摘要:

AbstractIn the green flagellateChlorogonium elongatumthe cAMP concentration of the cells depends on the culture conditions of the alga. Autotrophically cultured cells possess three times more cAMP than cells cultured heterotrophically (in the dark with acetate).The activity of adenylate cyclase in a membrane fraction ofChlorogoniumis distinctly stimulated by GTPγS. Such a stimulation is generally regarded as an indication of the participation of heterotrimeric G‐proteins in this regulatory process.The activity of phosphodiesterase is stimulatedin vitroby calmodulin and inhibited by trifluoperazin and EG

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00319.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe microtubule (Mt) organization in apical cells ofSphacelaria rigidula. as well as in branch initials ofS. rigidulaandEctocarpus siliculosus, was studied by immunofluorescence. The apical interphase cells ofS. rigidulashow an impressive cytoskeleton of Mts, converging on the centrosome(s). A number of Mt bundles are perinuclear, but most of them run in axial orientation from the centrosomes to the cell cortex. The anterior Mt system consists of numerous thin Mt bundles, whereas the posterior system contains fewer and thicker bundles. In cells entering prophase, the cytoplasmic Mts gradually disappear. This process is somewhat faster at the posterior than at the anterior pole of the premitotic nucleus. After mitosis, the cytoplasmic Mts of the apical region appear to be re‐organized more rapidly than those of the basal part of the cell. The apical daughter nucleus retains a lobed shape and condensed chromatin for a longer time, and increases considerably in size between telophase and cytokinesis, compared to the basal one. Duplication of the centrosomes proceeds more rapidly in the anterior region of apical cells than in the basal part. During branch formation inS. rigidulaandE. siliculosus, a new polarity axis is established, and the Mts extend towards the protrusion into which the nucleus migrates before mitosis. After nuclear division, one of the daughter nuclei is positioned at the tip of the branch, where the apical Mt focussing point is localize

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00320.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractInvestigations were carried out to clarify sporopollenin biosynthesis. Tracer experiments were focussed on the incorporation of specifically labeled14C‐phenylalanine into sporopollenin. In addition, the incorporation of further14C‐labeled substances, such as glucose, acetate, malonic acid, mevalonate and tyrosine, was investigated.The sporopollenin fraction was isolated and purified by a gentle method including extractions by different solvents, incubations with hydrolyzing enzymes and fractionated saponifications. During the purification procedure the whereabouts of the initially applied radioactivity was followed. After each step the remaining as well as the released radioactivity was determined. Saponification of samples labeled after application of phenylalanine yielded p‐coumaric acid and p‐coumaric acid methyl ester as labeled products.In comparison with the other substances applied, the highest incorporation rates were obtained with phenylalanine, regardless of the position of labeling. After degradation of the sporopollenin sample labeled with ring‐14C‐phenylalanine, p‐hydroxybenzoic acid was detected as the main labeled product. These results unequivocally show that an integral incorporation of the aromatic ring system occurred.Tracer experiments were carried out at different stages of development. Their results show that, although the incorporation rates of14C‐phenylalanine into sporopollenin differ, the substantial incorporation of this substance is not bound to defined stages

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00321.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractPlants of the annual facultative halophyte and facultative CAM‐plant,Mesembryanthemum crystallinumL., were irrigated with a solution containing NaCl when they had developed 3 leaf pairs. This treatment induced CAM and the plants were then watered with 400 mM NaCl until the end of the experiment of 37 days. A separate set of plants was simultaneously maintained as non‐salt treated controls. Tonoplast vesicles were prepared from the leaves at regular intervals during the time‐course of the experiment. Three samples of each preparation were freezed fractured, and carbon/platinum‐replicas taken. On a total of 1400 fracture faces the diameters and densities per unit area of intramembraneous particles were measured. The results show an increase in the average diameter of particles from 6.5 nm to 8.5 nm and an increase of the relative amount of fracture faces with high particle densities related to the total of fracture faces obtained; both of which kinetically correlated to CAM induction. This increase in size and density of particles, which are known to belong to the H+‐transporting ATPase of the tonoplast. shows independently of and in addition to protein analyses, that an increased amount of ATPase‐protein is incorporated into the membrane during CAM induction. Some possible explanations for the increase in ATPase particle size ar

