盐胁迫对大麦叶片类囊体膜组成和功能的影响

盐胁迫下大麦叶片类囊体膜蛋白和叶绿素含量以及叶绿素ａ／叶绿素ｂ,磷脂／膜蛋白和膜脂结合半乳糖／膜蛋白比值下降,膜脂中亚麻酸摩尔百分数上长,不饱和指数上升,类囊体膜Ｈ＾＋－ＡＴＰａｓｅ活性先升后降,希尔反应一直呈较高活性。     

盐胁迫对大麦幼苗质膜,液泡膜上共价和非共价结合多胺含量的影响

用不同浓度ＮａＣｌ处理７ｄ龄大麦（Ｈｏｒｄｅｕｍ ｖｕｌｇａｒｅＬ．）幼苗３ｄ。以非共价键和共价键形式分别与质膜和液泡膜微囊及膜蛋白结合的多胺含量受低 度盐的促进而被高浓度盐所抑制。以非共价键形式与膜微囊结合的各种多胺中亚精胺（Ｓｐｄ）含量最高,占膜上多胺总量的４０％－７０％,与膜蛋白共价结合的各种多胺中腐胺（Ｐｕｔ）含量占主导地位,占膜蛋白上多胺总量的３５％－６０％。在根系液泡膜上发现一种含量丰     

盐胁迫对大麦叶片类囊体膜组成和功能的影响

盐胁迫下大麦叶片类囊体膜蛋白和叶绿素含量以及对绿素a／叶绿素b、磷脂／膜蛋白和膜脂结合半乳糖／膜蛋白的比值下降,膜脂中亚麻酸（18：3）摩尔百分数上升,不饱和指数上升,类囊体膜H －ATPase活性先升后降,希尔反应一直呈较高活性。类囊体膜组分和功能的变化可能与植物盐适应有关。     

大麦幼苗多胺合成比脯氨合成对盐胁迫更敏感

ＮａＣｌ２００ｍｍｏｌ／Ｌ处理结合＾１４Ｃ－Ｇｌｕ叶而饲喂６天龄大麦幼苗,结果证明盐胁迫下Ｐｒｏ主要积累在叶片中,在根系中ＰＡ的积累占优势。ＰＡ合成途径对盐胁迫的响应早于Ｐｒｏ。盐处理８ｈ以后ＰＡ与Ｐｒｏ的合成竞争共同前体Ａｒｇ。盐胁迫激活了Ｐｒｏ两条合成途径,胁迫８ｈ以前Ｐｒｏ积累主要受Ｇｌｕ途径控制,随后Ｏｒｎ途径对Ｐｒｏ积累的贡献占主导地位。盐胁迫促进了ＰＡ合成的Ａｒｇ途径,对Ｏｒｎ途径没有     

多胺浸种改善盐胁迫大麦根系液泡膜功能的机理

研究了0.1 mmol/L 腐胺 (Put) 和0.5 mmol/L 亚精胺 (Spd) 浸种对200 mmol/L NaCl胁迫下大麦(Hordeum vulgare L.)幼苗生长速率、干物质积累、离子分布、液泡膜蛋白结合多胺含量以及液泡膜膜脂组分与功能的影响.结果表明,Put和Spd浸种均可缓解盐胁迫对大麦幼苗的盐害,促进生长和干物质积累,降低大麦幼苗体内[Na+]/[K+].与盐处理的对照植株相比,Put和Spd浸种均可提高大麦幼苗根系液泡膜磷脂含量,降低糖脂结合半乳糖含量,而膜上非共价结合多胺含量Spd+PAx (一种未知多胺) 与 Put+Dap (二氨基丙烷)之比((Spd+PAx)/(Put+Dap))、共价和非共价结合多胺总量均上升.统计分析结果表明,液泡膜非共价结合多胺(Spd+PAx)/(Put+Dap)与H+-ATPase和H+-PPase活性呈显著正相关关系.     

多胺浸种改善盐胁迫大麦根系液泡膜功能的机理

研究了 0 .1mmol/L腐胺 (Put)和 0 .5mmol/L亚精胺 (Spd)浸种对 2 0 0mmol/LNaCl胁迫下大麦 (HordeumvulgareL .)幼苗生长速率、干物质积累、离子分布、液泡膜蛋白结合多胺含量以及液泡膜膜脂组分与功能的影响。结果表明 ,Put和Spd浸种均可缓解盐胁迫对大麦幼苗的盐害 ,促进生长和干物质积累 ,降低大麦幼苗体内 [Na ]/[K ]。与盐处理的对照植株相比 ,Put和Spd浸种均可提高大麦幼苗根系液泡膜磷脂含量 ,降低糖脂结合半乳糖含量 ,而膜上非共价结合多胺含量Spd PAx (一种未知多胺 )与Put Dap (二氨基丙烷 )之比 ( (Spd PAx) / (Put Dap) )、共价和非共价结合多胺总量均上升。统计分析结果表明 ,液泡膜非共价结合多胺 (Spd PAx) / (Put Dap)与H _ATPase和H _PPase活性呈显著正相关关系。     

