渗透胁迫对山黧豆幼苗H2O2及毒素积累的影响

用PEG经根部处理15d龄的山黧豆幼苗,取幼苗叶片为实验材料,测定过氧化氢酶（CAT）、过氧化物酶（POD）活性、过氧化氢（H2O2）和毒素（β-N-oxalyl-α,β-diaminopropionic acid,ODAP）的含量。结果表明,随着PEG处理时间的延长,POD和CAT活性降低,而H2O2和ODAP含量显著升高;在PEG处理液中加入二乙基二硫代氨基甲酸钠(diethyldithiocarbamate,DDC)和氨基三唑(aminotriazole,AT)后分别抑制和促进H2O2的产生,DDC可降低叶片中ODAP的含量,AT则使ODAP积累。由此我们推测,水分胁迫条件下活性氧代谢与ODAP的积累有关。     

渗透胁迫对山黧豆幼苗H_2O_2及毒素积累的影响

用PEG经根部处理 15d龄的山黧豆幼苗 ,取幼苗叶片为实验材料 ,测定过氧化氢酶 (CAT)、过氧化物酶 (POD)活性、过氧化氢 (H2 O2 )和毒素 ( β N oxalyl α ,β diaminopropionicacid ,ODAP)的含量。结果表明 ,随着PEG处理时间的延长 ,POD和CAT活性降低 ,而H2 O2 和ODAP含量显著升高 ;在PEG处理液中加入二乙基二硫代氨基甲酸钠 (diethyldithiocarbamate ,DDC)和氨基三唑 (aminotriazole ,AT)后分别抑制和促进H2 O2 的产生 ,DDC可降低叶片中ODAP的含量 ,AT则使ODAP积累。由此我们推测 ,水分胁迫条件下活性氧代谢与ODAP的积累有关     

山黧豆根系对H2O2诱导氧化胁迫的生理应答

以水培7d苗龄的山黧豆幼苗为材料,向水培溶液中施加不同浓度H2O2处理山黧豆幼苗24h,分析山黧豆根系受氧化胁迫的程度与抗氧化系统的应答特征,以揭示山黧豆对氧化胁迫的耐受机制。结果显示:(1)随外源H2O2处理浓度的不断增加,山黧豆幼苗侧根的数目无显著变化,而其根的鲜重则显著降低。(2)同时,根系组织的内源H2O2染色范围和程度显著增高,但根尖区域始终保持较低水平的H2O2;相反,O-·2染色范围和程度明显减少,根尖区域却始终保持较高水平的O-·2。(3)同期根系抗坏血酸(ASC)含量及过氧化氢酶(CAT)、过氧化物酶(POD)与抗坏血酸过氧化物酶(APX)的活性均表现出了先升高后降低的趋势,而超氧化物歧化酶(SOD)一直表现为持续上升的趋势。研究表明,在外源H2O2胁迫条件下,山黧豆根系O-·2的积累可能与其生长和活力呈正相关,而根系H2O2的积累则与其受氧化胁迫程度呈正相关;低浓度的H2O2处理可以提高山黧豆抗氧化系统对体内活性氧的清除能力。     

山黧豆幼苗对干旱胁迫的生理响应

用PEG6000模拟干旱对山黧豆进行胁迫。结果发现,胁迫初期（0~48 h）,突然的水分亏缺使气孔导度（Sc）和蒸腾速率（Tr）迅速下降,而净光合速率（Pn）和水分有效利用率（WUE）基本维持稳定。胁迫后期（48~108 h）,上述四个光合指标均不同程度地向对照水平恢复;脯氨酸和相对电导率（REC）受胁迫强度影响较小,但与胁迫时间呈明显正相关,分别在48和60 h增幅最大,而且当REC上升至对照的50%左右时,脯氨酸含量已达对照的14倍之多。由此认为,山黧豆可能主要通过迅速减小Sc和Tr以及大量而急剧的积累脯氨酸来减轻干旱所造成的伤害。     

安徽山黧豆的核型

山黧豆属(又名香豌豆属)(Lathyrus Linn.)全世界共约140种,已做过染色体计数者72种。我国约16种,大部分产西南、西北和东北各省区。近年来皖南农学院朱玉简等同志在安徽宣城发现一新种,命名为安徽山黧豆(Lathyrus anhuiensis Y.J.Zhu et R.X.Meng)。鉴于该新种分布区非常局限,个体数也不多,为了及时掌握其细胞学情况,特通过该院叶如欣同志取得部分种子进行了染色体的计数和核型的描述。     

山黧豆毒素ODAP的生物合成及与抗逆性关系研究进展

有关山黧豆毒素ODAP的生物合成途径的前体物和合成程序已经证实,但其关键合成酶尚未分离与鉴定,因而无法克隆相应基因和利用反义RNA技术以控制其生物合成。研究表明,利用相应的抑制剂控制ODAP生物合成前体物可降低ODAP的积累量。山黧豆中ODAP含量与其抗逆性之间密切相关,这与其能有效地清除山黧豆中·OH自由基有关,外源ODAP处理获同样效果。此外,因ODAP既是含氮化合物,又是游离氨基酸,极易溶于水,可在逆境胁迫下与脯氨酸和多胺一样大量而迅速地积累,推测它也可能作为细胞渗透调节物质和防脱水剂,并在氮代谢和能量代谢方面起重要作用。对今后该领域的重点研究方向也进行了探讨。     

山黧豆抗逆性研究进展

山黧豆是一种栽培历史悠久、种植广泛的豆科作物,具有很高的蛋白质含量和极强的耐旱能力,因而成为一些干旱、贫困和人口众多地区的主要饲料和粮食作物,且被考虑作为可持续发展农业的模式作物。随着人类对粮食、蛋白质和新型食物资源需求的日益增长,山黧豆的研究引起了世界各国学者的重视。该文对国内外近年来有关山黧豆在干旱、盐、重金属及生物胁迫下抗逆性方面的研究进展作了概述,同时简要介绍了山黧豆与干旱相适应的形态特征,并对亟需重点研究的几个方向作了展望。     

山黧豆毒素的薄层分离

通过对山黧豆中常见的20几种游离氨基酸薄层层析发现,其毒素ODAP的Rf值与好几种相关氨基酸的接近,而用阳离子交换柱对氨基酸抽提样进行简单的分离纯化,第一个洗脱出来的即为ODAP,这样在排除其它氨基酸干扰的情况下再进行ODAP的薄层分析将得到准确的结果。     

胁迫处理对林生山黧豆蛋白质多肽及其含量的影响

应用二维电泳技术,分析了经水分胁迫（ＰＥＧ）、盐分胁迫（ＮａＣｌ）和热激（４０℃）处理后林生山黧豆（ＬａｔｈｙｒｕｓｓｙｌｖｅｓｔｒｉｓＬ．）体内蛋白质多肽及其含量的变化。有些蛋白质经ＰＥＧ、ＮａＣｌ和热激处理后可以产生相同的变化。两种不同的胁迫因子对某些蛋白质的影响有一定的共同性。特定的胁迫条件可以造成特定的影响。不同胁迫因子对同一蛋白质多肽可以造成不同的影响。胁迫下蛋白质的变化可能与林生山黧豆抵抗和适应胁迫条件的能力以及体内非蛋白质氨基酸的代谢有关     

水分胁迫下山黧豆中ABA及ODAP的积累研究

用PEG、PEG+ABA、ABA分别处理15d龄的山黧豆幼苗,取其叶片为实验材料,测定内源ABA、ODAP、MDA和H₂O₂含量以及几种抗氧化酶活性,结果表明,与对照相比处理材料叶片中ABA和ODAP含量显著增加;外源ABA的加入降低了PEG胁迫引起的MDA和H₂O₂含量的增加,延缓了PEG胁迫引起的CAT活性的衰减,提高了GR活性.用外源ABA长时间处理山黧豆,发现叶片中ABA含量显著增加,随后出现ODAP的积累;ABA处理初期(0～3d)对叶片中活性氧代谢影响不大,随着ABA处理时间的延长(7～15d),可引起叶片中SOD、POD、CAT、GR活性的降低,MDA、H₂O₂含量的增加,表明ABA确实可促进ODAP的积累.     

渗透胁迫对高粱根中K~+累积的刺激作用

本工作中发现,2,4—二硝基酚(DNP)可有效地洗去高粱根中的K~+,从而提高了测定和比较K~+累积量的显示度和准确性,渗透胁迫下,高粱根中K~+的累积量比对照增加高达6.7倍;同时,组织的H~+分泌明显受到促进,动力学研究表明,经PEG胁迫的高粱根对K~+的亲和力显著增强。对照:K_m=9.25mmol/L,V_m=23.6μmolg~(-1)DW min~(-1);PEG处理者:K_m=27.25μmol/L,V_m=14.71μmolg~(-1)DW min~(-1).地上部的存在有利于 K~+的吸收。渗透胁迫所促进的K~+吸收可被亚胺环己酮(CHM)完全抑制,这一结果暗示渗透胁迫诱导的K~+吸收的增加依赖于蛋白质的诱导合成,本文讨论了K~+吸收增强的可能机理。     

盐度胁迫下缢蛏渗透压变化及V-ATPase H基因的表达分析

为研究V-ATPaseH基因在缢蛏(Sinonovaculaconstricta)盐度胁迫中的功能,以缢蛏成体为实验材料,将缢蛏置于5、15、20、25、35盐度水体中进行胁迫实验,测定了不同胁迫时间缢蛏的血清渗透压、V-ATPase活性变化,克隆了V-ATPase H基因的开放阅读框(ORF)全长序列,并分析其m RNA表达特征。结果显示,低盐组(盐度5和盐度15)和高盐组(盐度25和盐度35)缢蛏血清渗透压变化明显,与对照组(盐度20)有极显著差异(P <0.01)。随着时间的推移,实验组V-ATPase活力整体呈现先下降后上升的趋势,对照组(盐度20)无明显变化。V-ATPase H基因开放阅读框长度1 440 bp,编码479个氨基酸。q PCR结果显示,V-ATPase H基因在缢蛏鳃中的表达量极显著高于水管、外套膜、肾、肝胰腺、唇瓣、足6个组织(P <0.01);盐度胁迫下各个实验组V-ATPase H基因在鳃中的表达量持续上升,在24 h达到峰值,显著高于对照组(P <0.05)。实验结果表明,缢蛏V-ATPase H基因在盐度适应过程中主要在低盐和高盐...     

渗透胁迫对小麦幼苗根系呼吸的影响

用PEG—6000调节培养液的渗透势,研究了渗透胁迫对小麦幼苗根系呼吸作用的影响。在-0.5 MPa的溶液中根总呼吸强度显著降低,不同苗龄根的反应差异明显;随胁迫加强呼吸强度随之降低;根系ATP含量减少。在胁迫初期呼吸废物对呼吸强度的降低无补偿作用,而在后期(72 h后)则可提高呼吸强度。 中度水分胁迫下,HMP支路活性上升,EMP-TCAO途径活性降低;抗氰呼吸活性增大,而对氰敏感的系统活性减低;细胞色素氧化酶活性显著低于对照。     

Preferential Osmolyte Accumulation: a Mechanism of Osmotic Stress Adaptation in Diazotrophic Bacteria

A common cellular mechanism of osmotic-stress adaptation is the intracellular accumulation of organic solutes (osmolytes). We investigated the mechanism of osmotic adaptation in the diazotrophic bacteria Azotobacter chroococcum, Azospirillum brasilense, and Klebsiella pneumoniae, which are adversely affected by high osmotic strength (i.e., soil salinity and/or drought). We used natural-abundance ¹³C nuclear magnetic resonance spectroscopy to identify all the osmolytes accumulating in these strains during osmotic stress generated by 0.5 M NaCl. Evidence is presented for the accumulation of trehalose and glutamate in Azotobacter chroococcum ZSM4, proline and glutamate in Azospirillum brasilense SHS6, and trehalose and proline in K. pneumoniae. Glycine betaine was accumulated in all strains grown in culture media containing yeast extract as the sole nitrogen source. Alternative nitrogen sources (e.g., NH₄Cl or casamino acids) in the culture medium did not result in measurable glycine betaine accumulation. We suggest that the mechanism of osmotic adaptation in these organisms entails the accumulation of osmolytes in hyperosmotically stressed cells resulting from either enhanced uptake from the medium (of glycine betaine, proline, and glutamate) or increased net biosynthesis (of trehalose, proline, and glutamate) or both. The preferred osmolyte in Azotobacter chroococcum ZSM4 shifted from glutamate to trehalose as a consequence of a prolonged osmotic stress. Also, the dominant osmolyte in Azospirillum brasilense SHS6 shifted from glutamate to proline accumulation as the osmotic strength of the medium increased.     

Accumulation of Trehalose as a Compatible Solute under Osmotic Stress in Euglena gracilis Z

ABSTRACT. The photosynthetic protozoon Euglena gracilis, accumulated a large amount of trehalose in the cells under salt or osmotic stresses. Radioactivity of [14C] paramylon, a β-1,3-polyglucan which was stored in the cells of E. gracilis. was degraded rapidly and this radioactivity was almost stoichiometrically incorporated into trehalose. The interconversion of trehalose from paramylon by salt or osmotic stresses was dependent on the concentrations or osmotic pressures, suggesting that E. gracilis accumulate trehalose as an osmoprotectant. After the removal of salt or osmotic stresses, trehalose was gradually degraded, however, it was not converted into paramylon.     

Effects of Extended Periods of Osmotic Stress on Water Relationships of Pepper

Pepper plants grown to uniform size in a controlled environment were subjected to an osmotic stress for periods of 1 to 10 days. Polyethylene glycol 400 was used as the osmotic agent. Leaf area of the plants, grown under uniform conditions, was proportional to the weight of the plants. This relationship was not altered by reduction in rate of growth due to a decrease in osmotic potential of the nutrient solution. The rate of transpiration of the pepper plants decreased as the osmotic potential of the nutrient solution was decreased. The reduction in rate of transpiration was most rapid when the osmotic potential was reduced from ?0.5 to ?7.5 bars. There was continued reduction in the rate of transpiration with change in potential to ?12.5 bar but this change was less than that at the higher potentials. The rate of transpiration remained at a reduced rate for as long as the plants were growing in the solution with low osmotic potential. Alternating the osmotic potential of the nutrient solution between ?0.5 and ?5.0 bar did not change the response to the ?5.0 tension. The reduction in rate of transpiration resulting from the lowering of the osmotic potential by addition of NaCl was similar to that produced by addition of polyethylene glycol. Water potential, osmotic potential, relative water content and stomatal movement were all in dynamic equilibrium with the water content of the leaves. The water content of the leaves was regulated by the supply and demand. In these investigations the demand remained constant. The supply was altered by decreasing the difference in water potential between leaf and substrate and by an increase in resistance to flow of water in the roots as a result of the decrease in osmotic potential of the nutrient solution.     

渗透胁迫和缺磷对小麦幼苗生长的影响

水培条件下缺磷小麦幼苗的叶片含水量和叶绿素含量显著降低,丙二醛含量增加,小麦幼苗生长受抑,地上部分生长受到的影响大于根系,上述指标的变化幅度还与缺磷程度呈正相关,且不耐低磷品种中国春大于耐低磷品种烟中144。在相同条件下,渗透胁迫和缺磷两者表现出胁迫加剧的现象。     

渗透胁迫和外源脱落酸对梭梭幼苗生理特性的影响

水分、渗透胁迫和外源脱落酸（ＡＢＡ）对旱生植物梭梭幼苗的某些生理特性存在显著影响。梭梭幼苗有很强的吸水能力,渗透胁迫下脯氨酸含量增加,其细胞膜相对透性对渗透胁迫不敏感,在脱水过程中具有较强的持水能力,外源ＡＢＡ加强了梭梭幼苗的抗渗透胁迫和抗脱水的能力。