高粱苗(Sorghum vulgare)水分亏缺时所累积的游离脯氨酸的来源

在完全营养液中,用Glu或Ala替代Ca(NO_3)_2为氮源时,在水分胁迫条件下可得到同样程度的Pro累积量。但是用Ser为氮源时,在正常水分条件下Glu和Ala的相对含量较少,Ser和Gln相对含量较高,在水分胁迫条件下,Pro的累积受到抑制。在缺钾营养液中培养时,植株游离氨基酸中Glu和Ala相对量较少,Ser和Gln相对量较高,在水分胁迫条件下,Pro累积也受到抑制。在缺钾营养液中,用Glu或Ala替代Ca(NO_3)_2为氮源时,在水分胁迫条件下Pro的累积可达到甚至超过完全营养液中Pro的相对量。     

不同抗旱品种高粱苗中脯氨酸累积的差异

高粱抗旱品种“3197 B”比不抗旱品种“三尺三”在同样渗透胁迫条件下,要累积更多的游离脯氨酸。未受渗透胁迫前,两品种地上部的总氨基氮和游离氨基氮水平相似。氨基酸组成也相同。六种主要氨基酸分别占总的量和游离氨基酸量的50％和65％左右。受渗透胁迫24h后,总氨基氮水平未变,游离氨基氮增加,两品种的变化相似。因而,品种间脯氨酸累积的差异,似乎不因蛋白质或游离氨基酸的氨基酸组分的不同和蛋白质水解或合成受促进或抑制程度的不同而异。受渗透胁迫后,3197B植株内不但脯氨酸绝对量,而且相对量都超过“三尺三”。脯氨酸合成的潜在能力在3197B和“三尺三”之间有差别。     

外源脯氨酸对盐胁迫下甜瓜幼苗硝酸还原的影响

采用营养液水培方法,以＂雪美＂品种甜瓜（Cucumis melo L.）为材料,研究了外源脯氨酸（Proline）对盐胁迫下甜瓜幼苗叶片和根系硝酸还原的影响。结果表明：（1）盐胁迫提高了甜瓜幼苗叶片和根系内铵态氮（NH4＋-N）和可溶性蛋白含量;降低了硝态氮（NO-3-N）含量和硝酸还原酶（nitrate reductase,NR）活性。（2）外源施用脯氨酸明显地提高了盐胁迫下甜瓜幼苗叶片和根系内NO-3-N和可溶性蛋白含量;降低了盐胁迫下甜瓜幼苗叶片和根系内NH＋4-N含量;增强了盐胁迫下甜瓜幼苗体内NR活性。研究结果表明,外源脯氨酸可以通过调节甜瓜幼苗体内硝酸还原酶活性和氮化合物含量来缓解盐胁迫对甜瓜幼苗植株的伤害。     

环己亚胺对盐诱导游离脯氨酸累积的影响

环己亚胺(CHX)单独作用会增加高梁苗中游离脯氨酸的含量,原因可能有:一是CHX抑制了根的正常吸收功能,导致植株失水,游离脯氨酸增加;二是CHX抑制了蛋白质合成,使总的游离氨基酸累积,从而也表现出游离脯氨酸含量的增加,后者可能更为主要。为此,用CHX研究与脯氨酸合成有关的基因活性化或表达时,一定要考虑CHX单独的作用。NaCl诱导的游离脯氨酸的累积可被CHX处理所抑制。在NaCl处理2～4h内加CHX后,抑制效果几乎可达到100％,以后随CHX处理的时间越长,其抑制作用越小。     

脯氨酸代谢与植物抗渗透胁迫的研究进展

脯氨酸被认为是植物和细菌内的一种相容渗透剂,有助于植物和细菌抵御渗透胁迫。本文就近年来有关植物体内脯氨酸合成和代谢、脯氨酸含量受渗透胁迫的影响情况、脯氨酸合成降解有关的酶及其基因、脯氨酸在细胞中的运输和定位、ＡＢＡ与脯氨酸的诱导合成以及脯氨酸和植物抗渗透胁迫关系的研究进展作了简要综述。     

盐诱导脯氨酸累积过程中亚胺环己酮的抑制作用

微生物中控制脯氨酸合成的渗透调节基因(osm基因)的转移成功及其抗渗透胁迫能力的提高(Csonka 1980,1981,Le Rudulier和Valentine 1981),启发科学家们把注意力投向高等植物,特别是有经济价值的作物(Bodnar等1989,Nelson等1988,1989,Sanada等1989,Higgins等1987)。采用蛋白质合成抑制剂亚胺环     

脯氨酸代谢与植物抗渗透胁迫的研究进展

脯氨酸被认为是植物和细菌内的一种相容渗透剂,有助于植物和细菌抵御渗透胁迫。本文就近年来有关植物体内脯氨酸合成和代谢、脯氨酸含量受渗透胁迫的影响情况、脯氨酸合成降解有关的酶及其基因、脯氨酸在细胞中的运输和定位、ABA与脯氨酸的诱导合成以及脯氨酸和植物抗渗透胁迫关系的研究进展作了简要综述。     

NaCl对小麦苗叶片脯氨酸氧化酶活性和游离脯氨酸累积的影响

在含NaCl营养液中培养的小麦幼苗较之无NaCl营养液中的幼苗。其脯氨酸氧化酶活性降低,而游离脯氨酸含量则升高;培养液的渗透势越低,培养时间越长,则脯氨酸氧化酶的活性越低,且游离脯氨酸的含量越高。去除胁迫后酶活性恢复,脯氯酸含量下降。不同渗透剂对氧化酶活性抑制强弱顺序为MgCl_2>NaCl>甘露醇,引起脯氨酸累积效应的强度顺序为MgCl_2>NaCl>甘露醇。超微结构显示,高NaCl浓度下部分线粒体结构受损伤,膜和嵴部分消失。     

脯氨酸在植物非生物胁迫耐性形成中的作用

植物作为固着生活的有机体,经常暴露在多变且对其生长发育不利的环境条件中,这些生物或非生物的胁迫因子严重影响着植物的生长、发育、生存和分布。脯氨酸在植物抵抗逆境胁迫过程中起着重要的作用。根据国内外的最新研究进展,结合我们的研究成果,对植物体内脯氨酸的代谢途径、渗透调节、抗氧化、分子伴侣、生长发育信号和毒性等方面进行了综述,并对该研究领域作了展望。     

水分胁迫下植物体内游离脯氨酸的累积及ABA在其中的作用

无论是土壤干旱,还是NaCl或PEG所引起的水分胁迫,都使植物体内游离脯氨酸含量明显升高。不同小麦品种反应不一,如对干旱敏感的甘麦8号比抗旱的和尚头、定西24在NaCl和PEG胁迫下游离脯氨酸水平增高得更快,而后者持续的时间较长。土壤干旱胁迫下,小麦各品种之间脯氨酸含量无明显差异。中生植物倒挂金钟(Fuchsia hybrida)和沙生植物猪毛蒿(Artemisia scoparia)在水分胁迫下游离脯氮酸含量均有增高。把小麦幼苗放在5×10~(-5)M ABA溶液中浸根处理,无论在正常或胁迫情况下均能促进游离脯氨酸含量的增高。     

NaHSO3对桃树的生理效应及产量品质的影响

于桃树果实膨大期喷施１００ｐｐｍ ＮａＨＳＯ２可获得增产、优质、早熟的效果。此与ｎａＨＳＯ２能增加叶绿素含量、提高光合速率、比叶重、促进希尔反应,抑制硝酸还原酶、过氧氢酶活性,增加单果重等多重生理效应相关。     

钙在IAA诱导绿豆下胚轴原生质体膨大过程中的作用

含钙培养液(对照)和仅用IAA处理的原生质体的体积和~(45)Ca~(2 )放射性强度均无变化。IAA处理含钙培养液中的原生质体,5min后~(45)Ca~(2 )积累明显增多,体积开始膨大。处理30min时~(45)Ca~(2 )积累最多,此时原生质体的膨大效应最好;随后~(45)Ca~(2 )积累和膨大效应逐渐下降。K~ 、Zn~(2 )、Ba~(2 )、Mg~(2 )等也可在一定程度上代替Ca~(2 )使原生质体体积膨大。原生质体的吸水在膨大中起着一定作用。EGTA、LaCl_3和verapamil均抑制IAA诱导的原生质体~(45)Ca~(2 )积累和体积膨大。说明Ca~(2 )可能在6-BA诱导原生质体膨大的过程中起着重要作用。     

Rhodnius prolixus LIPOPHORIN: LIPID COMPOSITION AND EFFECT OF HIGH TEMPERATURE ON PHYSIOLOGICAL ROLE

Lipophorin is a major lipoprotein that transports lipids in insects. In Rhodnius prolixus, it transports lipids from midgut and fat body to the oocytes. Analysis by thin‐layer chromatography and densitometry identified the major lipid classes present in the lipoprotein as diacylglycerol, hydrocarbons, cholesterol, and phospholipids (PLs), mainly phosphatidylethanolamine and phosphatidylcholine. The effect of preincubation at elevated temperatures on lipophorin capacity to deliver or receive lipids was studied. Transfer of PLs to the ovaries was only inhibited after preincubation of lipophorin at temperatures higher than 55°C. When it was pretreated at 75°C, maximal inhibition of phospholipid transfer was observed after 3‐min heating and no difference was observed after longer times, up to 60 min. The same activity was also obtained when lipophorin was heated for 20 min at 75°C at protein concentrations from 0.2 to 10 mg/ml. After preincubation at 55°C, the same rate of lipophorin loading with PLs at the fat body was still present, and 30% of the activity was observed at 75°C. The effect of temperature on lipophorin was also analyzed by turbidity and intrinsic fluorescence determinations. Turbidity of a lipophorin solution started to increase after preincubations at temperatures higher than 65°C. Emission fluorescence spectra were obtained for lipophorin, and the spectral area decreased after preincubations at 85°C or above. These data indicated no difference in the spectral center of mass at any tested temperature. Altogether, these results demonstrate that lipophorin from R. prolixus is very resistant to high temperatures.     

BA对大麦花药培养中药壁的衰退和植株再生频率的影响

用含20ppm 6-BA的0.1％吐温-80溶液喷施花粉为单核前期的大麦上部叶片和穗部,明显影响大麦花药培养效率。实验结果表明:1)BA处理可明显延缓培养花药的药壁衰退进程。2)BA处理后的花药,在培养期间,其死亡的花粉数比对照大大减少,相反其双核或多核的花粉数比对照明显增加。3)BA处理虽然没有促进大麦花粉愈伤组织的诱导率,但显著地促进愈伤组织的生长。提高愈伤组织成长率,增加可转入分化培养的愈伤组织块数。4)BA处理促进愈伤组织的再分化,尤其是绿苗的分化。     

THE ROLE OF NITROGEN NUTRITION IN HIGH-TEMPERATURE TOLERANCE OF THE KELP,LAMINARIA SACCHARINA (CHROMOPHYTA)1

Mechanisms of high-temperature tolerance in the kelp Laminaria saccharina (L.) Lamour. were examined by comparing a heat-tolerant ecotype from Long Island Sound (LIS), New York, and a population from the Atlantic (ATL) coast of Maine. Greater heat tolerance was not attributable to greater thermal stability of the photosynthetic apparatus: LIS and ATL plants exhibited similar short-term effects of high temperature on photosynthetic capacity (P_max) and quantum yield (estimated as the ratio of variable to maximum chlorophyll fluorescence, F_v/F_m. As LIS plants had consistently higher N and protein content than ATL plants, the interaction between nitrogen nutrition and high-temperature tolerance was examined. When grown under high N supply and optimal temperature (12° C), LIS plants had a higher density of photosystem II reaction centers (RCII), higher activity of two Calvin cycle enzymes (ribulose bisphosphate carboxylase oxygenase [RUBISCO] and NADP-dependent glyceraldehyde-3-phosphate dehydrogenase [G3PDH]), and higher P_max and F_v/F_m than ATL plants. Individual ATL plants, furthermore, exhibited close correlations of RCII density and enzyme activity with N and/or protein content. Variation in RCII density and enzyme activity, in turn, largely accounted for plant-to-plant differences in P_max and F_v/F_m. Relationships among these parameters were generally weak or lacking among individual LIS plants grown under optimal conditions, apparently because luxury N consumption resulted in excess reserves of photosynthetic apparatus components. Exposure of N-replete LIS and ATL plants to a superoptimal temperature (22° C) for 4 days caused an increase in the minimum turnover time of the photosynthetic apparatus (tau) and a decrease in P_max, but had no consistent effect on F_v/F_m RCII density, PSU size (chlorophyll a/RCII), or enzyme activities. When plants were subjected to concurrent N limitation and heat stress, however, LIS and ATL populations exhibited quite different responses. All photosynthetic parameters of N-limited ATL plants declined sharply in response to high temperature, resulting in a negative rate of daily net C fixation. In contrast, LIS plants showed a reduction in PSU size, but maintained other parameters, including daily C fixation, at levels similar to those of N-limited plants at optimal temperature. Overall, the ability of LIS plants to accumulate and maintain high N reserves appears to be critical for heat tolerance and, therefore, for survival during summer periods of simultaneous low N supply and superoptimal temperature. ATL plants, which also experience low summer N supply but not superoptimal temperatures, do not accumulate large reserves of nitrogenous components and are unable to tolerate the combined stress. Because low N supply often co-occurs with high temperatures in temperate marine systems, large-scale declines in algal productivity, such as during El Niño events, are probably due to the interactive effect of N limitation and heat stress.