大麦幼苗多胺合成比脯氨酸合成对盐胁迫更敏感

NaCl 2 0 0mmol/L处理结合14 C Glu叶面饲喂 6天龄大麦幼苗 ,结果证明盐胁迫下Pro主要积累在叶片中 ,在根系中PA的积累占优势。PA合成途径对盐胁迫的响应早于Pro。盐处理 8h以后PA与Pro的合成竞争共同前体Arg。盐胁迫激活了Pro两条合成途径 ,胁迫 8h以前Pro积累主要受Glu途径控制 ,随后Orn途径对Pro积累的贡献占主导地位。盐胁迫促进了PA合成的Arg途径 ,对Orn途径没有影响     

盐胁迫下大麦幼苗多胺的种类和状态与多胺氧化酶活性的关系

200 mmol/L的NaCl胁迫8 d大麦幼苗叶片和根系中的三种形态多胺都有不同程度地下降,其中游离态多胺含量的下降幅度最大;高氯酸不溶性结合态多胺含量变化较小.根系中PAO的活性先上升后下降,而叶片中PAO的活性先下降后上升.游离态多胺中,亚精胺和精胺(Spd Spm)的含量变化与相应部位PAO的活性变化趋势相反,表明PAO在盐胁迫下可能调节了游离态多胺的含量从而影响高氯酸可溶结合态与高氯酸不溶结合态多胺的含量.     

低温胁迫对类囊体膜脂代谢的影响

类囊体膜主要由膜脂、膜蛋白及一些光合色素等成分组成,它是植物进行光合作用的场所.低温能通过影响类囊体膜的结构而影响植物的光合作用.简述了类囊体膜的组成和功能,以及低温胁迫下类囊体膜脂及其脂肪酸组成的变化.简要介绍了膜脂与光抑制的关系,以及利用分子生物学手段研究三烯脂肪酸与植物抗冷性关系的相关进展.     

水分胁迫对玉米类囊体膜组分的影响

研究了水分胁迫对玉米（ZeamaysL,新玉4号）叶片类囊体膜的蛋白、色素组分,以及PSⅠ、PSⅡ和Cytb／f复合物的影响。类囊体膜蛋白电泳显示水分胁迫使总膜蛋白含量下降。高效液相色谱分析表明水分胁迫也引起类囊体膜色素成分的改变。通过测定P700及各种细胞色素的含量计算所得的PSⅠ、PSⅡ和Cytb／f复合物成分表明PSⅠ对水分胁迫不敏感,Cytb／f复合物在严重水分胁迫时才受到影响,而PSⅡ在中度和严重水分胁迫时均受到较明显的影响。     

New perspective on the mechanism of alleviating salt stress by spermidine in barley seedlings

Salt stress is considered to be a major limiting factor for plant growth and crop productivity. Salt injuries in plants are mostly due to excess Na⁺ entry. A possible survival strategy of plants under saline environments is the effective compartmentation of excess Na⁺ by sequestering Na⁺ in roots and inhibiting transport of Na⁺ from roots to shoots. Our previous study showed that exogenous application of polyamines (PAs) could attenuate salt injuries in barley plants. In order to further understand such protective roles of PAs against salt stress, the effects of spermidine (Spd) on sodium and potassium distribution in barley (Hordeum vulgare L.) seedlings under saline conditions were investigated. The results showed that exogenous application of Spd induced reductions in Na⁺ levels in roots and shoots with comparison of NaCl-treated plants, while no significant changes in K⁺ levels were observed. Correspondingly, the plants treated with Spd exogenously maintained high values of [K⁺]/[Na⁺] as compared with salt-stressed plants. Moreover, it was shown by X-ray microanalysis that K⁺ and Na⁺ accumulated mainly in the exodermal intercellular space and cortical cells of roots under salinity stress, and low accumulation was observed in endodermal cells and stelar parenchyma, indicating Casparian bands possibly act as ion transport barriers. Most importantly, Spd treatment further strengthened this barrier effects, leading to inhibition of Na⁺ transport into shoots. These results suggest that, by reinforcing barrier effects of Casparian bands, exogenous Spd inhibits Na⁺ transport from roots to shoots under conditions of high salinity which are beneficial for attenuating salt injuries in barley seedlings.     

Some morphological and anatomical observations during alleviation of salinity (NaCI) stress on seed germination and seedling growth of barley by polyamines

In this work, the effects of polyamine (cadaverine, putrescine, spermidine, spermine) pretreatments on the germination of barley seeds, seedling growth under saline (NaCI) conditions and on leaf anatomy of the seedlings grown for 20 days in pots with perlite containing different concentrations of NaCI prepared with Hoagland solutions following the germination period of 7 days were studied. The inhibitive effect of salt on seed germination and seedling growth was alleviated in varying degrees, and dramatically, by polyamine pretreatments at the levels of NaCI studied; particularly with lower levels of salt, the control seeds were able to germinate with great difficulty. Also, the successes of these pretreatments continued, even decreased, with higher levels of NaCI such that the control seeds showed no germination. On the other hand, on the various parameters of leaf anatomy of barley seedlings, interactions between pretreatments of polyamine and salinity, with some of these being statistically important, were observed.     

