施肥对烟草腺毛叶绿体形态结构的影响

以烤烟K326为材料,在盆栽条件下分别施用纯有机肥和无机肥,在烟株旺长期和成熟期对叶面腺毛进行显微和超微结构观察,以明确肥料对烟草叶面腺毛生长发育的影响,结果显示:移栽后50 d,荧光下观察有机肥处理下腺头细胞叶绿素荧光强度较无机肥强烈,腺头细胞内叶绿体结构完整,类囊体基粒片层发达,嗜锇颗粒大而多;无机肥处理的细胞内叶绿体少,嗜锇颗粒较小,数量也较少.移栽后70 d,有机肥处理腺毛头细胞叶绿体双层膜结构依然完整,但类囊体基粒片层结构已经解体,其中积累大量黑色嗜锇颗粒;此时无机肥处理腺毛头细胞叶绿体结构完整,仍可清晰看到类囊体基粒片层仅含少量嗜锇颗粒.推测有机肥处理在初期促进了烟草腺毛细胞叶绿体的发育和叶绿素的合成、积累,在后期,促进叶绿素及内膜系统的降解,并有利于亲脂类物质的合成和积累,从而对腺毛分泌物积累和烟叶香气品质形成具有积极影响.     

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。     

白粉菌侵染对小麦叶片显微及超微结构的影响白粉菌侵染对小麦叶片显微及超微结构的影响

通过半薄及超薄切片,比较了正常和受白粉菌感染的小麦叶片细胞的显微及超微结构的差异。观察结果发现(1)受感染小麦叶肉细胞的细胞壁上局部沉积大量团状电子致密颗粒;(2)叶绿体形状由原来的椭圆形转变成圆形,叶绿体膜破裂,类囊体膨大,基粒片层排列疏松,同时,叶绿体内嗜锇性颗粒数量增加;(3)线粒体膜解体,内含物分散到了细胞质中     

龙葵腺毛发育的细胞学研究

利用光学显微镜、扫描电镜和透射电镜技术,观察了龙葵“四叶一心”期时叶片及茎表皮的腺毛的种类、分布,探究了不同类型腺毛的起源、生长、成熟、分泌、衰老等发育过程的细胞学特征;通过组织化学染色和荧光显微技术,观察了龙葵腺毛成分、分布,为龙葵的进一步开发利用提供参考。结果表明：（1）龙葵腺毛分为单细胞头腺毛和多细胞头腺毛两类,前者主要分布于茎表面和叶上下表皮,后者主要分布于茎表面的单细胞头腺毛之间、叶脉及叶边缘;（2）龙葵腺毛发育起始于表皮细胞突起,单细胞头腺毛行顶端生长,具1-4个柄细胞,四种类型;多细胞头腺毛可再分为一层、两层与三层多细胞头腺毛,另具三种特殊类型;（3）龙葵成熟腺毛具分泌能力,通过皮下空间的物质积累导致腺毛头细胞表面形成突起、包块、破口,最终释放分泌物;而头细胞与柄细胞随即皱缩、衰老。（4）超微结构显示,腺毛头细胞中内质网与高尔基体极为丰富,合成代谢及分泌活动活跃,产生大量包裹嗜锇物质的囊泡,囊泡与细胞壁融合,进而将嗜锇物质转移至细胞壁并积累,随后储存在角质层下的皮下空间直至分泌释放;（5）组织化学染色结果表明,腺毛含有萜类、生物碱、脂类、蛋白质、酚类和多糖。头细胞中主要含有萜类、生物碱、脂类、蛋白质、酚类和中性多糖;柄细胞中主要含有萜类、生物碱、脂类。     

菊花黄绿叶突变体不同类型叶片的叶绿素含量和结构特征比较

以菊花黄绿叶突变体-NAu04-1-31为试验材料,测定了黄叶、黄绿叶和绿叶3种不同类型叶片的叶绿素含量,并观察比较了叶片的显微与超微解剖结构.叶绿素含量测定表明:黄叶、黄绿叶的叶绿素含量显著低于绿叶,而黄叶叶绿素a与叶绿素b的比值大于绿叶.叶绿体显微与超微结构观察发现:黄叶细胞内叶绿体形状不规1则,缺乏正常的叶绿体膜结构,无类囊体,无淀粉粒,嗜锇颗粒较多;黄绿叶叶片栅栏组织绿色部分与绿叶的栅栏组织相似,黄色部分与黄叶的栅栏组织棚似,黄色部分的海绵组织中有类似于绿色叶片的海绵组织结构,而绿色部分含有类似于黄叶的海绵组织的结构特征.绿叶细胞内叶绿体较多,形状规则,基粒片层清晰,其内淀粉粒多而大,嗜锇颗粒较少.     

银杏叶发育过程的解剖结构观察

利用半薄切片、扫描电镜和透射电镜技术,对不同发育时期的银杏叶片解剖结构变化进行连续观察.结果显示:(1)展叶期叶片无栅栏组织和海绵组织分化,细胞排列紧密;展叶后叶肉分化为栅栏组织1~2层,细胞呈长椭球形,海绵组织发达,细胞呈横向排列的椭球形,并形成通气系统;衰老期部分海绵组织细胞变小,并纵向排列,通气系统发达.(2)除叶基和叶缘外,成熟叶片的维管束直径基本相同,维管束鞘发达.(3)早期叶片上表皮有较多气孔分布,展叶后气孔密度迅速降低;下表皮气孔数量较多,但气孔密度随叶片的成熟逐渐下降.(4)叶绿体类囊体在展叶期结构简单,常含1~2个较大淀粉粒;生长期类囊体结构逐渐完善,淀粉粒较少,无嗜锇滴;衰老期类囊体瓦解,嗜锇滴大量累积.     

NaCl胁迫对5个引自北美的树种叶肉细胞超微结构的影响

为明确美国白蜡(Fraxinus americana L.)、茶条槭(Aceginnala Maxim.)、红桤木(Alnus rubra Bong.)、水紫树(Nyssa aquatica L.)和美国皂荚(Gleditsia triacanthos L.)5个引自北美的树种的耐盐性,采用水培方法、利用透射电镜技术对0(对照)、4和8 g·L-1 NaCl胁迫处理后5个树种1年生苗叶肉细胞超微结构的变化进行了观察和比较.观察结果表明:正常条件(0g·L-1NaCl)下,5个树种叶肉细胞在叶绿体形态、嗜锇颗粒数量等方面略有差异,但均未发生质壁分离现象.经NaCl胁迫处理后,5个树种叶肉细胞中的叶绿体和细胞核受到不同程度的损伤,表现为叶绿体膜消失,类囊体片层结构肿胀,叶绿体降解,嗜锇颗粒增大或增多,细胞核的核膜消失、核染色质凝聚;且随NaCl质量浓度的提高,损伤程度均逐渐加剧.4和8g·L-1NaC1胁迫条件下,美国皂荚、茶条槭和水紫树的叶肉细胞发生质壁分离现象,而红桤木、美国白蜡和水紫树的叶肉细胞内出现环状片层.根据观察结果,推测红桤木和美国白蜡对NaCl胁迫的耐性较强,美国皂荚和茶条槭也有一定的耐性,而水紫树的耐性最弱.     

白粉菌侵染对小麦叶片显微及超微结构的影响

通过半薄及超薄切片,比较了正常和受白粉菌感染的小麦叶片细胞的显微及超微结构的差异。观察结果发现：（1）受感染小麦叶肉细胞的细胞壁上局部沉积大量团状电子致密颗粒;（2）叶绿体形状由原来的椭圆形转变成圆形,叶绿体膜破裂;类囊体膨大,基粒片层排列疏松,同时,叶绿体内嗜饿性颗粒数量增加;（3）线粒体膜解体,内含物分散到了细胞质中。     

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。     

发菜的显微及亚显微结构的观察

通过光学显微镜、扫描电镜和透射电镜的观察、了解到一条发菜原植体大约由数十万计的念珠状细胞所组成,其藻丝多为单链,但也发现有分枝现象。整个原植体包被着厚薄不均的胶质鞘,外观粗糙,沟稜状起伏,且多裂隙。念珠状细胞为典型的原核细胞。细胞壁有三层结构,中央为色浅的核质区,四周为细胞质区其中散布着大量膜层薄而散乱的类囊体,膜上附有大量 rRNA 和藻胆体颗粒。还发现有膜层密集形如指纹的小类囊体。在细胞质中还分布着结构颗粒,多角体、聚磷酸体等嗜锇物质结构.一般细胞都具有分裂能力,方式多为横缢,先是细胞壁逐渐向中央扩展,最后将母细胞分成两个子细胞.从异形胞的结构特征来看,主要功能是渡过恶劣环境以保存物种。     

定位于类囊体膜的PPF1在转基因拟南芥中的表达影响叶绿体的发育

PPF1是一个与植物营养生长相关的基因。它编码的产物可能是一个膜蛋白并与拟南芥叶绿体中的类囊体蛋白ALB3有很高的同源性。免疫电镜分析表明PPF1蛋白同样主要定位于类囊体膜 ,而且在短日照G2豌豆开花两周后仍发育良好的叶绿体中有很高的表达 ,在长日照豌豆同时期非正常叶绿体中丰度非常低。对转基因拟南芥和野生型植株的叶片衰老进程比较发现 ,PPF1在拟南芥中的过量表达可以延缓叶片的衰老 ,而用PPF1反义mRNA抑制拟南芥中的同源基因ALB3则明显加快叶片衰老速度。对转基因拟南芥的超微结构分析显示 ,PPF1在拟南芥中过量表达时 ,转基因植株的叶绿体比野生型植株的叶绿体大并含有更多的基粒和基质类囊体膜 ;相反 ,反义PPF1表达抑制其在拟南芥中的同源物时 ,转基因植株的叶绿体比野生型植株的叶绿体小并含有较少的基粒和发育较差的类囊体膜系统。这些数据表明叶绿体的发育状况与PPF1或拟南芥同源物ALB3的表达水平呈正相关。我们的结果提示PPF1基因可能通过控制叶绿体的发育状况来调节植物的发育。     

Leaf morphological and ultrastructural performance of eggplant (Solanum melongena L.) in response to water stress

The effects of water stress on leaf surface morphology (stomatal density, size, and trichome density of both adaxial and abaxial surfaces) and leaf ultrastructure (chloroplasts, mitochondria, and cell nuclei) of eggplant (Solanum melongena L.) were investigated in this study. Higher stomata and trichome densities were observed on abaxial surface compared with the adaxial surface. Compared with well watered (WW) plants, the stomata and trichome density of the abaxial surface increased by 20.39% and 26.23% under water-stress condition, respectively. The number of chloroplasts per cell profile was lesser, the chloroplasts became round in a shape with more damaged structure of membranes, the number of osmiophilic granules increased, and the number of starch grains decreased. The cristae in mitochondria were disintegrated. The cell nuclei were smaller and the agglomerated nucleoli were bigger than those of WW plants. Our results indicated that the morphological and anatomical responses enhanced the capability of plants to survive and grow during stress periods.     

3-D modelling of chloroplast structure under (Mg) magnesium ion treatment. Relationship between thylakoid membrane arrangement and stacking

We performed for the first time three-dimensional (3D) modelling of the entire chloroplast structure. Stacks of optical slices obtained by confocal laser scanning microscope (CLSM) provided a basis for construction of 3D images of individual chloroplasts. We selected pea (Pisum sativum) and bean (Phaseolus vulgaris) chloroplasts since we found that they differ in thylakoid organization. Pea chloroplasts contain large distinctly separated appressed domains while less distinguished appressed regions are present in bean chloroplasts. Different magnesium ion treatments were used to study thylakoid membrane stacking and arrangement. In pea chloroplasts, as demonstrated by 3D modelling, the increase of magnesium ion concentration changed the degree of membrane appression from wrinkled continuous surface to many distinguished stacked areas and significant increase of the inter-grana area. On the other hand 3D models of bean chloroplasts exhibited similar but less pronounced tendencies towards formation of appressed regions. Additionally, we studied arrangements of thylakoid membranes and chlorophyll-protein complexes by various spectroscopic methods, Fourier-transform infrared spectroscopy (FTIR) among others. Based on microscopic and spectroscopic data we suggested that the range of chloroplast structure alterations under magnesium ions treatment is a consequence of the arrangement of supercomplexes. Moreover, we showed that stacking processes always affect the structural changes of chloroplast as a whole.     

Deletion of the chloroplast-localized AtTerC gene product in Arabidopsis thaliana leads to loss of the thylakoid membrane and to seedling lethality

Early seedling development in plants depends on the biogenesis of chloroplasts from proplastids, accompanied by the formation of thylakoid membranes. An Arabidopsis thaliana gene, AtTerC , whose gene product shares sequence similarity with bacterial tellurite resistance C (TerC), is shown to be involved in a critical step required for the normal organization of prothylakoids and transition into mature thylakoid stacks. The AtTerC gene encodes an integral membrane protein, which contains eight putative transmembrane helices, localized in the thylakoid of the chloroplast, as shown by localization of an AtTerC–GFP fusion product in protoplasts and by immunoblot analysis of subfractions of chloroplasts. T-DNA insertional mutation of AtTerC resulted in a pigment-deficient and seedling-lethal phenotype under normal light conditions. Transmission electron microscopic analysis revealed that mutant etioplasts had normal prolamellar bodies (PLBs), although the prothylakoids had ring-like shapes surrounding the PLBs. In addition, the ultrastructures of mutant chloroplasts lacked thylakoids, did not have grana stacks, and showed numerous globular structures of varying sizes. Also, the accumulation of thylakoid membrane proteins was severely defective in this mutant. These results suggest that the AtTerC protein plays a crucial role in prothylakoid membrane biogenesis and thylakoid formation in early chloroplast development.     

Chloroplast biogenesis. Regulation of lipid transport to the thylakoid in chloroplasts isolated from expanding and fully expanded leaves of pea

To study the regulation of lipid transport from the chloroplast envelope to the thylakoid, intact chloroplasts, isolated from fully expanded or still-expanding pea (Pisum sativum) leaves, were incubated with radiolabeled lipid precursors and thylakoid membranes subsequently were isolated. Incubation with UDP[(3)H]Gal labeled monogalactosyldiacylglycerol in both envelope membranes and digalactosyldiacylglycerol in the outer chloroplast envelope. Galactolipid synthesis increased with incubation temperature. Transport to the thylakoid was slow below 12 degrees C, and exhibited a temperature dependency closely resembling that for the previously reported appearance and disappearance of vesicles in the stroma (D.J. Morré, G. Selldén, C. Sundqvist, A.S. Sandelius [1991] Plant Physiol 97: 1558-1564). In mature chloroplasts, monogalactosyldiacylglycerol transport to the thylakoid was up to three times higher than digalactosyldiacylglycerol transport, whereas the difference was markedly lower in developing chloroplasts. Incubation of chloroplasts with [(14)C]acyl-coenzyme A labeled phosphatidylcholine (PC) and free fatty acids in the inner envelope membrane and phosphatidylglycerol at the chloroplast surface. PC and phosphatidylglycerol were preferentially transported to the thylakoid. Analysis of lipid composition revealed that the thylakoid contained approximately 20% of the chloroplast PC. Our results demonstrate that lipids synthesized at the chloroplast surface as well as in the inner envelope membrane are transported to the thylakoid and that lipid sorting is involved in the process. Furthermore, the results also indicate that more than one pathway exists for galactolipid transfer from the chloroplast envelope to the thylakoid.     

Studies on the Conversion of Chloroplast to Chromoplast During Fruit Ripening in Solanum pseudo-capsicum var. diflorum

Determination of chlorophyll and carotenoid contents in the ectocarp during fruit ripening in Solanum pseudo-capsicum var. diflorurn (Veil.) Bitter revealed that the changes of fruit colour coincided with the decline of chlorophyll and the increase of carotenoid contents. The conversion of chloroplasts to chromoplasts in the fruit was studied by electron microscopy. The early green fruit was characterized by chloroplasts with a typical grana-intergranal thylakoid structure. At yellow-green fruit stage the thylakoid system was disintegrated and replaced by few non-chlorophyllous single thylakoids, with accumulation of large osmiophilic plastoglobules. The plastids developed as the so-called proplastids. These indicated dedifferentiation of chloroplasts in a ripening fruit. When the fruit reached its yellow stage, numerous large plastoglobules contained in the young chromoplasts frequently showed transitional changes to plastid tubule structure. At first, the center of plastoglobules became semi-translucent. It was believed that the young chromoplast were in an initial state of carotenoid deposition, followed by plastoglobules elongation and tubule protrution from the globules. These tubules were surrounded with an electron dense membranous sheath leaving the core semi-translucent. Concurrently a series of vesicles in different developmental stages appeared from the stroma of the plastid, likely representing a process of formation of numerous small new plastoglobules. In the chromoplasts of a ripe orange-or orange red-colored fruit only numerous tubules and small plastoglobules were present. The plastid tubules increased in number and elongated in length filling the mature chromoplast. Numerous small plastoglobules also increased and distributed in the spaces between tubules. These results indicated that the reconstruction of a mature chromoplast from a dedifferentiated plastid was really a form of redifferentiation, and it might be concluded that the conversion of chloroplast to chromoplast in the fruit of S. pseudo-capsicum var. diflorum, in fact, was a processes of dedifferentiation and redifferentiation.     

Paraquat tolerant and susceptible perennial ryegrasses: effects of paraquat treatment on carbon dioxide uptake and ultrastructure of photosynthetic cells

Abstract. Paraquat treatment of susceptible Lolium perenne seedlings (cultivar Kent Indigenous) rapidly inhibited CO₂ uptake and after 1 h chloroplasts exhibited abnormal fusions of the thylakoid membranes. Further ultrastructural changes occurred within the chloroplasts until 8 h after treatment, when cytoplasmic damage also became evident. The localization of primary damage within the chloroplast differs from previous reports of paraquat toxicity in other species. Paraquat treatment of tolerant L. perenne seedlings (line PRP IX) resulted in little change in CO₂ uptake and ultrastructural effects were generally confined to the gradual development of deposits in the chloroplast stroma. These observations are discussed in relation to the mechanism of action of the herbicide and the proposed mechanism of paraquat tolerance in L. perenne.     

ULTRASTRUCTURAL CHANGES OF CHLOROPLASTS IN ATTACHED AND DETACHED,AGING PRIMARY WHEAT LEAVES

Degradation of chloroplasts is shown in mesophyll cells of primary leaves of wheat. The sequence of ultrastructural changes in chloroplasts of naturally senescing leaves is compared with that of detached, aging leaves. In chloroplasts of naturally senescing leaves, the first indications of aging are the appearance of osmiophilic globuli and reorientation of the thylakoidal system. The membranes of the grana and intergrana lamellae then become distended and later dissociate into distinct vesicles. Concurrent with these membrane changes, osmiophilic globuli increase in size and number, and the stroma breaks down. Finally, the chloroplast envelope ruptures and plastid contents disperse throughout the cell's interior. In chloroplasts of mesophyll cells in detached, aging leaves, initial changes also include appearance of osmiophilic globuli, but later stages of chloroplast degradation are different. The chloroplast envelope ruptures before the lamellae break down. Swelling of grana and intergrana lamellae is not pronounced and, additionally, the thylakoidal system degenerates without forming vesicles or numerous osmiophilic globuli. These differences in the sequence of chloroplast degradation indicate that naturally senescing leaves rather than detached, aging leaves should be used in studies of chloroplast senescence.