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00322.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractBafilomycin A1, known as an inhibitor of vacuolar type H+‐ATPase, was used to study involvement of the vacuolar ATP‐dependent H+‐pump in the vacuolar pH regulation in a fresh water charophyte,Chara corallina. When bafilomycin A1(100 nM) was externally given to intact cells, the vacuolar pH (about 5) was not affected. Internodal cells were then pretreated with 100 nM bafilomycin for 1 − 2 h and the vacuolar sap was replaced with a weakly buffered solution of pH 7.4. The readjustment of the modified vacuolar pH in bafilomycin‐treated cells was significantly retarded compared with that in untreated cells.Next, bafilomycin A1was directly introduced into the vacuole by vacuolar perfusion with the artificial cell sap of pH 7.4. At 100 nM bafilomycin A1, the decrease in the vacuolar pH was significantly inhibited. When cell sap was replaced with the artificial cell sap containing no buffer (pH 5.2 − 5.5), the vacuolar pH increased in the presence of vacuolar bafilomycin, suggesting that the PP1‐ dependent H+pumping alone was not sufficient for the pH regulation ofCharavacuoles.Intracellular bafilomycin A1had no effect on the plasma membrane potential of tonoplast‐free cells, which is evidence that it does not affect the electrogenic H+‐pump in the plasma membrane. Bafilomycin A1inhibited the ATP‐dependent H+transport of tonoplast vesicles but not the PP1‐dependent H+transport. The ATPase activity of tonoplast vesicles was also inhibi

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00323.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractRoots ofPinus sylvestrisL. were inoculatedin vitrowith the basidiomyceteSuillus bovinus(Fr.) O. Kuntze. To investigate apoplastic transport in mycorrhizal and sterile roots ofPinus sylvestris, roots of intact plants were submerged for 20 h in 0.1% solutions of the fluorescent dye sulphorhodamine G (SR‐G) or for 6 h in 1.5% solutions of lanthanum nitrate. Samples treated with the dye were cryofixed, freeze‐dried or freeze‐substituted and embedded into Spurr's medium, maintaining strictly anhydrous conditions to prevent movement of the water‐soluble dye after cryofixation. Lanthanum‐treated roots were fixed in glutaraldehyde, post‐fixed in OsO4, dehydrated in a graded acetone series and embedded in Spurr's resin. The apoplastic distribution of the two tracers were examined either using fluorescence optics (sulphorhodamine) or with the electron microscope (La3+).The yellow‐green fluorescence of sulphorhodamine could be detected within the apoplast of the fungal sheath, the Hartig net and the host cortex, up to the endodermis. Electron‐dense lanthanum deposits were located in the fungal sheath, the Hartig net and in the root cortex. Greater deposition was detected within the matrix material, in which the hyphae of the mantle are embedded. The apoplastic distribution of the two tracers within the plant root did not indicate any significant qualitative differences between sterile and mycorrhizal rootlets. In contrast to reports by other authors, we conclude that the fungal sheath does provide an apoplastic pathway for water and ions at least inPinus sylvestris/Suillus bovinusmycorrhizae. However, the mobility of charged molecules, particularly cations, may be limited by th

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00324.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe UV light (337 nm) induced blue‐green fluorescence emission of green leaves is characterized at room temperature (298 K) by a maximum near 450 nm (blue region) and a shoulder near 525 nm (green region) and was here also studied at 77 K. At liquid nitrogen temperature (77 K) the blue (F450) and green fluorescence (F525) are much enhanced as is the red chlorophyll fluorescence near 735 nm. During development of green tobacco leaves the blue fluorescence F450 (77 K) is shifted towards longer wavelengths from about 410 nm to 450 nm. The isolated leaf epidermis of tobacco showed only slight fluorescence emission with a maximum near 410 nm. The green fluorescence F525 was found to mainly originate from the mesophyll of the leaf, its intensity increased when the epidermis was removed. The red chlorophyll fluorescence emission was also enhanced when the epidermis was stripped off; this considerably changed the blue/red fluorescence ratios F450/F690 and F450/F735. The epidermis, with its cell wall and UV‐light‐absorbing substances in its vacuole, plays the role of a barrier for the exciting UV‐light. In contrast to intact and homogenized leaves, isolated intact chloroplasts and thylakoid membranes did not exhibit a blue‐green fluorescence

