The Hypersensitive Reaction in Tobacco Leaf Tissue infiltrated with Pseudomonas pisi 5. Inhibition of RNA Synthesis in Mesophyll Cells

The synthesis of mesophyll cell RNA in tobacco leaf tissue infiltrated with the incompatible bacterium Pseudomonas pisi was investigated by light and electron microscope autoradiography of H³-uridine uptake. Interpretation of the light microscope quantitative data was complicated by the oscillation in levels of cytoplasmic RNA synthesis that resulted from the physical process of fluid infiltration (seen in the control tissue). Direct comparison with the control showed that the presence of bacteria resulted in a rapid decrease in the synthesis of host cell RNA. This effect was clear within the first 1½h (induction period) of the hypersensitive reaction, where it was particularly marked in the cytoplasm of palisade cells. Electron microscope autoradiography showed that the presence of bacteria did not cause complete cessation of RNA synthesis in mitochondria and chloroplasts. The early inhibition of RNA synthesis preceeded fine structural (degenerative) change, and should be regarded as one of the primary events associated with the induction of host cell necrosis.     

Electron Microscope Studies on Pseudomonas syringae pv. phaseolicola Isolated From Inoculated Tobacco Leaves: Changes in Flagellation, Biomass and Elemental Composition During the Hypersensitive Reaction

Cells of Pseudomonas syringae pv. phyaseolicola were infiltrated into tobacco leaves, recovered from tissue macerates at various time intervals during the course of the hypersensitive reaction, then investigated by analytical electron microscopy to determine changes in flagellation, cell size/biomass and elemental composition. In this interaction, the rapid fall in viable count was paralleled by an immediate and progressive decrease in mean cell biomass and a delayed decrease in mean cell size. The percentage occurrence of flagella also showed a sharp fall, suggesting a marked inhibition of bacterial motility. X-ray microanalysis of individual cells in air-dried preparations revealed the routine presence of detectable levels of P, K and Ca throughout the time course. Although signifificant changes in mean mass fractions did occur, the elemental composition of bacterial cells remained relatively stable throughout. The maintenance of substantial levels of K during the hypersensitive reaction suggests that direct damage to bacterial cells, with resulting ion leakage, does not occur.     

The Hypersensitive Reaction of Tobacco to Pseudomonas syringae pv. pisi: Activation of a Plasmalemma K/H Exchange Mechanism

Net electrolyte efflux from suspension-cultured tobacco cells undergoing the hypersensitive reaction to Pseudomonas syringae pv. pisi resulted from a specific efflux of K⁺ which was accompanied by an equimolar net influx of H⁺. These fluxes began 60 to 90 minutes after inoculation of tobacco cells with bacteria, reached maximum rates of 6 to 9 micromoles per gram fresh weight tobacco cells per hour within 2.5 to 3 hours, and dropped below 4 micromoles per gram per hour within 5 hours. Tobacco cells lost approximately 35% of total K⁺ during this period, and average cellular pH declined by approximately 0.75 pH unit. These events were accompanied by a 30% decrease in cellular ATP. K⁺ and H⁺ fluxes were inhibited by the protonophore (p-trifluoromethoxy)carbonyl cyanide phenylhydrazone and by increasing the K⁺ concentration of the external solution. Tobacco leaf discs inoculated with the bacterium also exhibited a specific net K⁺ efflux and H⁺ influx. These results suggest that induction of the hypersensitive reaction in tobacco proceeds through the activation of a passive plasmalemma K⁺/H⁺ exchange mechanism. It is hypothesized that activation of this exchange is a major contributing factor in hypersensitive plant cell death.     

Studies of Small-intestinal Mucosa with the Scanning Electron Microscope

Preliminary observations indicate that scanning electron microscopy is a useful method for studying the surface of the small intestine.     

Electron Microscope Studies on the Absorption and Localization of Lead in the Leaf Tissue 6Potamogeton pectinatus L.

