外源一氧化氮对香蕉幼苗抗冷性的影响

以巴西香蕉(Musa AAA Group Cavendish cv.Brazil)幼苗为试验材料,采用外源一氧化氮(NO)供体硝普钠(SNP)15 μmol·L-1溶液进行冷胁迫(8℃)前处理,考察其冷胁迫和常温恢复过程中抗冷性指标的变化,以探讨外源NO对香蕉幼苗抗冷性的影响.结果表明,在8℃冷胁迫环境下,SNP预处理香蕉幼苗的萎蔫程度较轻,且在常温下恢复快而完全.SNP预处理可以显著降低冷胁迫下香蕉幼苗叶片的质膜相对透性及过氧化氢和丙二醛含量,并显著增加其可溶性蛋白含量.在冷胁迫的前2 d,SNP处理苗的过氧化物酶和抗坏血酸过氧化物酶的活性显著增加,而超氧化物歧化酶和过氧化氢酶的活性则在胁迫的第3天才显著上升,经3 d冷胁迫回温(28℃)后,4种酶的活性均显著提高.可见,适当浓度NO能够通过诱导香蕉幼苗体内的抗氧化酶活性来有效缓解其遭受的冷胁迫损伤.     

Characterization of the platelet aggregation inducer and inhibitor isolated from Crocus sativus

Bulbs of Crocus sativus variety Cartwrightianus were found to contain both a platelet aggregation inducer and inhibitor. The aggregating factor has a Mr of 42 kDa estimated by a Sephadex G75 column and SDS-polyacrylamide slab gel electrophoresis. It was found to lack enzymatic activity such as proteinase, esterase and acid or alkaline phosphatase. The inhibitory factor was also purified to homogeneity by different chromatographic techniques and shows a Mr of 27 kDa as it was estimated by Biogel P30 column and SDS-polyacrylamide slab gel electrophoresis. It was found to possess strong proteinase activity.     

外源NO对转基因白桦外源基因表达及DNA甲基化的影响

为探讨外源NO诱导转基因白桦外源基因表达与基因组DNA甲基化之间的关系,本研究分析了NO供体硝普钠（sodium nitroprusside,SNP）对转基因白桦愈伤组织中外源基因BGT转录的影响,并对此过程中基因组DNA甲基化水平、甲基转移酶基因DRM、MET表达量及生理生化指标进行研究。结果表明：2 mmol·L^-1SNP处理后,转基因白桦防御酶活性、丙二醛（MDA）含量显著升高,表明高浓度NO对白桦细胞正常生命活动产生了伤害;甲基转移酶DRM和MET基因上调表达,基因组DNA甲基化水平由10.6%增加到16.5%,外源基因BGT表达量在6 h时显著增加,3 d时仅为对照的0.46倍,说明转基因白桦外源BGT基因的表达对高浓度NO响应明显且受基因组甲基化水平的影响。本研究揭示了转基因白桦外源BGT基因和甲基转移酶MET、DRM基因对高浓度NO的响应模式,分析了基因组甲基化水平及生理生化特征的变化,为转基因植物生长发育的表观遗传调控和外源基因表达影响机制的研究奠定基础。     

Cloning and Characterization of FLOWERING LOCUS T-Like Genes from the Perennial Geophyte Saffron Crocus (Crocus sativus)

The transition to flowering is one of the most important developmental decisions made by plants. At the molecular level, many genes coordinate this transition. Among these, genes encoding for phosphatidylethanolamine-binding proteins (PEBPs) play important roles in regulating flower time and the fate of inflorescence meristem. To investigate the role of PEBPs in an industrially important crop cultivated for its nutritional and medicinal properties, the monocotyledonous species Crocus sativus L., we have isolated three FLOWERING LOCUS T (FT)-like genes designated as CsatFT1-like, CsatFT2-like, and CsatFT3-like. The isolated genes maintain the exon/intron organization of FT-like genes and encode proteins similar to the members of the PEBP family. Phylogenetic and amino acid analysis at critical positions confirmed that the isolated sequence belongs to the FT clade of the PEBP family phylogeny distinctly from the TERMINAL FLOWER 1 (TFL1) and MOTHER OF FT AND TFL1 clades. Expression analysis indicated differences in the expression of the three FT-like genes in different organs and different expressions during the day–night diurnal clock. Additionally, analysis of isolated promoter sequences using computational methods reveals the preservation of common binding motifs in FT-like promoters from other species, thus suggesting their importance among plant species.     

Effect of Irrigation Water Salinity and Deficit Irrigation on Soil Ions Variation and Uptake by Saffron (Crocus sativus L.) Under Two Planting Methods

Journal of Plant Growth Regulation - A 2-years field experiment in a split-split plot arrangement was considered to investigate the effects of different irrigation water salinity [0.45 (well water,...     

外源NO提高小麦幼苗抗旱性的生理机制

以小麦(Triticum aestivum L.)品种'豫麦49'为材料,采用50μmol·L-1SNP(NO供体)处理自然干旱和PEG模拟干旱下的小麦幼苗,分析外源NO对水分胁迫下小麦幼苗相对含水量、光合速率、细胞膜透性以及茎叶中关键性离子含量的影响.结果显示:自然干旱10 d后,对照组幼苗几乎全部枯死,而50μmol·L-1SNP处理幼苗并未发生枯死,其幼苗在旱后复水2 d后能完全恢复正常生长;在25%PEG-6000模拟干旱条件下,50μmol·L-1SNP处理也能明显改善受胁迫小麦幼苗长势.50μmol·L-1SNP处理使模拟干旱胁迫下小麦叶片的相对含水量显著提高15.98%,净光合速率(Pn)、气孔导度(Gs)分别显著提高47.11%和42.86%,而胞间CO2浓度(GI)显著降低了8.19%;也使小麦组织浸出液电导率显著降低30%,茎叶的K 含量显著增加24.55%(P<0.01).研究发现,外源NO既可通过降低小麦幼苗叶片蒸腾来维持较高的叶片相对含水量,缓解因干旱缺水对植株的伤害;又可增加K 在茎叶中积累,减轻干旱胁迫对小麦幼苗细胞膜伤害,维持干旱胁迫下小麦幼苗较高的光合速率,以确保植株正常生长和有机物质积累.     

极端干旱区疏叶骆驼刺叶绿素荧光对人工水分干扰的响应特征

选取塔里木河下游天然植被恢复示范区的疏叶骆驼刺(Alhagi sparsifolia Shap.)为研究对象,测定每年引水灌溉2次(每次0.42m3/m2)、1次和不灌溉(CK)处理下疏叶骆驼刺的实际光化学量子产量(ΦPSⅡ)、电子传输速率(ETR)和光化学猝灭系数(qP)等叶绿素荧光参数及其叶水势变化,探讨疏叶骆驼刺对人工水分干扰的叶绿素荧光响应特征。结果表明:(1)随着灌溉量的减少,疏叶骆驼刺叶水势呈显著降低的趋势,并在CK下达到最低。(2)同期疏叶骆驼刺qP、ΦPSⅡ、ETR、最大光量子产量(Fv/Fm)、叶绿素含量和光饱和点均随着灌溉量的减少呈先增加后降低的趋势,非光化学淬灭系数(NPQ)和调节性能量耗散(YNPQ)则呈先降低后增加的趋势。(3)与每年1次灌溉量处理相比,不灌溉和每年2次的灌溉量处理下疏叶骆驼刺发生了光抑制,光能捕获效率与光化学反应能量下降,热耗散能力提高。研究认为,灌溉量过高(每年2次,0.84m3/m2)或不灌溉均会限制疏叶骆驼刺光化学效率和光和活性,适时适量的(春季灌水1次,0.42m3/m2)水分补给更有利于疏叶骆驼刺适应干旱胁迫并维持正常光合生长。     

Antistress Effect of Nitric Oxide

Rat strains feature different resistances to stress. The increased production of nitric oxide (NO) in the August strain prevents the appearance of ulcerous lesions of gastric mucosa and behavioral changes induced by restraint stress. Wistar rats feature a lower level of NO production and are more sensitive to restraint stress compared to the August rats according to both the ulcerous gastric lesions and behavioral parameters. The stress-induced release of catecholamines was mimicked by experimental hyperfunction of the dopaminergic (DA) system induced by L-DOPA. The NO synthase inhibitor N-nitro-L-arginine (L-NNA) enhanced the L-DOPA-induced behavioral changes. This effect was more pronounced in the August strain. The administration of the exogenous NO donor, dinitrosyl iron complexes (DNIC), limited the behavioral disturbances induced by L-DOPA in both rat strains. The protective effect of DNIC in conditions of the DA system hyperfunction is similar to the effect of a D₂blocker sulpiride. Thus, NO has a central antistress effect apparently mediated by limiting the release of catecholamines.     

The Effect of Nitric Oxide on Bacteria

Nitric oxide, as well as several other oxides of nitrogen, were assayed for their antibacterial action. It is shown that nitric oxide has virtually no effect on bacteria, whereas both NaNO₃ and NaNO₂ appear to have either neutral or stimulatory effects. It is suggested that the formation of nitrous acid is mainly responsible for the quantitative as well as the qualitative changes that occur in the bacterial flora of cured meat. A pH-dependent “nitrite cycle” is presented to account for the production of nitrous acid in cured meat systems.     

外源NO对铝毒下水稻根系生长和抗氧化系统的影响

以水稻品种‘浙辐802’为材料,采用水培法研究铝毒下外源NO对幼苗根系生长、活性氧产生和抗氧化酶活性的影响,探讨外源NO提高水稻耐铝性的生理生化机制。结果显示:(1)0.05mmol/L Al显著抑制水稻根系生长,促使根尖Al、胼胝质、过氧化氢(H2O2)和超氧阴离子自由基(O-·2)含量显著增加;而外源0.1mmol/L的NO供体亚硝基铁氰化钠(sodium nitroprusside,SNP)预处理能使铝毒下水稻幼苗根相对伸长率及根尖NO含量分别增加34.96%和12.86%,根尖Al和相对胼胝质含量分别下降83.04%和31.93%,表明NO可部分缓解铝毒害,且这种作用与内源NO含量变化有关。(2)外源NO同时使铝毒下水稻幼苗根尖H2O2和O-·2含量分别下降15.43%和12.93%,使超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性显著上升,且外源NO的该种作用可以被0.075mmol/L NO清除剂(carboxy-PTIO,cPTIO)所逆转。研究表明,外源NO在调节活性氧代谢以维持细胞膜结构稳定,进而有效减轻Al对水稻根系的损伤上起着重要作用。     

Effect of Nitric Oxide on Anammox Bacteria

The effects of nitrogen oxides on anammox bacteria are not well known. Therefore, anammox bacteria were exposed to 3,500 ppm nitric oxide (NO) in the gas phase. The anammox bacteria were not inhibited by the high NO concentration but rather used it to oxidize additional ammonium to dinitrogen gas under conditions relevant to wastewater treatment.Nitric oxide (NO) has several different roles in bacteria, fungi, and mammals (24). In nitrogen cycle bacteria, it acts as an intermediate and cell communication/signal transduction molecule. On the other hand, NO is a highly reactive and toxic compound that contributes to ozone depletion and air pollution (5). Due to its reactive nature, many bacteria employ an arsenal of proteins (those encoded by norVW, as well as bacterial globins, heme proteins, etc.) that are used to detoxify NO to the less-reactive and more-stable nitrous oxide (N₂O) (24). Still, N₂O is a very effective greenhouse gas and an unfavorable constituent in the off-gases from nitrification/denitrification nitrogen removal systems (4). The presence of gene(s) encoding cytochrome cd₁ nitrite reductase (EMBL accession no. {"type":"entrez-protein","attrs":{"text":"CAJ74898","term_id":"91201838","term_text":"CAJ74898"}}CAJ74898), flavorubredoxin NorVW (accession no. {"type":"entrez-protein","attrs":{"text":"CAJ73918","term_id":"91200863","term_text":"CAJ73918"}}CAJ73918 and {"type":"entrez-protein","attrs":{"text":"CAJ73688","term_id":"91200638","term_text":"CAJ73688"}}CAJ73688), and bacterial hemoglobin (accession no. {"type":"entrez-protein","attrs":{"text":"CAJ72702","term_id":"91203063","term_text":"CAJ72702"}}CAJ72702) in the genome of Kuenenia stuttgartiensis led to the proposal that NO also plays this dual role (metabolic versus toxic) in anammox bacteria (Fig. ​(Fig.1)1) (10, 20). This has ramifications for both application and metabolism of anammox bacteria. The source of NO in an anammox reactor could be the activity of other community members (ammonium-oxidizing or denitrifying bacteria) or high concentrations of nitrite in the influent wastewater stream. Full-scale anammox reactors typically contain a significant population of ammonium-oxidizing bacteria (AOB). In the single nitritation-anammox reactors, these carry out the conversion of 50% of the ammonium in the wastewater to nitrite (6). It has been shown that AOB may produce significant amounts of NO (2, 7), and recently it was reported that NO and N₂O could be emitted from these reactors up to 0.005 and 1.2% of the total nitrogen load to the reactor, respectively (6, 23). NO may inhibit the anammox bacteria and could also be further reduced to N₂O in these reactors (6, 23). It is presently unknown whether anammox bacteria contribute to the NO or N₂O emissions, although it has been suggested previously that anammox bacteria do not produce N₂O under physiologically relevant conditions (10). Nevertheless, if conversion of NO could be coupled to anaerobic ammonium oxidation, the toxic air pollutant NO would facilitate further removal of ammonium in full-scale anammox bioreactors. In the present study, we investigated the effect of very high NO fluxes on anammox bacteria.Open in a separate windowFIG. 1.The hypothetical anammox pathway with possible routes of NO removal. Solid black arrows: anammox pathway, including nitrite oxidation to nitrate; gray arrow, possible detoxification pathway to N₂O (not observed in the bioreactor); dashed gray arrow, NO oxidation to nitrite/nitrate (not possible under anoxic conditions).NO has been described many times as a potent inhibitor of nitrogen cycle bacteria; aerobic ammonium oxidizers, nitrite oxidizers, and denitrifiers were all inhibited by concentrations as low as a few micromolar units (1, 18, 24). In a previous study, it was suggested that “Candidatus Brocadia anammoxidans” could tolerate up to 600 ppm NO (approximately 1 mg NO·day⁻¹ NO load) (16). In the reported experiments, without direct measurement of nitrous oxide (N₂O) in the effluent gas stream, it was postulated that NO was reduced to N₂O (16). In the present study, we used a carefully monitored sequencing batch reactor (SBR) to further our understanding of the effect and fate of NO in a laboratory-scale anammox reactor under conditions which are relevant in wastewater treatment plants.An SBR (working volume, 3.5 liters) consisting of approximately 80% of the anammox bacterium “Candidatus Brocadia fulgida” and no detectable aerobic ammonium oxidizers (determined by fluorescence in situ hybridization (FISH) as described previously [15]) was used in the present study. Before the first introduction of NO into the reactor, the influent (synthetic wastewater) (21) was supplied to the reactor at a flow rate of 1.4 ml·min⁻¹ with nitrite and ammonium concentrations (assayed as previously described [9]) at 45 and 39 mM, respectively (corresponding to a total of 2,370 mg N·day⁻¹). All nitrite was consumed in the reactor, while 2 mM ammonium was still present in the effluent. For every 1 mol of ammonium, 1.22 mol of nitrite was consumed, similar to the previously determined anammox stoichiometry (19). NO was first introduced at a concentration of 400 to 600 ppm in the gas phase at a flow rate of 10 ml/min (CLD 700EL chemiluminescence NOx analyzer, detection limit of 0.1 ppm NO, with 15 ml/min Ar/CO₂ as the dilution gas [a load of 25 to 28 mg NO·day⁻¹]; EcoPhysics, Michigan). During this period, 45% (±6%) of the supplied NO was removed from the system. Initially, there was no detectable change in the ammonium and nitrite removal efficiencies and no detectable nitrous oxide (N₂O) in the flue gas (analyzed with an Agilent 6890 gas chromatograph). It is most likely that NO was converted to N₂, but the increase in the N₂ concentrations in the off-gas was below the detection limit (1,000 ppm).At day 49, the influent NO concentration was increased to 3,500 ppm (640 mg NO·day⁻¹ load). Simultaneously, the stirring speed of the reactor was increased from 200 to 600 rpm to enable better mass transfer to the flocculent anammox biomass. The increase in the stirring speed did not result in any disturbance in the floc size and settling ability of the biomass but did lead to a much higher level of NO removal (128 mg NO·day⁻¹) by the anammox bacteria. The converted NO could theoretically be converted to N₂O via detoxification enzymes or coupled to ammonium oxidation (Fig. ​(Fig.1).1). Surprisingly, there was no change in the nitrite removal capacity of the bioreactor, suggesting that NO was not a substrate preferred over nitrite. Nitrate concentrations (assayed according to the method in reference 9) were stable around 7.2 mM (±0.7 mM). Theoretically, as anammox bacteria reduce NO, they could oxidize a larger proportion of nitrite to nitrate (Fig. ​(Fig.1)1) to increase their capacity for CO₂ fixation; however, such an increase in nitrate production was not observed (or could not be discriminated by the method used [sensitivity, 100 μM]). During this phase of the experiment, the effluent ammonium concentration gradually decreased to below the detection limit (Fig. ​(Fig.2).2). There was only a minimal N₂O (0.6 ppm) emission from the system, and the total N₂ production increased from 3,060 to 3,680 mg N₂·day⁻¹. This indicated that NO reduction was coupled to the catabolism of the anammox bacteria rather than being detoxified by anammox or other community members. To the best of our knowledge, this was the first time that such a high load of NO was not found to be toxic to the nitrogen cycle bacteria. In a previous study, an NO load of 1 mg NO·day⁻¹ was reported to be toxic to anammox bacteria, most probably due to the fact that the experiments were conducted with biomass that had a 100-fold lower cell density and 10-fold lower activity compared to the current enrichment cultures. Furthermore, the NO conversion in the current experiments was stoichiometrically coupled to ammonium oxidation and not converted to N₂O, indicating that the previously reported N₂O emissions from full-scale anammox bioreactors originated not with the anammox bacteria but rather with other community members as hypothesized previously (8).Open in a separate windowFIG. 2.Ammonium concentration in the effluent of the anammox bioreactor. Dashed lines indicate the trend of effluent ammonium concentration during different phases of the reactor operation. Black arrows indicate the manipulations to influent NO stream, and the gray arrow points to an increase in the influent ammonium concentration. d, day.To determine if there could be more NO-dependent ammonium removal, the influent ammonium concentration was first increased to 41 mM (day 80) and then to 43 mM (day 81). This resulted in a slow but gradual increase in the effluent ammonium concentration, and additional ammonium did not appear to be completely converted, most probably due to NO mass transfer limitations. As a result of the higher level of ammonium removal, the observed anammox stoichiometry in the reactor decreased from 1.22 to 0.91 (nitrite/ammonium). Between days 95 and 131, the NO supply to the reactor was turned off, which resulted in an average ammonium concentration of 3.3 mM (±0.9 mM) in the effluent. Following this period, on day 132, the NO load on the reactor was increased back to 640 mg NO·day⁻¹ (Fig. ​(Fig.2).2). As a result, the effluent ammonium concentration gradually decreased again to an average of 1.5 mM (±0.36 mM). The highest level of NO removal achieved in this period was 371 mg NO·day⁻¹. When the NO supply was turned off on day 165, ammonium concentrations increased back to 3.5 mM (±0.71 mM).During the course of the experiment, the biodiversity of the reactor was monitored using FISH and 16S rRNA gene sequence analysis as described previously (15) with probes specific to eubacteria (3), Planctomycetes (13), anammox bacteria (15), “Ca. Brocadia fulgida” (11), and a variety of aerobic ammonium-oxidizing bacteria (12, 22). Before the experiments started and throughout the cultivation of the anammox bacteria with NO, the only detectable anammox species (with FISH and 16S rRNA gene sequence analysis) was “Candidatus Brocadia fulgida.”In the present study, we showed that 2 mM ammonium (4.5% of the influent concentration) could be removed by anammox bacteria via direct coupling to NO reduction. These observations support the proposal of NO as an intermediate of the anammox reaction and have two consequences for application of the anammox process for nitrogen removal. First, we obtained strong indications that previously reported N₂O emissions (6, 8) from full-scale anammox reactors were not generated by anammox bacteria. In our experiments, even under a very high load of NO, there was hardly any detectable N₂O in the effluent gas stream. The competition for nitrogen oxides by denitrifying and anammox bacteria needs further study but may ultimately be used to design operational conditions that would reduce or even prevent NO and N₂O emissions from full-scale nitritation-anammox reactors. Second, by implementing the results of this study, in the future the anammox process could be designed to remove NO from flue gases. Since NO is mostly emitted together with O₂, this could be achieved by the combination of anammox and aerobic ammonium-oxidizing bacteria, for example, with CANON (completely autotrophic nitrogen removal over nitrite)- or OLAND (oxygen-limited autotrophic nitrification-denitrification)-type reactor systems (14, 17).     

外源一氧化氮对NaCl胁迫下番茄幼苗生长和光合作用的影响

以2个耐盐性不同的番茄品种为材料,研究了外源NO供体硝普钠(SNP)处理对100mmol·L-1NaCl胁迫下番茄幼苗生长和光合作用的影响。结果表明:外源NO能使盐胁迫下的番茄幼苗叶片叶绿素含量、净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)升高,胞间CO2浓度(Ci)下降,叶绿素荧光参数Fv/Fm、Fv/Fo和T1/2增高,脯氨酸和可溶性糖含量升高。可见,外源NO有利于番茄幼苗对光能的捕获和转换,促进番茄的生长,降低盐胁迫对番茄的抑制作用。     

Effects of Chronic Nitric Oxide Inhibition on the Renal Excretory Response to Leptin

Objective: Previous investigations have demonstrated that leptin promotes natriuresis with a renal tubular effect. However, the mechanisms involved in this response are unclear. The present study was designed to examine the hypothesis that the natriuretic response to leptin in normotensive Sprague‐Dawley rats is regulated by nitric oxide (NO). Research Methods and Procedures: The hemodynamic and renal excretory effects of intravenous bolus administration of pharmacological doses of synthetic murine leptin were examined in groups of control Sprague‐Dawley rats (n = 8), Sprague‐Dawley rats treated for 4 days with the NO synthase inhibitor Nω‐nitro‐l‐arginine methyl ester (l‐NAME) (n = 8), and Sprague‐Dawley rats treated for 4 days with l‐NAME followed by acute treatment with sodium nitroprusside (n = 8). Results: In the control group (n = 8), an intravenous bolus of leptin, 400 μg/kg body weight, increased urinary sodium excretion 4‐ to 6‐fold. In the Sprague‐Dawley rats chronically administered l‐NAME (n = 8), an intravenous bolus of 400 μg/kg of leptin did not increase sodium excretion. Acute sodium nitroprusside infusion to Sprague‐Dawley rats chronically treated with l‐NAME (n = 8) was associated with partial restoration of the sodium excretory response to leptin administration. Discussion: Collectively, these results are interpreted to suggest that the natriuretic and diuretic responses to leptin observed in the Sprague‐Dawley rat require a functional NO system.     

外源一氧化氮供体硝普钠对红树植物桐花树气孔运动的调控效应

探索一种用材简单、操作方便、真实性强的观察红树植物桐花树叶片气孔的制片技术,并利用该技术研究不同浓度、不同处理时间的一氧化氮（NO）供体硝普钠（sodium nitroprusside,SNP）对桐花树气孔开闭的影响,探讨了NO调控的气孔运动与外源Ca^2＋的关系以及NO与H202在调节气孔运动过程中的关系。结果表明：在搅碎法、指甲油印迹法、牛皮胶印迹法三种观察气孔方法中,牛皮胶印迹法是观察气孔开度变化的最佳方法。NO能够诱导桐花树气孔快速关闭,且表现出明显的时间效应与浓度效应。NO导致的气孔关闭与Ca^2＋的参与有密切关系,NO与H,q存在明显的协同效应,可以促进气孔关闭。     

藏红花凝集素分子化学修饰与其活性的关系

对甘露糖专一性结合藏红花凝集素 (Crocussativuslectin ,CSL)分子进行化学修饰 ,测定酿酒酵母 (S .cerevisiae)凝集活性和寡糖专一性结合活性的变化 .实验结果表明 ,Cys的修饰与活性无关 ,Arg、Tyr和His的修饰降低了CSL分子的酵母凝集活性和寡糖结合活性 ,但对CSL的CD光谱无显著影响 ,表明其为凝集素的活性氨基酸残基 .Glu和Asp的化学修饰可使CSL的凝集活性大幅度降低 ,与特异性寡糖的亲和力增大 ,CD光谱变化明显 ,提示CSL分子中的Glu和Asp对其空间结构影响较大 ,氨基酸羧基的修饰导致CSL构象改变 ,蛋白与寡糖的结合位点暴露 ,可有效结合的位点数增加     

外源赤霉素对心里美萝卜幼苗花青素的影响

花青素是植物体内广泛存在的一类天然色素,具有重要的生理功能。花青素合成途径可受多种因素调控,其中植物生长激素赤霉素（gibberellic acid,GA）对其的调控作用报道较少。本文用不同浓度的赤霉素处理心里美萝卜幼苗,以探讨它对花青素含量的影响。结果表明,外源GA3处理显著增加了萝卜幼苗的下胚轴长度,并提高了下胚轴中α-淀粉酶活性;显著降低下胚轴中花青素的含量。1 μmol/L GA3处理效果较好;处理后第3 d和第5 d,花青素合成的关键酶查尔酮合酶、查尔酮异构酶和花青素还原酶编码基因的表达水平均低于对照组。同时,外源GA3显著诱导过氧化物酶活性的升高。上述结果表明,外源赤霉素可能通过下调花青素合成基因的表达,提高过氧化物酶活性和促进下胚轴伸长生长降低花青素的水平。     

外源NO对南方红豆杉幼苗光合色素及抗氧化酶的影响

以4年生南方红豆杉幼苗为实验材料,通过对南方红豆杉幼苗喷施不同浓度外源一氧化氮（NO）供体硝普钠溶液（0、0.01、0.1、0.5和1 mmol·L^-1SNP）,测定光合色素含量、抗氧化酶活性、丙二醛（MDA）含量和过氧化氢（H₂O₂）含量等生理指标,以探讨不同浓度外源NO对南方红豆杉叶片光合色素和抗氧化酶的影响。结果表明：喷施低浓度（0.01、0.1 mmol·L^-1）SNP可显著提高南方红豆杉叶片的叶绿素a、叶绿素b、类胡萝卜素和总叶绿素含量,增加叶绿素a/b的比值,而喷施高浓度（0.5、1 mmol·L^-1）SNP降低了叶片的光合色素含量。随着外源NO供体浓度的增加,叶片过氧化氢酶(CAT)活性显著增加,过氧化物酶(POD)活性先增加后降低。此外,处理前期,低浓度SNP处理明显提高了抗坏血酸过氧化物酶(APX)活性,而高浓度SNP处理显著降低了APX活性,处理后期APX活性随SNP浓度的增加而显著下降。喷施低浓度SNP可有效提高超氧化物歧化酶(SOD)活性和增加可溶性蛋白含量,降低MDA和H₂O₂的含量,而喷施高浓度SNP显著增加了MDA和H₂O₂的含量。因此,低浓度的SNP（<0.5 mmol·L^-1）处理南方红豆杉幼苗,可增加其叶绿素含量,提高抗氧化酶活性,降低MDA和H₂O₂的含量,而高浓度的SNP（≥0.5 mmol·L^-1）处理会降低叶绿素含量,提高H₂O₂含量,增加细胞膜质过氧化程度,从而对南方红豆杉幼苗造成一定伤害。     

外源一氧化氮对镉胁迫下黄瓜幼苗生长、活性氧代谢和光合特性的影响

镉是植物生长的非必需元素,它具有很大的生物毒性,与其它重金属相比,更易被植物吸收积累。通过采用营养液水培试验的方法,研究了外源一氧化氮（Nitric oxide,NO）对不同浓度Cd^2＋（100μmol L^-1．300μmol L^-1,500μmol L^-1）胁迫下黄瓜幼苗生长、叶片光合特性以及活性氧代谢的影响。结果表明：300μmol L^-1NO供体硝普钠（Sodium nitrop russide,SNP）能显著缓解镉胁迫时黄瓜植株造成的伤害,对300μmol L^-1 Cd^2＋处理的黄瓜幼苗缓解效果最好,可提高幼苗的生长量,增强幼苗叶片超氧物歧化酶（SOD）、过氧化物酶（POD）活性;提高了叶片叶绿素和脯氨酸（Pro）含量;降低了叶片内二醛（MDA）含量。     

外源NO对增补UV-B辐射下兴安落叶松幼苗叶片光合色素和叶绿素荧光特性的影响

在增强UV-B辐射下,以3年生兴安落叶松幼苗为实验材料,研究了外源NO供体硝普钠(Sodium nitroprusside,SNP)对幼苗的光合色素（Chla、Chlb和Car）和叶绿素荧光参数的影响。方差分析结果表明0.5 mmol·L^-1的SNP对增补UV B胁迫下的兴安落叶松幼苗产生显著影响。0.5 mmol·L^-1的SNP能够显著抑制增补UV-B辐射后光合色素、F_v/F_m、Φ_PSⅡ、F_v′/F_m′和qP的明显下降以及Chla /Chlb、F_o和NPQ的升高。表明了外源NO能够减轻UV-B辐射胁迫下兴安落叶松幼苗光合反应中心的生理损伤,从而增强兴安落叶松幼苗对增补UV-B辐射胁迫环境的适应能力。