,但是氧自由基含量最高。研究结果对深入研究发菜的耐旱机理奠定了基础。     

Expression of the 1-SST and 1-FFT genes and consequent fructan accumulation in Agave tequilana and A. inaequidens is differentially induced by diverse (a)biotic-stress related elicitors

The expression of genes coding for sucrose:sucrose 1-fructosyltransferase (1-SST; EC 2.4.1.99) and fructan:fructan 1-fructosyltransferase (1-FFT; EC 2.4.1.100), both fructan biosynthesizing enzymes, characterization by TLC and HPAEC-PAD, as well as the quantification of the fructo-oligosaccharides (FOS) accumulating in response to the exogenous application of sucrose, kinetin (cytokinin) or other plant hormones associated with (a)biotic stress responses were determined in two Agave species grown in vitro, domesticated Agave tequilana var. azul and wild A. inaequidens. It was found that elicitors such as salicylic acid (SA), and jasmonic acid methyl ester (MeJA) had the strongest effect on fructo-oligosaccharide (FOS) accumulation. The exogenous application of 1 mM SA induced a 36-fold accumulation of FOS of various degrees of polymerization (DP) in stems of A. tequilana. Other treatments, such as 50 mM abscisic acid (ABA), 8% Sucrose (Suc), and 1.0 mg L⁻¹ kinetin (KIN) also led to a significant accumulation of low and high DP FOS in this species. Conversely, treatment with 200 μM MeJA, which was toxic to A. tequilana, induced an 85-fold accumulation of FOS in the stems of A. inaequidens. Significant FOS accumulation in this species also occurred in response to treatments with 1 mM SA, 8% Suc, and 10% polyethylene glycol (PEG). Maximum yields of 13.6 and 8.9 mg FOS per g FW were obtained in stems of A. tequilana and A. inaequidens, respectively. FOS accumulation in the above treatments was tightly associated with increased expression levels of either the 1-FFT or the 1-SST gene in tissues of both Agave species.     

Cytokinin action in response to abiotic and biotic stresses in plants

The phytohormone cytokinin was originally discovered as a regulator of cell division. Later, it was described to be involved in regulating numerous processes in plant growth and development including meristem activity, tissue patterning, and organ size. More recently, diverse functions for cytokinin in the response to abiotic and biotic stresses have been reported. Cytokinin is required for the defence against high light stress and to protect plants from a novel type of abiotic stress caused by an altered photoperiod. Additionally, cytokinin has a role in the response to temperature, drought, osmotic, salt, and nutrient stress. Similarly, the full response to certain plant pathogens and herbivores requires a functional cytokinin signalling pathway. Conversely, different types of stress impact cytokinin homeostasis. The diverse functions of cytokinin in responses to stress and crosstalk with other hormones are described. Its emerging roles as a priming agent and as a regulator of growth‐defence trade‐offs are discussed.     

干旱和盐胁迫对马铃薯试管苗亚细胞结构及生理生化指标的影响

以‘陇薯3号’脱毒试管苗为材料,研究了不同浓度PEG-4000(0、2%、4%、6%、8%)和NaCl(0、25、50、100、200mmol/L)对马铃薯2周大小试管苗根系生长、叶肉细胞超微结构及部分生理生化指标的影响,为筛选耐盐抗旱马铃薯种质提供理论依据。结果显示:(1)随着PEG-4000和NaCl浓度的增加,马铃薯试管苗根总长、根体积、根数均呈现下降趋势,并且胁迫浓度越高时间越长其下降趋势越明显,而盐胁迫处理的下降幅度明显大于PEG胁迫处理。(2)随着PEG-4000和NaCl浓度的增加,马铃薯试管苗叶肉细胞细胞壁明显变厚,发生明显的质壁分离,嗜锇颗粒显著增加,出现大量囊泡,叶绿体损害逐渐加剧,直至完全解体。(3)随着PEG-4000和NaCl浓度的增加,马铃薯试管苗脯氨酸(Pro)含量显著增加,过氧化氢(CAT)和超氧化物歧化酶(SOD)活性显著增强,而其丙二醛(MDA)含量迅速增加,但叶片叶绿素含量持续下降。研究表明,在PEG-4000模拟干旱和NaCl胁迫条件下,马铃薯试管苗叶片叶绿体结构受到严重损害,叶绿素含量显著降低,且胁迫程度越强损害越严重、下降幅度越大;同时,干旱和高盐胁迫也诱导马铃薯试管苗脯氨酸含量和抗氧化酶CAT和SOD活性显著上调,一定程度上缓解了干旱和高盐胁迫的伤害。     

Effects of acoustic and immobilization stress on background impulse activity of neurons of the central and lateral nuclei of the Amygdala

It was shown that acoustic and immobilization stresses (developed due to a 2.5-h-long session of intensive, 100 dB, acoustic influence and a 2-h-long session of soft fixation of the body and extremities, respectively) result in significant modifications of the characteristics of background impulse activity of neurons of the nuclei of the rat amygdalar complex. Modifications were greater in the lateral nucleus of the amygdala. Possible roles of some structures of the monoaminergic cerebral systems in acute stress-related transformations of the impulse activity generated by neurons of the amygdalar complex are discussed. Neirofiziologiya/Neurophysiology, Vol. 38, No. 2, pp. 131–139, March–April, 2006.     

Variability of salivary markers of oxidative stress and antioxidant status in young healthy individuals

Objectives: Salivary advanced glycation end-products (AGEs), advanced oxidation protein products (AOPP), total antioxidant capacity (TAC), and ferric reducing ability of saliva (FRAS) are increased in various diseases. Little data exist for these markers in the healthy population. The aim of this study was to assess the inter-individual and intra-individual variability of AGEs, AOPP, TAC, and FRAS in the saliva of young healthy individuals.

Methods: Unstimulated saliva samples were collected from 16 females and 18 males daily over a period of 30 days. Markers were measured using spectrophotometric and spectrofluorometric microplate-based methods.

Results: All salivary markers measured were significantly higher in men than in women (P?<?0.05 for AGEs; P?<?0.001 for AOPP, TAC, and FRAS). The inter-individual variability was approximately 60% for AGEs and AOPP and 30–40% for TAC and FRAS in both genders. The inter-individual variability of FRAS was higher in men vs. women (P?<?0.01). Intra-individual variability ranged from 20% for TAC, to 30% for AGES and FRAS and 45% for AOPP.

Discussion: Intra-individual variability of salivary AGEs, AOPP, TAC, and FRAS indicates that their use is currently limited to large cohort studies. Identifying the underlying factors related to the high inter-individual and intra-individual variability is needed. Sex differences should be considered in future studies.