缺铁对黄瓜叶肉细胞超微结构及某些形态的影响

利用透射电镜,对缺铁黄瓜幼叶肉细胞的超微结构及植株的某些形态学进行了观测,发现缺铁后的幼叶细胞内首先受到影响的细胞器是叶绿体,其次是线料体,细胞核、内质网结构完好。幼苗缺铁２０天后,大部分叶绿体的基料片层和间质片层受到了严重的破坏。少量线粒体出现空泡化倾向,植株在形态学上表现为幼苗长势衰弱,叶色发黄、叶绿素含量下降     

缺铁对黄瓜叶内细胞超微结构及某些形态的影响

利用透射电镜,对缺铁黄瓜幼叶肉细胞的超微结构及植株的某些形态学进行了观测,发现缺铁后的幼叶细胞内首先受到影响的细胞器是叶绿体,其次是线粒体,细胞核,内质网结构完好,幼苗长势衰弱,叶色发黄,叶绿素含量下降。     

外源色氨酸对海水胁迫长春花幼苗根CCO活性和叶绿体超微结构的影响

以长春花[Catharanthus roseus (L.) G.Don]幼苗为材料,在温室条件下研究了不同浓度色氨酸对20%海水处理14 d后长春花幼苗生长、线粒体细胞色素c氧化酶(CCO)活性、细胞超微结构及长春碱含量的影响.结果显示:(1)与对照相比,20%海水中加入不同浓度的色氨酸,长春花幼苗生长均受到进一步显著抑制,线粒体细胞色素c氧化酶活性下降,但幼苗长春碱含量显著增加.(2) 在20%海水中增加250和500 mg/L色氨酸时,叶绿体片层松散、变稀,色氨酸浓度增大到750 mg/L时,叶绿体变形,片层扭曲、变形,叶绿体模糊、濒临解体.研究表明,在20%海水中增加500 mg/L的色氨酸时,长春花生长受到抑制较小,叶绿体超微结构受损伤程度较轻,而长春碱含量提高幅度最大,从而较有利于长春花幼苗的生长和长春碱的积累.     

锌和铁缺乏对枳生理指标、矿物质含量及叶片超微结构的影响

采用营养液培养法,研究了缺锌(0μmol·L-1 Zn2+)、缺铁(0μmol.L-1 Fe-EDTA)条件下柑橘砧木枳的生理胁迫反应.结果表明:1)锌、铁缺乏使枳生物量与根系活力均显著下降,叶片与根系中的SOD活性明显上升;叶片与根系中的POD活性在缺锌下显著增高,但在缺铁胁迫下显著降低;缺锌处理的根系CAT活性显著上升,但缺铁处理下的CAT活性与对照无显著差异.2)缺铁处理的根部K、Mg、P含量及缺锌处理的地上部K含量均显著降低;缺铁处理的根部和地上部Zn、Cu含量以及缺锌处理的根部Fe、Mn及地上部Mn含量均显著增高.3)叶肉细胞超微结构变化显著,缺铁胁迫下细胞器受损程度较重,如叶绿体、线粒体空泡化严重,叶绿体膜及类囊体片层模糊,质体小球明显增多,无淀粉粒;而缺锌处理时叶绿体基粒片层排列松散、数目明显减少,质体小球明显增多.     

NaCl对小麦幼苗叶肉细胞超微结构的影响

在含NaCl的培养液中培养小麦幼苗,3天后取样观察叶肉细胞,其超微结构基本正常,细胞核和细胞壁没有明显变化。但线粒体结构普遍受到损害,表现在外膜、内膜和嵴膨胀,结构模糊。叶绿体被膜和片层结构仍保持完整,仅有部分叶绿体的片层排列方向发生改变,由原来平行排列扭转为近于垂直排列。     

正丁醇和高光强下转玉米pepc基因水稻叶片超微结构的变化

以高光效高产的转玉米pepc基因水稻(PC)和野生型水稻(WT)为研究材料,在水稻苗期进行高光强处理(120 min,1 000 μmol·m-2·s-1)、高光强正丁醇复合处理(120 min,1 000 μmol·m-2·s-1+0.04%正丁醇)和正常光强处理(200 μmol·m-2·s-1,CK),运用透射电镜观察各处理材料叶肉细胞、维管束鞘、叶绿体、叶绿体片层以及线粒体等结构变化特点,并考察它们叶片的净光合速率(Pn)、磷酸烯醇式丙酮酸羧化酶(PEPC)活性以及收获后的产量构成因子等.结果发现:PC植株具有较高Pn和PEPC活性,与其较高的有效穗数、穗长、千粒重和籽粒产量相对应;与野生型(WT)相比,高光强处理的PC植株叶肉细胞完整,维管束鞘细胞排列整齐,类囊体片层厚,排列有序,堆叠整齐,并且线粒体有序地在叶绿体周围聚集;但经正丁醇和高光强复合处理的PC叶绿体类囊体片层则降解,淀粉粒累积,表现出类似于高光强下WT植株被损坏的超微结构特征.研究表明,转玉米pepc基因水稻叶片的叶肉细胞、叶绿体和线粒体等具有高光效的超微结构特征;PEPC可能通过磷脂酶D(PLD)途径产生的磷脂酸(PA)参与PC在高光强下对类囊体片层稳定性的调节.     

低温胁迫下枇杷幼叶细胞内Ca2+水平及细胞超微结构变化的研究

用焦锑酸钾沉淀的电镜细胞化学方法 ,研究了低温胁迫下枇杷幼叶细胞内 Ca2 水平变化。研究结果表明 ,枇杷幼叶细胞未经低温处理时 ,Ca2 定位分布的沉淀颗粒大量出现在细胞壁、细胞间隙、质膜和液泡 ;叶绿体、细胞质和细胞核中也有一些 Ca2 沉淀颗粒分布。枇杷幼叶经 44h、4℃低温处理后 ,在质膜和液泡膜上 Ca2 的沉淀增多 ,细胞质和细胞核中的Ca2 水平增加。不抗寒品种在低温胁迫条件下可见核孔开口较大 ,有时可观察到核内容物外漏。抗寒品种在低温胁迫条件下核孔未见明显开口 ,叶绿体中类囊体不形成基粒 ,少数片层结合重叠后伸展在整个叶绿体中。而不抗寒品种类囊体则堆积形成明显的颗粒状基粒 ,类囊体片层数量较多。在 2个叶绿体之间还常可见到线粒体紧夹其间 ,但线粒体的内膜模糊不清。不抗寒品种内质网和高尔基体也较多见 ,内膜系统比较发达 ,但低温胁迫条件下膜系统易受破坏 ,膜结构模糊不清。     

短期夜间低温后番茄光合作用及叶绿体超微结构的恢复效应

为明确短期夜间低温后番茄光合作用在常温下的恢复效应,研究了番茄幼苗经夜间15 ℃（对照）、12 ℃、9 ℃和6 ℃处理7 d后植株光合作用和叶绿体超微结构的变化.结果表明：短期夜间低温处理有利于恢复期番茄叶片的光合作用;12 ℃和9 ℃处理叶片叶绿素含量均可恢复至对照水平,6 ℃处理叶绿素含量则不可恢复;夜间低温处理并未严重抑制叶片气孔的形成,相反刺激了恢复期叶片气孔的形成与发育;6 ℃处理后叶绿体基粒片层排列较松散,片层数减少.恢复7 d时,夜间处理温度越低,叶绿体中淀粉粒越小、数量越少,基粒片层排列越整齐致密.另外,短期夜间低温处理促进了番茄植株叶片在恢复期的光合产物运输.     

转PSAG12-ipt基因水稻叶片中叶绿体超微结构的变化

研究了转PSAG12-ipt基因水稻和对照植株发育过程中叶片中的叶绿体结构的变化。发现水稻发育到乳熟期,转基因植株叶片中的叶绿体与对照植株开始出现明显的差别。对照叶绿体中嗜锇体体积增大,数目增多,大部分基粒的类囊体膜膨胀、裂解,片层结构解体。而转基因植株叶片中的叶绿体结构变化不大,嗜锇体相对有所增加,但体积较小,大部分基粒类囊体片层结构仍然排列整齐,少数类囊体垛叠化丧失。     

小麦黄化突变体叶绿体超微结构研究

利用透射电镜对小麦自然黄化突变体及其突变亲本(西农1718)叶片细胞叶绿体的数目、形态及超微结构进行比较分析。结果发现:(1)3种不同黄化程度突变体的叶绿体分布、数目、形状及大小与突变亲本无明显差异;(2)突变体叶绿素含量为野生型58%的黄绿植株与其突变亲本叶绿体超微结构无明显差异,基质类囊体与基粒类囊体高度分化,基粒数目以及基粒片层数目较多;(3)突变体金黄和绿黄植株的叶绿素含量分别为野生型的17%、24%,其叶绿体超微结构与突变亲本明显不同,突变体的叶绿体发育存在明显缺陷,其中突变体金黄植株的叶绿体内无基粒、基质片层清晰可见,有淀粉粒,嗜锇颗粒较多,而突变体绿黄植株的叶绿体内有基粒,但明显少于突变亲本,且基粒片层较少,基质类囊体较发达。结果表明该黄化突变体叶绿体超微结构的改变,是由于叶绿素含量降低造成,推测,该黄化突变是由于叶绿素合成受阻导致的。     

南京老山国家森林公园朴树种群结构与分布格局研究

采用每木调查法、时空互代法和相邻格子样方法对南京老山国家森林公园朴树种群的结构和动态进行研究。(1)大小级结构分析表明:朴树种群以Ⅱ级(幼树)数量最多,Ⅰ级(幼苗)、Ⅲ级(小树)、Ⅳ级(中树)和V级(大树)数量很少或缺失,个别样地内甚至存在2个大小级缺失的情况。朴树种群处于活跃演替阶段的群落中,为不稳定的间歇型种群。(2)对于不同的生境,Ⅰ级数量缺乏甚至缺失基于不同的原因:山坡生境条件下,Ⅰ级缺乏或缺失是由于草本层盖度大,加上朴树幼苗生长缓慢,在激烈的生存竞争中处于不利地位,导致Ⅰ级死亡率高,因而数量较少或缺失;沟谷生境条件下,岩石裸露,土层瘠薄,在雨期受流水冲洗更为严重,影响朴树种子的停留和生根,不合适朴树幼苗生长,导致Ⅰ级缺乏或缺失。(3)生存曲线分析表明:自Ⅱ级向Ⅲ级、Ⅳ级与Ⅴ级的发育过程中,死亡率逐渐降低。(4)朴树的分布格局多为集群分布,在不同生长发育阶段的分布格局不同,朴树种群基本呈现扩散趋势。     

Genetic structure of Pinus brutia stands exposed to wild fires

This study investigates the genetic structure of brutia pine (Pinus brutia Ten.) stands that were exposed to wild fires. A systematic investigation within the species distribution in Greece first identified areas of frequent wild forest fires and then located stands that had experienced ground fires about 20 years ago. In these stands it was possible to sample the pre-fire population that had survived the ground fire event (“mature” population) as well as the post-fire population that has reached reproductive capacity (“young” population). Gel electrophoresis was used in order to study isoenzyme variability in four such populations present in two sites (Kourteri, Lesvos island and Mytilineoi, Samos island). Results indicated absence of notable differences in genetic diversity among the remnant mature populations and the young populations after regeneration. No significant inbreeding was detected and genetic identity among young and mature stands was high. However, some differences were observed in the frequencies of rare alleles and in the presence of interspecific (P. brutia x halepensis) hybrids in the young populations. This paper discusses the above results in the context of the evolution of brutia pine and the maintenance of its genetic variation.     

Humoral immune response of carp Cyprinus carpio to Myxobolus artus (Myxozoa: Myxobolidae) infection

The circulating antibody which reacted with sonicated spores of Myxobolus artus was detected in some naturally infected carp. However, some other fish had no detectable sign of infection, though they had the antibody. When carp were injected either with intact or sonicated spores, the antibody was not produced, while fish injected either with developing stages (presporogonic and sporoblast stages) of the parasite or sonicated spores with bovine serum albumin elicited the antibody production. The results of the injection experiments suggest that (1) developing stages have antigenicity to carp, and (2) spores have lost the antigenicity; sonicated spores are haptens, with which the antibody can react. In an indirect fluorescent antibody technique, sera positive for the antigen reacted with developing stages of the parasite, but not with the spore.
The mechanism of the host immune response against M. artus is discussed in relation to a previous observation that the parasite sometimes underwent abnormal development, in which host encapsulation was imperfect or even lacking, probably leading to degeneration of pseudocysts before the completion of spore formation. It is plausible that the antibody was produced when pseudocysts which showed abnormal growth ruptured during their developing stages, resulting in exposure of the young parasite to the host immune system.     

Combining otolith chemistry and telemetry to assess diadromous migration in pinkeye mullet, <Emphasis Type="Italic">Trachystoma petardi</Emphasis> (Actinopterygii,Mugiliformes)

Little is currently known regarding microbial community structure, and the environmental factors influencing it, within the anchialine ecosystem, defined as near-shore, land-locked water bodies with subsurface connections to the ocean and groundwater aquifer. The Hawaiian Archipelago is home to numerous anchialine habitats, with some on the islands of Maui and Hawaii harboring unique, laminated orange cyanobacterial–bacterial crusts that independently assembled in relatively young basalt fields. Here, benthic and water column bacterial and micro-eukaryotic communities from nine anchialine habitats on Oahu, Maui, and Hawaii were surveyed using high-throughput amplicon sequencing of the V6 (Bacteria-specific) and V9 (Eukarya-biased) hypervariable regions of the 16S- and 18S-rDNA genes, respectively. While benthic communities from habitats with cyanobacterial–bacterial crusts were more similar to each other than to ones lacking it on the same island, each habitat had distinct benthic and water column microbial communities. Analyses of the survey data in the context of environmental factors identified salinity, site, aquifer, and watershed as having the highest explanatory power for the observed variation in microbial diversity and community structure, with lesser drivers being annual rainfall, longitude, ammonium, and dissolved organic carbon. Our results epitomize the abiotic and biotic uniqueness characteristic of individual habitats comprising the Hawaiian anchialine ecosystem.     

Membranous aggregations associated with nuclei inAspergillus flavus hyphae

Summary Different growth regions of young vegetative hyphae ofAspergillus flavus manifested structural modification of certain organelles, especially nuclei. In the apical and subapical zones the interphase nuclei had a normal, non-modified structure. In the region which was a few millimeters distant from the hyphal tip, besides normal nuclei there were some with altered morphology.Such an altered nucleus had electron lucent nuclear content and a membranous aggregate stacked against the nuclear membrane. The aggregate was made of flat, parallel membranes of smooth endoplasmic reticulum (ER). The membranous aggregate was also found in-between two nuclei and the stacking of membranes was highly orderly.     

Passive transfer of respiratory syncytial virus (RSV) antiserum suppresses the immune response to the RSV fusion (F) and large (G) glycoproteins expressed by recombinant vaccinia viruses.

In young infants who possess maternally derived respiratory syncytial virus (RSV) antibodies, the antibody response to RSV glycoproteins is relatively poor, despite extensive replication of RSV. In the present study, it was found that cotton rat RSV hyperimmune antiserum suppressed the antibody response to the RSV glycoproteins but not the response to vaccinia virus antigens when the antiserum was passively transferred to cotton rats prior to infection with vaccinia recombinant viruses expressing the RSV envelope glycoproteins. The cotton rats which had their immune responses suppressed by passively transferred antibodies were more susceptible to infection with RSV than were animals inoculated with control serum lacking RSV antibodies. Furthermore, many of the immunosuppressed animals infected with the vaccinia recombinant viruses developed RSV glycoprotein antibodies which had abnormally low neutralizing activities. Thus, preexisting serum RSV antibodies had dramatic quantitative and qualitative effects on the immune response to RSV glycoproteins, which may explain, in part, the poor RSV antibody response of young human infants to infection with RSV. Our observations also suggest that immunosuppression by preexisting, passively acquired RSV antibodies may constitute a major obstacle to RSV immunoprophylaxis during early infancy, when immunization is most needed.     

Protandric hermaphrodite peculiarities in Amphiprion frenatus Brevoort (Teleostei, Pomacentridae)

Electron microscopy of the male phase of the ovotestis of Amphiprion frenatus , a protandric hermaphrodite, showed no connective tissue between male and female areas and, as the basal lamina was lacking both along the seminiferous tubules and round the previtellogenic oocytes, the male and female germ cells were only separated by their respective surrounding somatic cells (Sertoli and follicle cells). Besides previtellogenic oocytes, oocytes in meiotic prophase and very small (young) previtellogenic oocytes, were detected in the ovarian part, as spermatogenesis proceeded, revealing oogenetic activity. Degeneration of some previtellogenic oocytes and their follicle cells was discernible.     

Maturation of released spores is necessary for acquisition of full spore heat resistance during Bacillus subtilis sporulation

The first ～10% of spores released from sporangia (early spores) during Bacillus subtilis sporulation were isolated, and their properties were compared to those of the total spores produced from the same culture. The early spores had significantly lower resistance to wet heat and hypochlorite than the total spores but identical resistance to dry heat and UV radiation. Early and total spores also had the same levels of core water, dipicolinic acid, and Ca and germinated similarly with several nutrient germinants. The wet heat resistance of the early spores could be increased to that of total spores if early spores were incubated in conditioned sporulation medium for ～24 h at 37°C (maturation), and some hypochlorite resistance was also restored. The maturation of early spores took place in pH 8 buffer with Ca(2+) but was blocked by EDTA; maturation was also seen with early spores of strains lacking the CotE protein or the coat-associated transglutaminase, both of which are needed for normal coat structure. Nonetheless, it appears to be most likely that it is changes in coat structure that are responsible for the increased resistance to wet heat and hypochlorite upon early spore maturation.