ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractConcanamycin 4‐B, a macrolide antibiotic with an 18‐membered lactone ring, is known as a specific inhibitor of the vacuolar type of H+‐ATPase, as is bafilomycin A1. The drug was tested for its effect on regulation of the vacuolar pH (pHv) of internodal cells of a fresh water characean alga,Chara corallina, under normal conditions and under salt stress. The pHvwas measured either on isolated vacuolar sap with a conventional pH electrode or directly by inserting a pH‐sensitive glass microelectrode into the vacuole. Proton‐pumping into tonoplast vesicles was almost completely inhibited by concanamycin 4‐B at 1 nM.Concanamycin 4‐B at 1 μM significantly increased pHvwhile bafilomycin A1was ineffective when applied at 1 μM. Concanamycin 4‐B did not affect pHvwhen applied at 0.1 μM and increasing the concentration to 10 μM did not amplify the degree of alkalization.Concanamycin 4‐B also inhibited pHvregulation under NaCl stress. WhenCharacells were treated with 100 mM NaCl, pHvpromptly increased and then recovered to the original level. The reacidification was completely inhibited by concanamycin 4‐B (1 μM), suggesting that the reacidification was achieved by the H+

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of ABA on intracellular pH, net H+extrusion, Cl−fluxes and Emvalues were studied inElodea densaleaves, and the possible relationships between the ABA‐induced changes of cytosolic pH and of Cl−and H+fluxes were investigated. Cytosolic and vacuolar pH were calculated by the weak acid and weak base distribution method. The data show that, also in this material (a water plant without stomata), ABA induces a decrease in both net H+extrusion and intracellular pH, and strongly inhibits Cl−efflux. No significant effect of ABA is detectable on Emvalues, either at short or long intervals in the presence or absence of K+. Cl−efflux is apparently independent of the activity of the plasmalemma H+pump and of the Emvalues. Conversely, it strongly depends on the value of cytosolic pH, a larger efflux occurring for the lower pH values both in the presence and in the absence of ABA. These results indicate that the ABA‐induced cytosolic acidification cannot be the cause but, possibly, a consequence of the decrease in Cl−efflux, and are consistent with the hypothesis of a primary role of ABA in regulating Cl−efflux, presumably by directly affecting a class of Cl−

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWhen grown heterotrophically in the dark on enriched culture medium, the pigment‐deficient strain ofScenedesmus obliquus, mutant C‐6E, is uniquely characterized by a complete deficiency in carotenoids and chlorophyllbwhile retaining a low level of chlorophyllawhich is exclusively utilized in photosystem I‐type reactions. The strain lacks photosystem II activity but exhibits all PS‐I reactions tested, including P700 redox reactions, photoreduction of CO2with hydrogen as electron donor, and O2uptake following methyl viologen reduction. The mutant contains 10 times more P700 per chlorophyll than the wild type and develops the pigment‐protein complex of PS‐I, CP‐I. The action spectrum for methyl viologen reduction compares favorable to the low temperature absorption spectrum of whole cells. Both the chlorophyll fluorescence excitation and emission spectra of pigment‐protein complexes derived from cells of C‐6E show patterns typical of PS‐I. The strain lacks the LHCs and CP‐II as well as their respective apoproteins. The absence of carotenoids appears to prevent the development of the normal variety of pigment‐protein complexes and the accumulation of Chlb. This inability is also expressed by the presence of only single stranded thylakoid membranes in the chloroplast of C‐6E. When heterotrophically grown cells of this mutant are exposed to white light of 8 or 22 W m−2, 50% of its chlorophyll is lost by photooxidation within 4

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in two N2‐fixing cyanobacteria,Anabaenasp. andNostoc carmium, isolated from rice paddy fields in India. Phycobiliproteins were isolated and separated by sucrose density gradient centrifugation. After UV exposure the top fraction mainly contained carotenoids (absorption maximum at 485 nm), which first showed an increase in intensity and absorption and then a gradual decrease with increasing UV exposure inAnabaenasp., whereas, inNostoc carmiumthis fraction showed a steady increase over the whole exposure time. The bottom fraction of both organisms mainly contained phycocyanin (absorption peak at 620 nm) which showed a steady decline in intensity, as well as absorption. Fluorescence excitation at 620 nm resulted in an emission at 650 nm which underwent a shift towards shorter wave‐lengths with increasing UV‐exposure time, indicating a disassembly of the phycobilisomal complex and of impaired energy transfer from accessory pigments to the reaction centers. SDS PAGE analysis of the fractions revealed a loss of high molecular mass linker proteins and low molecular mass (αβ monomers indicating that the phycobiliproteins, which function as accessory pigments for the operation of photosystem II, disassemble during UV ir