Polyamines and ”scavenging system”: influence of exogenous spermidine on Halliwell-Asada pathway enzyme activity in barley leaves under water deficit

Barley (Hordeum vulgare) seedlings were treated with spermidine before water stress to determine whether this polyamine influences the activity of Halliwell-Asada pathway enzymes. After the treatment, a decline in ascorbate peroxidase activity and an increase in glutathione reductase and monodehydroascorbate reductase activity were found. The latter effect was sustained throughout the period of experiments. The results suggest that the exogenous spermidine contributed to an improvement in the functioning of antioxidant Halliwell-Asada pathway enzymes and thereby to a reduction of the oxidative stress intensity under water deficit.     

Senescence-dependent degradation of Lhcb3 is mediated by a thylakoid membrane-bound protease

A novel proteolytic activity integrally associated with barley thylakoid membranes has been discovered and characterized. This enzymatic activity mediates senescence-dependent degradation of Lhcb3, one of the apoproteins of the major light-harvesting chlorophyll a/b protein complex of photosystem II. Once senescence of barley leaves is initiated by detachment and dark incubation, the degradation of Lhcb3 can proceed and be followed in vitro in an experimental system composed of thylakoids isolated from senescing leaves incubated in darkness in suitable medium at 25 degrees C. The protease involved is present in its active form and Lhcb3 is susceptible for proteolytic attack already in fresh leaves, although Lhcb3 degradation does not take place unless undefined extrinsic membrane proteins protecting Lhcb3 are removed in a senescence-dependent manner. It is thus concluded that senescence-dependent Lhcb3 degradation is regulated at the substrate availability level. The protease involved is ATP stimulated, has an optimum activity at pH 7.8, and requires 3 mM added Mg2+ (replicable by micromolar doses of Zn2+) for its proper activity. Studies using typical inhibitors of various classes of proteases indicate that the enzyme is a metalloprotease with disulfide linkage essential for its activity. Micromolar doses of Zn2+ were demonstrated to restore the activity of Lhcb3-degrading enzymes abolished by an ethylenediaminetetraacetic acid pretreatment of the thylakoids and it is inferred that the protease involved is a zinc-binding metalloprotease. Mg2+ was shown to be able to partially replace zinc as the bound ion.     

抗旱性不同的小麦幼苗在水分和盐胁迫下抗氧化酶和多胺的变化

分别对抗旱小麦8139和干旱敏感小麦甘麦8号的幼苗进行两周的水分胁迫和NaCl胁迫,并对其叶片中一些生理指标的变化进行了研究,结果表明,水分胁迫下8139中O2^-和H2O2的含量及膜脂过氧化程度均低于敏感品种,胁迫后第七天与第十四天其中SOD与CAT活性明显高于甘麦8号,盐胁迫下两种小麦中的H2O2,MDA含量及SOD,POX酶活性在各时期均无明显差别,水分胁迫下,8139中多胺（腐胺Put,亚精胺Spd,精胺Spm)含量显著高于甘麦8号,盐胁迫下,两品种中多胺含量有胁迫7d后才表现出差异,由此可见,水分胁迫下两品种清除自由基的能力明显不同。而在盐胁迫下则差别不大。表现在生长上,水分胁迫下8139地上部分干物质的累积量高于甘麦8号,而在NaCl胁迫下两者之间差别不大,该结果表明植物抗旱与抗盐的生理保护机理是不一样的。     

Tolerance to salt stress in maize callus lines with different polyamine content

Four callus lines from immature embryos of a self-crossed maize (Zea mays L.) hybrid cultivar were selected for “high” (two lines) and “low” (two lines) polyamine (PA) levels. Each selected line was exposed to culture media containing no (control) or 1% (0.171 m) NaCl and the relative growth rates were compared after subculture. Low-PA lines appeared to be tolerant to salt stress, while high-PA lines were sensitive. Analysis of PA at the end of the subculture showed that treated calli of sensitive lines had increased their putrescine content in comparison with their control, while putrescine remained constant in tolerant lines. Callus lines were analysed by RAPD (random amplification of polymorphic DNA) markers. One polymorphism (550-bp band) was found, demonstrating a genetic difference between the lines. Received: 18 January 1997 / Revision received: 14 April 1997 / Accepted 15 July 1997     

Cell Death and Growth Recovery of Barley after Transient Salt Stress

3 H-thymidine) in old roots were partially recycled for new tissue formation. This result indicates that cell death may have some physiological roles under transient salt stress. Received 11 January 2000/ Accepted in revised form 29 June 2000