Electron microscope studies have shown that Potamogeton pectinatusL. accumulates lead in the cell walls where it is probably boundaccording to Donnan equilibria. The plasmalemma acts as a barrierto the influx of lead, though pinocytotic invaginations mayconvey some metal into the protoplast and render it non-toxic.With high, toxic lead treatments, deposits were observed inthe cytoplasm and within the chloroplasts. The accumulationof lead in the cell walls and the pinocytotic inclusions, asa feature of lead-tolerant species, is discussed. The data suggesta rapid penetration of ions through the thin cuticle of submergedangiosperms and absorption into the protoplast.     

No Evidence of Direct Superoxide Anion Effect in Hypersensitive Death of Pseudomonas syringae Van Hall in Tobacco Leaf Tissue1

The hypothesis of superoxide anion generation as a direct bactericidal mechanism exercised by hypersensitive tobacco leaf tissue against an incompatible phytopathogenic pseudomonad was tested. The detection of O₂^? was made directly by reducing Cytochrome c and by producing nitrite from hydroxylamine chloride and indirectly by measuring the death of endophytic bacteria in the presence of superoxide dismutase. At 4 h and 6 h the low net specific reduction of Cytochrome c in the hypersensitive tissue was not confirmed by the specific production of nitrite. At the same time active superoxide dismutase did not give significant protection to the incompatible bacteria as compared to inactive superoxide dismutase. The protection provided by active superoxide dismutase as compared with the controls (bovine serum albumine treated tissue and non-treated tissue) at 4 h and at 6 h was not correlated to its superoxide anion scavenger activity. The results indicated that the death of the incompatible pseudomonad during the hypersensitive reaction was not directly linked to O₂^? generation.     

Studies of Opaline Silica Deposits in the Leaf of Sieglingia decumbens L. 'Bernh.', using the Scanning Electron Microscope

Opaline silica deposits (phytoliths) of intracellular originwere photographed at magnifications up to 10⁴ diameters. Becauseof the great depth of focus of the scanning microscope the phytolithswere visible in three-dimensional aspect. They were solid witha possible porous internal structure, and some possessed diagonalstriae on the outer surface. The structural features revealedare related to phytolith models previously postulated from lightmicroscope studies, and to secondary cell-wall structure. Theporous internal structure is discussed in relation to possiblephysico-chemical formative processes.     

紫彩血蛤外套膜的扫描电镜观察

用扫描电镜观察了紫彩血蛤外套膜的表面结构。其内表皮表面具板块状结构 ,沟内和嵴上均有簇生的纤毛丛 ,沟内纤毛丛较多 ;纤毛长约 9μm ,直径约 0 2 μm ,每一纤毛末端具一约 1 μm× 0 6 5 μm的勺状膨大 ;内表皮表面还具丰富的微绒毛和分泌泡。外表皮表面也略呈板块状 ,并有大量分泌泡。     

A Scanning Electron Microscope Study on Gregarina sp. from Udeopsylla nigra*

Scanning electron microscope studies on Gregarina sp. from the cricket Udeopsylla nigra revealed that the epicytic folds of the younger gamonts are undulatory, whereas those of the older gamonts are relatively straight. The protomerite of the primite is conical with a mammiliform structure at the anterior tip, where the epicytic folds originate from a disc-like structure. The protomerite of the satellite is flattened.     

建兰类原球茎体生长、发育过程中扫描电镜观察

建兰(Cymbidium ensifolium)类原球茎体(PLB)培养在含3％蔗糖和不含蔗糖的1/2 MS_0培养基中生长,比较连续光照、8h光照和黑暗条件下原球茎生长发育的动态进程。扫描电镜观察表明:原球茎表面布满密集的发育程度不同的分生区,随继代培养进程,形成分株更多的丛生形原球茎,连续光照促进分生区的增殖,黑暗不利于分生区的发育,在无糖源培养基中生长的PLB,分生区的细胞伸长,发育呈管状结构,这种结构丧失分生能力。在原球茎顶端分化叶原基,并可分化类似气孔的保卫细胞。     

多胞质玉米胚乳淀粉粒性状的扫描电镜观察

１１种多胞质系玉米胚乳淀粉粒的扫描电镜观察表明：不同的细胞质对细胞核有不同程度的互作,３种甜质胞质玉米的胚乳淀粉粒多呈球形,排列紧密,存在一定的共性;４种雄性不育胞质玉米的胚乳淀粉粒多呈不规则形,除（Ｔ）Ｍｏ１７外,排列疏松。这１１种玉米胚乳淀粉粒的平均直径为９．７８μｍ￣１４．６９μｍ,通过玉米胚乳淀粉粒形态特征的观察,在玉米淀粉性状和玉米籽粒的商品价值关系上进行一定程度探索,为玉米的进一步发展     

Scanning Electron Microscope Observation on Endosperm Starch Grain Cnaracters in Orvza sativa subsp. Hsien

Scanning electron microscope observation on the characters of endosperm starch grains of wild rice anti seventeen hsien rice varieties belonging to first and second season cropping indicated that endosperm starch grains of hsien rice generally were polyhedron in sharp and edgy angle indistinct of polyhedron, individual starch grain nearly subrounded in the parts called white belly and white centre. General diameters are in an extent of 3.3–9.3 mm. The shapes of the endosperm starch grains between wild rice and cultivars are similar and sizes leas than hsien rice varieties, but the sizes of the endosperm starch grains of the first eropp4ng axe large than those of the second cropping. The shapes of endosperm starch grains of the varieties to have good exterior quality are polyhedron and structures are arranged closely, Hance, it can be primarily distinguished the good quality of grains from the poor by observation on the endosperm starch grains of varieties.     

蝗虫(直翅目:蝗总科)口器感受器的扫描电镜观察

对蝗总科8种蝗虫的口器感受器的超微结构、类型和分布进行了观察分析,共观察到6种蝗虫口器感受器:毛形感受器、锥形感受器、腔锥形感受器、B(o)hm氏鬃毛、刺形感受器I和刺形感受器Ⅱ,其中B(o)hm氏鬃毛是首次报道.同时对观察到的3种角质齿进行了描述.     

Scanning Electron Microscope Studies of Interactions between Agaricus bisporus (Lang) Sing Hyphae and Bacteria in Casing Soil

Relationships between the hyphae of Agaricus bisporus (Lang) Sing and bacteria from the mushroom bed casing layer were examined with a scanning electron microscope. Hyphae growing in the casing layer differed morphologically from compost-grown hyphae. Whereas the compost contained thin single hyphae surrounded by calcium oxalate crystals, the casing layer contained mainly wide hyphae or mycelial strands without crystals. The bacterial population in the hyphal environment consisted of several types, some attached to the hyphae with filamentlike structures. This attachment may be important in stimulation of pinhead initiation.     

油杉小孢子发生的激光扫描共聚焦显微镜观察

应用激光扫描共聚焦显微镜研究了油杉小孢子的发生过程。油杉样品经曙红-Hoechst 33342双染和冬青油透明后,分别以UV、488 nm激光进行单扫描或系列扫描,并对系列扫描图像进行三维重建。观察结果表明,LSCM图像更能清晰地展示油杉花粉母细胞减数分裂的过程。粗线期染色体密集并缠绕成一团,占据核的一部分,核仁靠在这一团染色体的一边;减数分裂存在扩散双线期;在减数分裂过程中胞质分裂为同时型。观察到中期I、Ⅱ形成的纺锤体和四分体时期胼胝质壁的沉积等。研究结果表明,曙红-Hoechst 33342双染法可用于花粉发育阶段的鉴定,LSCM是研究花粉生物学的理想工具。研究为探究其濒危机制提供有意义资料,为其保护生物学和系统分类学提供胚胎学依据。