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00325.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAction spectra of photogravitropic equilibrium were measured for the wild type of the lower fungusPhycomyces blakesleeanusand three photobehavioral mutants with defects in themadlgene. The action spectrum for the wild type NRRL1555 had major peaks at 383 and near 460 nm and subsidiary peaks at 365 and 422 nm. The action spectra of the mutants, L1 49mad1712, L151mad1714and L153mad1716differed significantly from that of the wild type. One prominent feature of the three mutants was hat the near‐UV peaks at 365 and 383 nm, which were not well resolved in the wild type, were of approximately equal height in the mutants and were separated by an extremely sharp valley at 378 nm. The steepness of this valley suggests interaction of multiple receptors. The second prominent feature of the mutants was their enhanced 422 nm peak. The gross changes of the photogravitropic action spectra associated with themadlgenotype indicate that the respective gene product acts early in the photosensory transduction chain, very likely at the level of a complex photoreceptor system. Flavins and pterins, two pigment classes which were expected to function as chromophores of the near‐UV/blue light photoreceptor system, were analyzed for stage I sporangiophores of the wild‐type and the mutant strains by HPLC with fluorescence detection. In the wild‐type strain NRRL1555, and also in the threemadlmutants, flavins were found to be present at the following concentrations: riboflavin (2.9 × 10−6M), FMN (3.8 × 10−6M) and FAD (1.3 × 10−6M). No significant effect of themadlmutations on the flavin content could be discerned. Among the pterins found in the wild type and themadlmutants were biopterin, 6,7‐dimethylpterin, neopterin, pterin and xanthopterin. These pterins occurred in all strains in the micromolar range and none of them was significantly reduced in the mutants. However, biopterin, 6,7‐dimethylpterin and xanthopterin occurred in some excess in one of themadlmutants. The most significant feature of themadlmutants was that they had almost completely lost one unidentified pterin with a retention time of 18 − 20 min. Another two unidentified pterins were reduced about twofold in the mutants compared to the wild type. The results suggest an involvement of pterins in the photoreception of near‐UV and

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00326.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis work describes the rhizomorphs and their relation to thallus development in the squamulose lichenAspicilia crespianaRicoined. The rhizomorphs capture algal cells, giving rise to new squamules terminally or laterally. The thallus thus consists of a network of lichenized squamules interlinked by mycobiontic rhizomorphs. A previously proposed comparison of lichen rhizomorphs to the prothallus (hypothallus) of crustose lichens is applied and expanded upon. Other less organized prothallic structures sometimes produced byA. crespianaare also described. The importance of lichenizing rhizomorphs as an essential feature of thallus growth in this species is emphasized and a competitive role in substrate occupation and thallus expansion is suggested.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00327.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAustropeltumgen. nov. is described as a monotypic genus of the family Stereocaulaceae. It differs from other genera of the family by a sqamulose habit. The single species,Austropeltum glareosumsp. nov. is characterized by an heteromerous thallus with a thick, heavily gelatinized upper cortex, and stalked, lecideine, glomerate apothecia. The apothecial stalk is a pseudopodetium, which is delimited from the subhymenium by a pigmented boundary tissue. Asci are eight‐spored and possess an amyloid tube‐structure; the simple ascospores are fusiform and colourless. Filiform conidia are produced laterally and terminally in marginal pycnidia.A. glareosumgrows over gritty soil on exposed mountain summits and plateaux in New Zealand and Tasma

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00328.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY