干旱胁迫对银沙槐幼苗叶绿体和线粒体超微结构及膜脂过氧化的影响

以沙生植物银沙槐(Ammodendron argenteum)幼苗为实验材料,利用透射电镜技术,结合丙二醛(MDA)和细胞膜透性的测定,观察干旱胁迫对银沙槐子叶期幼苗的叶肉细胞及下胚轴细胞超微结构的变化,分析干旱胁迫对银沙槐幼苗细胞超微结构和膜脂过氧化的影响。结果显示:随着干旱胁迫的加剧,叶绿体变形、外被膜波浪状、断裂不完整。同时,基粒和基质类囊体膜结构模糊,基粒弯曲、膨胀、排列混乱;线粒体膜完整性低、内部嵴消失、空泡化。细胞膜透性和膜脂过氧化产物MDA含量均升高,显著高于对照(P0.05),细胞膜结构受到破坏,细胞膜脂过氧化作用增强。子叶的细胞膜透性和MDA含量显著高于下胚轴(P0.05),细胞器形态变化早于下胚轴,表明下胚轴耐旱性相对于子叶较强。子叶中线粒体受损晚于叶绿体,线粒体的耐旱性要比叶绿体强。不同组织间及同一组织不同细胞器之间对干旱胁迫反应的差异,可能是植物组织细胞应对外界不利环境的一种防御反应。干旱胁迫下超微结构的变化反映了细胞内膜系统的紊乱和伤害,而膜系统的伤害可能是脂质过氧化作用增强的结果。     

干旱胁迫对3种苹果属植物叶片解剖结构、微形态特征及叶绿体超微结构的影响

采用树脂包埋块半薄/超薄切片技术，通过光镜（LM）、扫描电镜（SEM）和透射电镜（TEM）方法，研究了轻度、中度和严重干旱胁迫对楸子（Malus prunifolia）、新疆野苹果（M. sieversii）和平邑甜茶（M. hupehensis）叶片组织解剖结构、表皮微形态特征（气孔密度、大小及角质层厚度）及叶绿体超微结构的影响。光镜观察结果表明，与对照相比，干旱胁迫条件下3种苹果属植物叶片厚度、栅栏组织厚度及叶肉组织结构紧密度（CTR）都显著减小（P＜0.05），而海绵组织厚度与叶肉组织结构疏松度（SR）均显著增加（P＜0.05）。扫描电镜观察结果显示，3种苹果属植物幼叶气孔密度在干旱胁迫下显著增大（P＜0.05），而气孔宽度、开张比及其开张度明显下降。透射电镜观察结果表明，在干旱胁迫下，楸子和新疆野苹果上下角质层厚度逐渐增加，而平邑甜茶的随干旱胁迫程度增加呈先增后减的变化；在轻度和中度水分胁迫下，叶绿体膨胀变形，淀粉粒变小消失，基粒片层排列松散减少，类囊体腔扩大；在严重胁迫条件下，叶绿体膨胀近圆形，叶绿体膜破裂，类囊体严重泡化开始解体。与平邑甜茶相比，严重水分胁迫下楸子和新疆野苹果叶绿体超微结构损伤较小，能较好地保持细胞结构的完整性。     

土壤干旱下玉米幼苗解剖结构的伤害进程

石蜡切片和电镜观察发现,土壤中度干旱下,玉米叶片气孔密度增大,气孔的长、宽度明显减小;叶表皮细胞失水皱缩,"花环型结构"逐步被破坏;根皮层细胞体积变小,维管束杂乱分布;茎薄壁组织由排列整齐变为无序;叶肉细胞叶绿体在形状上膨胀麦圆,脂类小滴增多增大,叶绿体被膜逐渐膨散乃至断裂,叶绿体片层结构由排列整齐变为混乱,且间质片层对水分胁迫较敏感.     

新疆滨藜属植物叶表皮微形态学及叶的比较解剖学研究

本研究采用了石蜡切片法，电子显微镜扫描的方法，对新疆分布的滨藜属１２种及２变种植物进行了研究，观察到滨藜属植物叶的结构可分为三种类型：全栅型、双栅型、单栅型。叶表皮附属物表皮毛、角质层都非常多。表皮毛－光状毛，在幼叶及茎顶泡状毛为生活状态，在成熟的叶上泡状毛破裂、死亡，覆盖在叶的表面；角质层在叶的上、下表皮细胞表面分布，可分为皱纹状角质层和脊状角质层。以上特点都是滨藜属植物叶对干旱的环境条件的适应     

四翅滨藜和多枝柽柳对土壤干旱的响应差异

在干旱区防护林建设中,选择抗逆性和适应力强的植物树种是关键。通过模拟不同干旱梯度的盆栽控水试验来比较塔里木盆地引种植物四翅滨藜和乡土植物多枝柽柳对干旱胁迫生态适应性差异。结果表明：（1）随着干旱程度增加,四翅滨藜和多枝柽柳叶片含水量均逐渐降低,保水力、脯氨酸含量、相对电导率逐渐增大。四翅滨藜和多枝柽柳的可溶性糖含量、丙二醛含量分别在轻度、重度干旱下达最大值,多枝柽柳的增幅更大。（2）四翅滨藜和多枝柽柳POD活性逐渐增大,重度干旱下,多枝柽柳较对照增加的百分比约为四翅滨藜的3倍;在中度干旱下SOD活性最大,多枝柽柳较对照增加的百分比约为四翅滨藜的5倍。多枝柽柳2种酶活性变化均大于四翅滨藜。（3）四翅滨藜和多枝柽柳叶绿素含量均为:轻度干旱>对照>中度干旱>重度干旱,多枝柽柳的净光合速率、蒸腾速率、气孔导度和胞间二氧化碳浓度均逐渐降低,轻度干旱对四翅滨藜叶绿素和光合能力有略微促进作用。（4）相关性和主成分分析结果显示,干旱胁迫下多枝柽柳各性状间的联系更紧密,四翅滨藜不易改变性状和性状之间的联系,相对保守。四翅滨藜受到干旱胁迫的影响较小,其干旱适应性略强于多枝柽柳。     

干旱胁迫对马铃薯叶片超微结构及生理指标的影响

选用不耐旱品种‘费乌瑞它’、耐旱性较强品种‘东农308’和耐旱品种‘晋薯2号’的脱毒试管苗为材料,利用含有20%PEG-6000的MS液体培养基进行水分胁迫处理,研究干旱胁迫对马铃薯叶片细胞超微结构和生理指标的影响。结果表明:叶绿体对干旱胁迫反应最为敏感且受损伤最重,胁迫后叶绿体外形肿胀变圆,片层开始松散,间隙增大,甚至出现孔洞。线粒体次之,外膜破坏,嵴减少。对细胞核的影响相对较小。‘费乌瑞它’超微结构损伤最严重,‘东农308’次之,‘晋薯2号’伤害最轻。超微结构发生变化的同时,各项生理指标也随之改变。3个品种丙二醛(MDA)含量升高48.89%~243.27%,并且都达到极显著水平;过氧化物酶(POD)活性升高2.06%~32.98%,‘费乌瑞它’和‘晋薯2号’分别达到极显著和显著水平;不同品种的超氧化物歧化酶(SOD)活性和叶绿素含量变化趋势不一致。上述指标中,丙二醛含量和叶绿体超微结构变化显著,并能较好地表现出不同品种之间抗旱性的差异。     

水稻基腐病菌毒素对烟草活性氧代谢及细胞超微结构的影响

 用水稻基腐病菌毒素注射烟草叶片后,烟草细胞中O₂^-_·和NO大量增加,H₂O₂含量明显降低,SOD、CAT和POD等酶的活性发生变化。毒素引起烟草细胞死亡,但没有细胞程序性死亡(PCD)的DNA梯特征。病菌毒素处理烟草叶片后,电导率增大,细胞膜透性增加。电镜观察烟草细胞的超微结构表明,毒素处理8h后,叶绿体变形,叶绿体基质片层大部分消解,基粒结构消失,叶绿体外膜和内膜剥离,质壁分离和细胞膜内陷,细胞器消解;处理48h后,细胞内含物完全消解,细胞膜消失,细胞壁皱缩变形。本研究表明,毒素引起烟草细胞死亡与植物抗病反应HR中细胞坏死的生理生化机制不同,但可能存在相似的信号传导途径。     

不同条件下黑果枸杞叶片气孔开度和超微结构的变化

为了探究黑果枸杞的抗旱性,以及提高其抗旱性喷施水杨酸的适宜浓度,采用人工控制水分模拟干旱胁迫条件,以黑果枸杞幼苗为实验材料,研究在不同程度干旱胁迫下喷施不同浓度(0、0.1和0.5 mmol·L-1)外源水杨酸(salicylic acid,SA)对黑果枸杞叶片结构的影响。结果显示:黑果枸杞叶片表皮气孔开度随干旱胁迫程度加深呈递减趋势,轻度(D1)和中度(D2)干旱胁迫处理组较对照(CK)显著减少(P0.05),分别较对照减小23.2%、24.1%,重度(D3)干旱胁迫处理组较其他3组显著减少(P0.05)。随着喷施外源SA浓度的增加,各组黑果枸杞叶片表皮气孔开度显著减小(P0.05)。黑果枸杞叶片相对电导率随干旱胁迫程度加深而递增,中度和重度干旱胁迫处理组较对照显著增加(P0.05),分别增加了48.72%和72.19%。随着喷施外源SA浓度的增加,重度干旱胁迫下黑果枸杞细胞膜透性显著减小(P0.05)。黑果枸杞叶片细胞在轻度干旱胁迫下细胞器变化不明显,但在中、重度干旱胁迫下细胞器破坏较大尤其是叶绿体,喷施SA后,发现细胞器受到的伤害得到缓解,线粒体嵴结构明显可见,叶绿体中也未发现存在大量的嗜锇颗粒或淀粉粒。通过3组指标的分析,说明黑果枸杞可以抵抗轻度干旱胁迫,但在中度或重度干旱胁迫时,喷施适宜浓度(0.5 mmol·L-1)的外源SA可提高黑果枸杞的抗旱性。     

不同水位条件对刚毛柽柳叶绿体超微结构的影响

通过研究塔里木河下游不同水位条件下'刚毛柽柳营养枝和抱茎叶中叶绿体超微结构的变化与其丙二醛(MDA)含量变化的关系.研究表明:当地下水位达到7.68 m时,刚毛柽柳营养枝中叶绿体的数量减少,被膜结构变模糊,基粒片层疏松,淀粉粒数量减少,嗜锇颗粒增加;而抱茎叶在地下水位达到6.68 m时就表现出上述特征.随着地下水位的降低,刚毛柽柳枝叶中MDA含量明显增加,且从7.68 m处开始增加幅度明显大于前期.说明刚毛柽柳营养枝中的叶绿体比抱茎叶中的叶绿体更能耐受干旱胁迫.     

干旱胁迫对藜叶片干旱诱导蛋白的影响

采用SDS-PA GE(十二烷基硫酸钠-聚丙烯酰胺)凝胶电泳法进行蛋白质的分离,研究干旱胁迫对藜叶片干旱诱导蛋白的影响.结果表明:干旱胁迫10 d,中度干旱藜的叶片110.3 KD和103.9 KD及24.8 KD,22.7KD,21.0 KD蛋白谱带明显加强,重度干旱胁迫下22.7 KD,21.0 KD蛋白谱带增强,但弱于中度干旱胁迫;干旱胁迫15 d,中度干旱胁迫下蛋白谱带与第10 d中度干旱胁迫下的蛋白谱带相比,26.4 KD和19.2 KD蛋白谱带增强.这说明干旱诱导了藜一些适应水分胁迫相关基因的表达,或使一些基因的表达量增强,导致一些新蛋白质的出现或某些蛋白质量的增加而增强其对干旱胁迫的抵抗能力.     

苹果链格孢菌侵染对感病苹果品种叶细胞超微结构的影响

 将Alternaria mali分生孢子接种在苹果元帅品种叶片的下表皮,保湿培养3~24h,观察细胞超微结构,接种后3h,表皮及叶肉细胞的质膜发生内陷,出现囊泡,暗染色颗粒及管状结构,叶绿体膜结构解体,电子致密物质沉积,基粒排列混乱松散,外膜破裂等。接种后24h,叶片表面出现病斑,细胞质浓缩,细胞壁出现颗粒物,细胞变形,病健组织交界处,叶绿体基浓缩,出现脂质球,同时还观察到,距离病斑2mm处,许多叶肉细胞中出现密度均匀、形状不规则的物质,小叶脉木质部中出现电子致密物质沉积。     

大豆花叶病毒引发大豆不同症状的生理特性比较

以接种3个SMV株系后分别表现无症状、花叶和坏死症状的大豆品系浙A8901为材料,研究3类症状叶片的生理指标差异,包括细胞超微结构、H_2O_2积累、水杨酸(SA)含量、光合作用及细胞病毒含量。结果表明:无症状叶片细胞中除叶绿体片层结构轻微扭曲外,其它细胞结构未见异常;CeCl_3标记H_2O_2电镜观察,发现H_2O_2仅在细胞壁外侧少量积累;在接种1d后SA含量较对照显著升高。花叶症状叶片细胞中出现髓鞘状结构和多泡体结构,核膜边缘有染色质凝集现象;细胞壁外侧观察到较多H_2O_2的积累;SA含量在接种后第2 d较对照显著增加。坏死症状叶片中细胞变形严重,细胞器解体,在细胞壁外侧和细胞质中均观察到H_2O_2的大量积累;接种后第2 d SA含量较对照显著增加。三类症状叶片的光合速率、最大光能转化效率(Fv/Fm)和实际光量子效率(ΦPSⅡ)的测定发现,与对照相比均无显著变化。     

Fusaproliferin effects on the photosystem in the cells of maize seedling leaves

The possible role of the fusariotoxin, fusaproliferin in plant pathology was investigated with respect to cell membrane potential. Electron microscopy was used to study both the early effect of fusaproliferin on the host’s plasma membrane and ultrastructure responses in the cells of maize leaves. The seedlings of resistant (Lucia) and susceptible (Pavla) to the fusaproliferin maize cultivars were grown in the presence of fusaproliferin at different concentrations, namely 5 and 35 μg ml⁻¹, respectively, and electrophysiological measurements were compared with those obtained using two different toxic compounds, namely fusicoccin and 3-3(3,4 dichlorophenyl)-1,1-dimethylurea (DCMU). It was observed that only the higher concentration of fusaproliferin induced the onset of visible symptoms on the leaves. Comparing the effect of fusaproliferin to that of fusicoccin and DCMU at the higher toxin concentration, it was observed that functional differences in membrane potential induced severe damage to the mesophyll and outer chloroplast membrane; the extent of changes in electrophysiology and ultrastructure disturbances depended on the toxin concentration and was greater in the susceptible cv. Pavla. Results indicated that fusaproliferin could be involved in Fusarium pathogenesis either as a virulence factor or by enhancing the activity of other toxins that might be concomitantly present in infected plants.     

宿根矮化病菌对甘蔗品质及茎、叶超微结构的影响

 甘蔗宿根矮化病(Ratoon Stunting Disease, RSD)是由Leifsonia xyli subsp.xyli (Lxx)引起的,是目前世界所有植蔗地区危害性极大的病害之一。本实验以甘蔗品种新台糖22号(ROC22)健康植株为对照,感染RSD植株为处理,观察和测定RSD侵染甘蔗引起的蔗株农艺性状、蔗糖分以及茎、叶超微结构的变化。结果表明:(1)感染RSD种茎的出苗率比对照减少2.94个百分点;株高比对照下降28.85 cm;茎径比对照减少0.28 cm;节间长度比对照减短3.50 cm;单茎重比对照低0.36 kg。(2)感染RSD植株的蔗糖分低于对照0.9个百分点(绝对值)。(3)利用透射电镜技术对感染RSD植株茎、叶细胞超微结构进行观察表明,叶片叶肉细胞、维管束鞘细胞及茎细胞内的细胞器及细胞核都发生了明显的病理变化。与健康叶片相比,叶绿体变形,叶绿体基质片层大部分消解,基粒结构消失,叶绿体外膜和内膜剥离。线粒体形态异常,有的肿大、内嵴模糊,严重者内嵴消失并空泡化,仅剩未被消解的残骸;细胞核形态变为不规则,核膜破裂,染色质分布不均匀,呈降解状态。在感染RSD甘蔗茎维管束导管细胞内积累有大量的电子致密物质,细胞壁有不同程度的溶解和断裂,这可能和RSD病原细菌侵染有关。以上结果表明:RSD侵染甘蔗后,可能导致光合效率下降,对水分和营养物质的运输能力降低,从而导致甘蔗品质和产量的降低。     

壳寡糖诱导烟草抗烟草花叶病毒的超微结构研究

 电镜检查表明,接种烟草花叶病毒(TMV)表现系统侵染的烟草植株叶肉细胞和筛管内有大量病毒粒子和病毒结晶体,细胞质中出现髓鞘样结构、多泡体和次级囊泡。叶片薄壁细胞内叶绿体、线粒体等细胞器变形解体,膜结构增生。经壳寡糖(50 μg/mL)诱导处理的烟草,系统症状减轻,叶肉细胞和筛管中病毒粒子显著减少,偶见病毒结晶体;叶肉细胞中细胞器基本完好,但叶绿体内出现较大的淀粉粒;液泡内和细胞间隙出现大量电子致密物质。在未接毒和未经壳寡糖处理的植株中未见此种电子致密物,其产生可能与诱导抗病性表达有关。     

低温胁迫下戊唑醇在玉米幼苗体内的残留分析

本试验通过研究低温胁迫下戊唑醇在玉米幼苗植株体内的残留动态,研究发现经试验条件下的低温胁迫(15℃/0℃)处理,其玉米幼苗体内戊唑醇浓度明显高于常温对照(25℃/20℃)的戊唑醇处理,且低温下戊唑醇在玉米幼苗植株中的降解率明显低于常温处理。     

Infection strategy of Ramularia collo‐cygni and development of ramularia leaf spot on barley and alternative graminaceous hosts

Ramularia leaf spot (RLS) is a newly important disease of barley across temperate regions worldwide. Despite this recent change in importance, the infection biology of the causal agent Ramularia collo‐cygni (Rcc) remains poorly understood. Confocal microscopy of the infection process of two transgenic Rcc isolates, expressing either GFP or DsRed reporter markers, was combined with light microscopy during field infection to track the progression of Rcc in planta. Infection of stomata, including the development of a previously unreported stomatopodium structure, results in symptomless development and intercellular colonization of the mesophyll tissue. Transition to necrotrophy is associated with breakdown of host chloroplasts and the formation of aggregates of conidiophores. In addition to barley, Rcc forms a compatible interaction with winter wheat and a number of perennial grass species. An incompatible reaction was observed with two dicotyledonous species. These results provide further insights into the host interactions of this fungus and suggest that RLS could be a potential threat to other agriculturally important crops.     

Viral inclusions in monocotyledons infected by maize streak and related geminiviruses

Isolates of maize streak virus (MSV) were examined by thin-section electron microscopy in plants, assessed for characteristic features of infection and compared with other related geminiviruses infecting monocotyledons from Africa, islands in the Indian Ocean, and the Pacific Island of Vanuatu. Arrays of virus particles, often crystalline, were most often seen in the nucleus. The morphology of the nuclear crystalline arrays was characteristic of certain isolates or groups of isolates (strains). Infected nuclei could be seen in cells from the phloem parenchyma, vascular bundle sheath and mesophyll tissue, and also in epidermal guard cells of plants infected with the maize strain of MSV. The particle arrays varied in morphology from regular rows of virions forming distinctive blocks, to randomly arranged aggregates in certain areas of the nucleus. We consistently failed to find viral crystalline arrays associated with infection of panicum streak virus (PSV) and sugar cane streak virus (SSV) isolates either in these hosts or in maize. Occasionally arrays of MSV particles were found outside the nuclear envelope in physiologically active cells. Accumulations or sheets of MSV particles were seen lining the walls of some phloem companion cells. Crystalline aggregates of particles were frequently observed in the cell vacuole, after lysis of the nuclear membrane of dead cells which made up the chlorotic lesions, the typical symptom of virus infection. Virus preparations from all hosts contained typical geminate particles regardless of the morphology of the virion arrays. The effect on chloroplasts appeared to vary between isolates and this is discussed in relation to lesion colour. The arrangement of virions in the nucleus as a taxonomic character is diagnostic for MSV. Inclusions with crystalline structure found in sieve elements of infected plants were not immunogold labelled when thin sections were probed using antiserum to the virus particles.     

Cassava common mosaic virus infection causes alterations in chloroplast ultrastructure,function, and carbohydrate metabolism of cassava plants

Cassava common mosaic virus (CsCMV) is a potexvirus that causes systemic infections in cassava plants, leading to chlorotic mosaic and producing significant yield losses. To date, the physiological alterations and the mechanism underlying biotic stress during the cassava–CsCMV compatible interaction remains unknown. In this study, we found that CsCMV infection adversely modified chloroplast structure and had functional effects on chloroplasts in source leaves during the course of viral infection. Extrusion of the chloroplast membrane with amoeboid-shaped appearance and disorganized grana stacks were observed in infected mesophyll cells. These alterations were associated with up to 35% reduction of relative chlorophyll content, and a decline of CO₂ fixation (13.5% and 24.2% at 90 and 210 days after planting, respectively). The effects of CsCMV infection on the performance index on absorption basis dropped up to 37%. The analysis of chlorophyll a fluorescence showed a progressive loss of both oxygen evolving complex activity and “connectivity” within the tripartite system (core antenna-LHCII-reaction centre). Here, we report the latter phenomenon for the first time in a viral infection. The oxidative stress process was observed in CsCMV-infected plants (20.8% reduction of antioxidant capacity with respect to noninfected plants). Other effects of the pathogen included reduction of starch and maltose content in source leaves, and a significant increase (24.7%) of the sucrose:starch ratio, which indicates an altered pattern of carbon allocation. Our results suggest that CsCMV induces chloroplast distortion associated with progressive chloroplast function loss and diversion of carbon flux in source leaf tissue, leading to the loss of cassava tuber yield.