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSynthesis of stress proteins after heat shock and different periods of UV‐B radiation were investigated with marine diatom species from the North SeaDitylum brightwellii, Lithodesmium variabile, Odontella sinensis, Thalassiosira rotulaand the Antarctic diatomOdontella weissfloggiifrom the Weddell Sea. Algae were grown in an artifical sea‐water medium under controlled laboratory conditions: light/dark regime of 12:12 h (7.2 W m−2), normal air (0.035 vol.% CO2) and 18° or 4 °C. All the tested diatom species can produce heat shock proteins (HSPS) of the 70 kDa family byin vivolabelling with [35S]‐methionine. The same results were obtained forOdontella sinensis, Ditylum brightwelliiandOdontella weissflogiiby estimation of thein vitrotranslation products with poly‐A‐mRNA isolated from these organisms. However,Odontella weissflogii, a species relatively insensitive to UV‐B irradiance, did not synthesize UV‐induced HSPS, whereas the UV‐sensitive diatomOdontella sinensis, as well asLithodesmium variabile, produced all the observed HSPS after UV‐B exposure. In addition, a protein of 43 kDa was found after UV‐B irradiance of the temperateOdontella sinensis. The temperate marine diatomThalassiosira rotulasynthesized 70 kDa and 5 7 kDa proteins after a heat shock and a UV‐B exposure of 2 h, but a 40 kDa protein could not be detected, whereas a 60 kDa protein was found after 2 h UV‐B exposure. The results are discussed in view of a possible adaptation ofO. weissf

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPhotoinhibition of photosynthesis in the brown alga,Dictyota dichotoma, was studied with a PAM fluorometer (Walz, Effeltrich, Germany) and a homemade oxygen measuring device. As a measure of fluorescence, Fv/Fm, and for the photosynthetic yield, ΔF/Fm', were used. Oxygen measurements show clearly that the observed degree, as well as the time course, of photoinhibition depends on the fluence rate of the light used to measure changes of the production rate. After photoinhibition of photosynthesis the depression of oxygen production caused by non‐saturating fluence rates was generally much more pronounced than that caused by saturating or nearly saturating fluence rates. At minimal photoinhibition the initial slope and the convexity of the fluence rate‐response curve of oxygen evolution decrease, whereas the level of light saturation decreases only after strong photoinhibition. Nevertheless, at different degrees of photoinhibition, changes in the degree of the upper bending of the fluence rate‐response curve of oxygen production are also linearly correlated to changes in the fluorescence ratios (Fv/Fm and ΔF/Fm'). The action spectrum of photoinhibition, calculated on the basis of changes of Fv/Fm, indicates that the reaction center of PS I is not involved in photoinhibition. The lower effectiveness of blue light in comparison to effects of green and red light may be due to chloroplast displacement, as in the so‐called strong light position, the light absorbed by the thalliin vivois

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00838.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractRelative growth rate of winter wheat at low temperature (day/night, 4/2 °C) was about 0.02 g g−1fresh weight day−1. There was a substantial increase in dry matter content of shoots and roots, especially during the first week of low temperature exposure, which for the greater part could be attributed to an accumulation of soluble sugars and starch. The freezing tolerance (LT50) of the leaf tissue gradually increased with 6 °C during the 6 weeks exposure, whereas freezing tolerance of roots was hardly affected. Upon low temperature exposure there was an increase in the content of water‐soluble non‐protein thiols (mainly glutathione), soluble sugars, starch, amino acids and total nitrogen in both shoots and roots. The most substantial increases in the content of thiols, sugars and amino acids already occurred within hours or a few days after the onset of the exposure. The nitrate content in shoots showed a rapid and strong decrease during low temperature exposure, however, in roots its content remained unaffected. It is proposed that the observed rapid increases in the content of various metabolites at low temperature are primarily due to an altered balance in their synthesis and their consumption in growth. There was no direct relation between increases in the content of the various metabolites and the degree of freezing tolerance of t

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00839.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractCuticles of several plant species are covered by tubular wax aggregates that are known to consist mainly of (S)‐nonacosan‐10‐ol. The present work addresses the question whether minor wax components may additionally contribute to these tubules. Thin layer chromatography was used to prepare secondary alkanediol fractions from leaf cuticular waxes ofNelumbo nuciferaandThalictrum flavum, containing nonacosane‐3,10‐diol, nonacosane‐4,10‐diol, nonacosane‐5,10‐diol, nonacosane‐7,10‐diol, nonacosane‐9,10‐diol and nonacosane‐10,13‐diol. From organic solutions all these compounds crystallized in tubular shapes. Possible crystal structures of relevant alkanediol isomers are proposed, in analogy to the lattice geometries of comparable aliphatic compounds. The resulting structural model shows that nonacosan‐10‐ol and various secondary alkanediols may join in metastable mixed crystals. According to the structural model proposed the admixture of alkanediols to nonacosan‐10‐ol aggregates should enhance

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00840.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe morphology of leaf venation has been studied repeatedly and various systems have been proposed for the classification of the observed leaf venation patterns. Almost nothing is known, however, about the functional properties of the various venation types. Using a computer modelling approach we analysed the water transport properties of typical craspedodromous and brochidodromous venation patterns. The water transport through the leaf and the veins was modelled as a fluid flow through a porous medium and the mathematical model was solved with the Finite Element Method. The simulations illustrate that the leaf margin represents a critical region in terms of water supply. The results provide a plausible functional explanation for three well known phenomena: 1) the correlation between craspedodromous venation and the formation of leaf teeth; 2) the fact that craspedodromous venation is more common in temperate than in tropical regions and 3) the fact that xeromorphic leaves tend to have more closed venation.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00841.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY