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  • Column liquid chromatography  (495)
  • photosynthesis  (212)
  • Zea mays  (193)
  • Fisheries
  • Inorganic Chemistry
  • Springer  (904)
  • 1990-1994  (904)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Examination of anAspergillus flavus resistant inbred of maize for crossresistance to sap beetle vectors (1994)
    Springer
    Entomologia experimentalis et applicata 71 (1994), S. 177-180 
    Details
    ISSN: 1570-7458
    Keywords: aflatoxin ; Carophilus ; Zea mays ; corn ; plant resistance ; Coleoptera ; Nitidulidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02382385
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  • 2
    Electronic Resource
    Electronic Resource
    Biological activity of maize leaf extracts against the African armyworm,Spodoptera exempta (1994)
    Springer
    Entomologia experimentalis et applicata 72 (1994), S. 17-23 
    Details
    ISSN: 1570-7458
    Keywords: plant varietal resistance ; armyworm ; Spodoptera exempta ; leaf extracts ; Zea mays ; feeding deterrent ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays L.) leaf tissue of cv Bastille and cv Michoacan 12 was extracted with n-hexane. The extracts were bioassayed against 5th instar African armyworm,Spodoptera exempta (Walker)(Lepidoptera: Noctuidae), by feeding the larvae on agar based media or sucrose impregnated glass fibre discs. The hexane extract of the ‘resistant’ cv Bastille exhibited feeding deterrency and toxicity which were not shown by the ‘susceptible’ cv Michoacan 12. The hexane extract of cv Bastille was adsorbed onto silica gel, the solution filtered off and the adsorbed component taken up into ethyl acetate. Bioassay of these fractions indicated that the toxic and deterrent action was retained in the ethyl acetate fraction. Preparative thin layer chromatography of the ethyl acetate fraction isolated two biologically active constituents. These were both growth inhibitors and lethal by ingestion to the 5th instar African armyworm. Implications for resistance in maize varieties to insect pests are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02382411
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of nickel on certain physiological and biochemical behaviors of an acid tolerantChlorella vulgaris (1994)
    Springer
    BioMetals 7 (1994), S. 193-200 
    Details
    ISSN: 1572-8773
    Keywords: Chorella vulgaris ; acid tolerance ; ATPase ; nickel toxicity ; nutrient uptake ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This study concerns the inhibitory effects of acid pH and nickel on growth, nutrient (NO3 - and NH4 +) uptake, carbon fixation, O2 evolution, electron transport chain and enzyme (nitrate reductase and ATPase) activities of acid tolerant and wild-type strains of Chlorella vulgaris. Though a general reduction in all these variables was noticed with decreasing pH, the tolerant strain was found to be metabolically more active than the wild-type. A reduced cation (NH4 +, Na+, K+ and Ca2+) uptake, coupled with a facilitated influx of anions (NH4 +, PO4 3- and HCO3 -), suggested the development of a positive membrane potential in acid tolerant Chlorella. Nevertheless, a tremendous increase in ATPase activity at decreasing pH revealed the involvement of superactive ATPase in exporting H+ ions and keeping the internal pH neutral. A difference in Na+ and K+ efflux of the two strains at decreasing pH suggests there is a difference in membrane permeability. The low toxicity of Ni in the acid tolerant strain may be due to the low Ni uptake brought about by a change in membrane potential as well as in permeability. Hence, the development of superactive ATPase and a change in both membrane potential and permeability not only offers protection against acidity, but also co-tolerance to metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00140491
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  • 4
    Electronic Resource
    Electronic Resource
    Manganese reduction in the rhizosphere of mycorrhizal and nonmycorrhizal maize (1994)
    Springer
    Mycorrhiza 5 (1994), S. 119-124 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus mosseae ; Manganese uptake ; Root exudation ; Manganese reduction ; Mycorrhizal effect ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of rhizosphere microorganisms and vesicular-arbuscular (VA) mycorrhiza on manganese (Mn) uptake in maize (Zea mays L. cv. Tau) plants was studied in pot experiments under controlled environmental conditions. The plants were grown for 7 weeks in sterilized calcareous soil in pots having separate compartments for growth of roots and of VA mycorrhizal fungal hyphae. The soil was left either uninoculated (control) or prior to planting was inoculated with rhizosphere microorganisms only (MO-VA) or with rhizosphere microorganisms together with a VA mycorrhizal fungus [Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe] (MO+VA). Mycorrhiza treatment did not affect shoot dry weight, but root dry weight was slightly inhibited in the MO+VA and MO-VA treatments compared with the uninoculated control. Concentrations of Mn in shoots decreased in the order MO-VA〉MO+VA〉control. In the rhizosphere soil, the total microbial population was higher in mycorrhizal (MO+VA) than nonmycorrhizal (MO-VA) treatments, but the proportion of Mn-reducing microbial populations was fivefold higher in the nonmycorrhizal treatment, suggesting substantial qualitative changes in rhizosphere microbial populations upon root infection with the mycorrhizal fungi. The most important microbial group taking part in the reduction of Mn was fluorescent Pseudomonas. Mycorrhizal treatment decreased not only the number of Mn reducers but also the release of Mn-solubilizing root exudates, which were collected by percolation from maize plants cultivated in plastic tubes filled with gravel quartz sand. Compared with mycorrhizal plants, the root exudates of nonmycorrhizal plants had two fold higher capacity for reduction of Mn. Therefore, changes in both rhizosphere microbial population and root exudation are probably responsible for the lower acquisition of Mn in mycorrhizal plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050048
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  • 5
    Electronic Resource
    Electronic Resource
    Efficacy of root litter as a biofertiliser (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 228-230 
    Details
    ISSN: 1432-0789
    Keywords: Fine root ; Root litter ; Biofertiliser ; Leucaena leucocephala ; Trigonella foenum-graecum ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The efficacy ofLeucaena leucocephala root litter as a natural biological fertiliser was assessed usingZea mays as a test plant. Up to 8% of the fine roots of the plants constituted root litter. This fine root litter was better than that ofTrigonella foenum-graecum at increasing the growth and productivity ofZea mays. The root litter increased the growth of maize shoots more than the growth of roots. This appears to be a general phenomenon when plant nutrients are insufficient, as in the present study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647671
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  • 6
    Electronic Resource
    Electronic Resource
    Impact of low-temperature stress on general phenylpropanoid and anthocyanin pathways: Enhancement of transcript abundance and anthocyanin pigmentation in maize seedlings (1994)
    Springer
    Planta 194 (1994), S. 541-549 
    Details
    ISSN: 1432-2048
    Keywords: Anthocyanin ; Cold stress ; mRNA ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in anthocyanin content and transcript abundance for genes whose products function in general phenylpropanoid metabolism and the anthocyanin pathway were monitored in maize (Zea mays L.) seedlings during short-term, low-temperature treatment. Anthocyanin and mRNA abundance in sheaths of maize seedlings increased with the severity and duration of cold. Anthocyanin accumulation was found in all tested lines that were genotypically capable of any anthocyanin production. Within 24 h of transferring 7-d maize (B37N) seedlings to 10° C, phenylalanine ammonia-lyase (Pal) (EC 4.3.1.5)-homologous and chalcone synthase (C2) (EC 2.3.1.74) transcript levels increased at least 8- and 50-fold, respectively, and 4-coumarate:CoA ligase (4Cl) (EC 6.2.1.12)-homologous and chalcone isomerase (Chi) (EC 5.5.1.6)-homologous transcripts increased at least 3-fold over levels in unstressed plants. Time-course studies showed thatPal (EC 4.3.1.5) andC2-transcript levels remained relatively constant for the first 12 h of cold stress, dramatically increased over the next 12 h, and declined to pretreatment levels within 2 d of returning coldstressed seedlings to ambient (25° C) temperature. Transcripts4Cl (EC 6.2.1.12) andChi (EC 5.5.1.6) increased in abundance within 6 h of cold stress, exhibited no further increase over the next 36 h, and declined to pretreatment levels upon returning seedlings to 25° C. Transcripts homologous to two regulatory (R, C1) and three structural (A1,A2, andBz2) anthocyanin genes increased at least 7- to 10-fold during cold treatment, exhibiting similar kinetics of accumulation as forPal (EC 4.3.1.5) andC2 transcripts. Transcripts encoded byBz1, the anthocyanin structural gene for UDP:glucose-flavonol glucosyltransferase (EC 2.4.1.91), were relatively abundant in control tissues and exhibited only a transient increase during the cold period. Our studies suggest that the genes of the anthocyanin biosynthetic pathway can be consideredcor (Cold-Regulation) genes, and because this pathway is well defined, it is an excellent subject for characterizing plant molecular responses to low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714468
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  • 7
    Electronic Resource
    Electronic Resource
    Ammonium-excreting Azospirillum sp. become intracellularly established in maize (Zea mays) para-nodules (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 1-8 
    Details
    ISSN: 1432-0789
    Keywords: Ammonium excretion ; Azospirillum brasilense ; Auxine ; 2,4-Dichlor-phenoxy-acetic acid ; Nitrogen fixation ; Paranodulation ; Maize ; Zea mays ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Maize seedlings develop nodule-like tumour knots (para-nodules) along primary roots when treated with the auxin 2,4-dichlor-phenoxy-acetic acid (2,4-D). Inoculated NH 4 + -excreting Azospirillum brasilense cells were shown to colonize these tumours, mostly intracellularly, promoting a high level of N2 fixation when microaerophilic conditions were imposed. The nitrogenase activity inside the para-nodules was less sensitive to free O2 than in non-para-nodulating roots. Both light and electron microscopy showed a dense bacterial population inside intact tumour cells, with the major part of the cell infection along a central tumour tissue. The bacteria colonized the cytoplasm with a close attachment to inner cell membranes. In an auxin-free growth medium, young 2,4-D-induced para-nodules grew further to become mature differentiated root organs in which introduced bacteria survived with a stable population. These results provide evidence that gramineous plants are potentially able to create a symbiosis with diazotrophic bacteria in which the NH 4 + -excreting symbiont will colonize para-nodule tissue intracellularly, thus becoming well protected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418663
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular cloning of two different cDNAs for maize acetyl CoA carboxylase (1994)
    Springer
    Plant molecular biology 24 (1994), S. 35-49 
    Details
    ISSN: 1573-5028
    Keywords: acetyl CoA carboxylase ; cDNA Cloning ; herbicide ; nucleotide sequence ; purification ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acetyl CoA carboxylase (EC 6.4.1.2) in plants is a chloroplast-localized, biotin-containing enzyme that catalyses the carboxylation of acetyl CoA to malonyl CoA, the first committed step of the fatty acid biosynthesis pathway. Acetyl CoA carboxylase is the target site for the monocotyledon-specific aryloxy-phenoxypropionate and cyclohexanedione groups of herbicides. We have purifed a herbicide-sensitive acetyl CoA carboxylase from maize leaves to homogeneity (specific activity 7 μmol min-1 mg-1), separating it during the purification from a minor herbicide-resistant acetyl CoA carboxylase. The purified enzyme is a dimer of 230 kDa subunits. Antibodies raised to the purified acetyl CoA carboxylase detected three cross-reacting clones in a maize leaf cDNA expression library, each having an insert of 4–4.5 kb. Restriction analysis and sequencing showed that the cDNAs were derived from two different transcripts. Comparison of the deduced amino acid sequences with those of chicken and yeast acetyl CoA carboxylases confirmed that both types encoded acetyl CoA carboxylase, corresponding to the C-terminal half of the enzyme. The overall identity of the maize and chicken sequences was 37% (58% similarity) but for some shorter regions was much higher. Analysis of six other acetyl CoA carboxylase clones recovered from the maize cDNA library showed four belonged to one type and two to the other. The nucleotide sequence similarity between the two types of cDNA was approximately 95% in the coding region but considerably less in the 3′-untranslated region. Northern blot analysis of maize RNA showed a single band of 8.2–8.5 kb for acetyl CoA carboxylase mRNA. Southern blot hybridisations indicated that there are probably no more than two genes in maize for acetyl CoA carboxylase. The possible significance of two different cDNAs for acetyl CoA carboxylase is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040572
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular analysis of wild-type and mutant alleles at the Opaque-2 regulatory locus of maize reveals different mutations and types of O2 products (1994)
    Springer
    Plant molecular biology 24 (1994), S. 949-959 
    Details
    ISSN: 1573-5028
    Keywords: Opaque-2 and opaque-2 genes ; allelic diversity ; Opaque-2 proteins ; transcriptional activator ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The expression of the various members of the zein multigene family in maize endosperm is controlled by different regulatory loci. One of these loci, Opaque-2, coding for a bZIP transcriptional factor, controls the expression of a subset of zein genes. Analysis of genomic DNA from plants carrying wild-type (O2) or mutant o2 alleles shows specific DNA restriction patterns that correlate with transcript types and their various gene products. Northern and western analyses show the presence in different wild types of a 1.7 kb transcript coding for different sizes of normal O2 proteins that migrate as doublets in the 68–72 kDa range. Among the various o2 mutants analysed we showed the occurrence of various null-transcript alleles, the presence of alleles with a normal size transcript which, however, produce a different-sized o2 protein, and a mutant producing both a normal size transcript and a longer transcript, but generating only a single o2 product migrating around 40 kDa. Analysis of other mutations (o7, fl2) known to affect zien polypeptide synthesis shows no interference of these mutations in the expression of the O2 gene products. The overall results indicate the occurrence of micro heterogeneity in the O2 wild-type genes and a broad spectrum of o2 mutations, both producing different sizes of O2 or o2 proteins. A nomenclature of the O2 and o2 genes based on the RFLP, transcripts and products of the various alleles is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014448
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  • 10
    Electronic Resource
    Electronic Resource
    Modification of carbonic anhydrase activity by antisense and over-expression constructs in transgenic tobacco (1994)
    Springer
    Plant molecular biology 25 (1994), S. 377-385 
    Details
    ISSN: 1573-5028
    Keywords: carbonic anhydrase ; antisense ; over-expression ; tobacco ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity and location of carbonic anhydrase has been modified by transformation of tobacco with antisense and over-expression constructs. Antisense expression resulted in the inhibition of up to 99% of carbonic anhydrase activity but had no significant impact on net CO2 assimilation. Stomatal conductance and susceptibility to water stress appeared to increase in response to the decline in carbonic anhydrase activity. An over-expression construct designed to increase cytosolic carbonic anhydrase abundance resulted in a significant increase in net activity, a small increase in stomatal conductance but little impact on CO2 assimilation. Chloroplastic carbonic anhydrase activity was enhanced by the expression of an additional construct which targeted the polypeptide to the organelle. The increase in chloroplastic carbonic anhydrase appeared to be accompanied by a concomitant increase in Rubisco activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043867
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  • 11
    Electronic Resource
    Electronic Resource
    Analysis of the cytosolic hsp70 gene family inZea mays (1994)
    Springer
    Plant molecular biology 25 (1994), S. 909-916 
    Details
    ISSN: 1573-5028
    Keywords: heat shock 70 kDa protein ; multigene family ; polymerase chain reaction ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study we have analysed the multigene family coding for the cytoplasmic heat shock 70 kDa proteins (hsp70) inZea mays. Fully degenerate primers were used in a polymerase chain reaction (PCR) to amplify selected regions of the hsp70 genes. Sequence and Southern blot analysis reveals that at least three highly conserved genes exist in maize. In addition, amplification reveals the presence of a conserved intron in all genes examined. Expression analysis shows that the hsp70 genes studied represent members of the inducible and constitutive families. The results obtained may indicate that there are subfamilies of cytoplasmic hsp70 genes expressed in higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028885
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  • 12
    Electronic Resource
    Electronic Resource
    Isolation of a cytochrome P450 homologue preferentially expressed in developing inflorescences ofZea mays (1994)
    Springer
    Plant molecular biology 25 (1994), S. 343-353 
    Details
    ISSN: 1573-5028
    Keywords: cytochrome P450 ; flower development ; meristem-specific gene ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four cDNA clones exhibiting preferential hybridization to transcripts present in developing maize tassels were isolated by differential screening. One of these cDNA clones hybridizes to transcripts detectable only in the shoot apex. The abundance of this transcript is significantly higher in developing inflorescence apices than in vegetative apices. DNA sequence analysis of a 2107 nucleotide cDNA clone corresponding to this transcript revealed that the transcript encodes a polypeptide of 547 amino acids, with a molecular mass of 58.4 kDa. This polypeptide shares significant sequence similarity with members of the cytochrome P450 monooxygenase gene superfamily, including the conserved C-terminal domains typical of the cytochrome P450 monooxygenases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043864
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  • 13
    Electronic Resource
    Electronic Resource
    Stability of the maize chromosomal high-mobility-group proteins, HMGa and HMGb,in vivo (1994)
    Springer
    Plant molecular biology 25 (1994), S. 565-568 
    Details
    ISSN: 1573-5028
    Keywords: chromatin ; high-mobility-group (HMG) proteins ; protein stability ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromosomal non-histone high-mobility-group (HMG) proteins represent essential components of eukaryotic chromatin and have also been isolated from a variety of plants. In maize, studies on structure and function of the two larger of the four major HMG proteins have recently been performed and are now extended by analysis of theirin vivo stability using pulse-chase experiments in a cell suspension culture. The half-life of the analyzed HMGa and HMGb proteins was found to be 65 h or more than 78 h, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043885
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  • 14
    Electronic Resource
    Electronic Resource
    Large tandem duplication associated with aMu2 insertion inZea mays B-Peru gene (1994)
    Springer
    Plant molecular biology 25 (1994), S. 817-828 
    Details
    ISSN: 1573-5028
    Keywords: B-Peru ; germinal revertants ; Mutator ; tandem duplication ; unequal recombination ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Theb locus ofZea mays encodes a transcriptional activator of the anthocyanin biosynthetic pathway. TheB-Peru allele is expressed in the aleurone layer of the seed, which results in dark purple pigmentation of this tissue. An unstableMutator-inducedB-Peru mutant allele,b-Perum220, displays weak, variable pigment and a high germinal reversion rate not characteristic of otherMutator insertions. Characterization of relevant regions ofb-Perum220 revealed aMu2 element insertion in one copy of a 534 bp sequence. This 534 bp sequence is tandemly triplicated in the progenitorB-Peru allele, upstream of theB-Peru transcription start site. In addition to theMu2 insertion, theb-Perum220 allele contains a newly formed large tandem duplication of 4.0 kb, which includes the promoter region and the first three exons of theB-Peru gene. TheMu2 element does not reside at any of the duplication breakpoints. The molecular study of eleven independent germinal revertants revealed five structural classes including structures in which the 4.0 kb tandem duplication is partially or completely deleted, theMu2 element is partially or completely deleted, or a combination of these events has occurred. We hypothesize that most of the revertants arose by unequal recombination between the duplicated regions. Based on these structural analyses, models are discussed to explain the reducedb gene expression inb-Perum220.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028876
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  • 15
    Electronic Resource
    Electronic Resource
    Identification of a maize root transcript expressed in the primary response to nitrate: characterization of a cDNA with homology to ferredoxin-NADP+ oxidoreductase (1994)
    Springer
    Plant molecular biology 26 (1994), S. 679-690 
    Details
    ISSN: 1573-5028
    Keywords: primary response ; ferredoxin NADP+ oxidoreductase ; nitrate ; cycloheximide ; Zea mays ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To more fully understand the biochemical and molecular events which occur in plants exposed to nitrate, cDNAs whose accumulation was enhanced in nitrate- and cycloheximide-treated maize (Zea mays L. W64A × W182E) roots were isolated. The 340 bp Zmrprn 1 (for Zea mays root primary response to nitrate) cDNA also hybridized with a probe enriched for nitrate-induced sequences, and was characterized further. Sequence analysis of a near full-length cDNA (Zmrprn 1A) showed strong homology (〉90% amino acid identity) with a root ferredoxin-NADP+ oxidoreductase (FNR) of rice, and 45–50% amino acid identity with leaf FNR genes. When expressed in Escherichia coli, the Zmrprn 1A cDNA produced a protein with NADPH: ferricyanide reductase activity, consistent with the enzymatic properties of an FNR. The Zmrprn 1 cDNA hybridized with a 1.4 kb transcript which was expressed in the maize root primary response to nitrate. That is, mRNA levels in roots increased rapidly and transiently in response to external nitrate, and low levels of nitrate (10 μM) induced transcript accumulation. The accumulation of the Zmrprn 1 transcript was not prevented by cycloheximide, indicating that the cellular factor(s) required for expression were constitutively present in maize roots. The Zmrprn 1 mRNA accumulated specifically in response to nitrate, since neither K+ nor NH4 + treatment of roots caused transcript accumulation. Maize leaves had about 5% of the transcript level found in roots, indicating a strong preference for expression of Zmrprn 1 in roots. Analysis of maize genomic DNA indicated the presence of only a single gene or very small gene family for the Zmrprn 1. Together, the data indicate that Zmrprn 1A encodes a nitrate regulated maize root FNR.
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    URL: http://dx.doi.org/10.1007/BF00013753
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  • 16
    Electronic Resource
    Electronic Resource
    Over-production of the D1 protein of photosystem II reaction centre in the cyanobacterium Synechococcus sp. PCC 7942 (1994)
    Springer
    Plant molecular biology 26 (1994), S. 709-721 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; photosynthesis ; protein turnover ; psbA ; tac promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI Q repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 μmol photons m-2 s-1 in the presence of 40 or 80 μg/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 μg/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI Q system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00013756
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  • 17
    Electronic Resource
    Electronic Resource
    Root- and shoot-specific responses of individual glutamine synthetase genes of maize to nitrate and ammonium (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1935-1946 
    Details
    ISSN: 1573-5028
    Keywords: glutamine synthetase genes ; regulation ; nitrate ; ammonium ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The responses of the five cytosolic-type glutamine synthetase (GS1) genes of maize to treatment of hydroponically grown seedlings with 10 mM KNO3 or 10 mM NH4Cl were analyzed. Non-coding 3′ gene-specific hybridization probes and radioanalytic imaging were used to quantitate individual gene transcript levels in excised roots and shoots before treatment and at selected times after treatment. Genes GS1−1 and GS1−2 exhibited distinct organ-specific responses to treatment with either nitrogen source. The GS1−1 transcript level increased over three-fold in roots, but changed little if any in shoots. In contrast, the GS1−2 transcript level increased over two-fold in shoots, but decreased in roots after treatment. Increased transcript levels were evident at 4 h after treatment with either nitrogen source, with maximum accumulations present at 8 h after treatment with ammonium and at 10–12 h after treatment with nitrate. The GS1−3 gene transcript level showed little or no change after treatment with either nitrogen source. The GS1−4 gene transcript level remained constant in shoots of treated seedlings, whereas in roots, it exhibited relatively minor, but complex responses to these two nitrogen sources. The GS1−5 gene transcript is present in very small amounts in seedlings, making it difficult to analyze its response to metabolites in young plants. These results provide support for the possibility that different cytosolic GS genes of maize play distinct roles in nitrogen metabolism during plant growth and differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019504
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  • 18
    Electronic Resource
    Electronic Resource
    Capturing of host DNA by a plant retroelement: Bs1 encodes plasma membrane H+-ATPase domains (1994)
    Springer
    Plant molecular biology 25 (1994), S. 137-140 
    Details
    ISSN: 1573-5028
    Keywords: DNA acquisition ; retrotransposon ; retrovirus ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recently identified maize retroelement Bs1 encodes domains of the plasma membrane H+-ATPase. This is the first example of host DNA captured by a plant retroelement and resembles the acquisition of oncogenes by vertebrate retroviruses. The ability to capture sequences from its host provides plant retroelements with a mechanism to alter gene structure which could be important for evolutionary adaptive change.
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    URL: http://dx.doi.org/10.1007/BF00023232
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    In vivo analysis of intron processing using splicing-dependent reporter gene assays (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1785-1795 
    Details
    ISSN: 1573-5028
    Keywords: intron ; maize ; splicing ; vectors ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanisms of intron recognition and processing have been well-studied in mammals and yeast, but in plants the biochemistry of splicing is not known and the rules for intron recognition are not clearly defined. To increase understanding of intron processing in plants, we have constructed new pairs of vectors, pSuccess and pFail, to assess the efficiency of splicing in maize cultured cells. In the pFail series we use translation of pre-mRNA to monitor the amount of unspliced RNA. We inserted an ATG codon in the Bz2 (Bronze-2) intron in frame with luciferase: this construct will express luciferase activity only when splicing fails. In the pSuccess series the spliced message is monitored by inserting an ATG upstream of the Bz2 intron in frame with luciferase: this construct will express luciferase activity only when splicing succeeds. We show here, using both the wild-type Bz2 intron and the same intron with splice site mutations, that the efficiency of splicing can be estimated by the ratio between the luciferase activities of the vector pairs. We also show that mutations in the unique U-rich motif inside the intron can modulate splicing. In addition, a GC-rich insertion in the first exon increases the efficiency of splicing, suggesting that exons also play an important role in intron recognition and/or processing.
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    URL: http://dx.doi.org/10.1007/BF00019492
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  • 20
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    Cloning and characterization of maize herbicide safener-induced cDNAs encoding subunits of glutathione S-transferase isoforms I, II and IV (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1855-1866 
    Details
    ISSN: 1573-5028
    Keywords: Glutathione S-transferase ; herbicide safener ; inducible gene expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several GSTs have been characterised in maize. GST I is a homodimer of 29 kDa subunits, GST II a hetrodimer of 27 kDa and 29 kDa subunits and GST IV a homodimer of 27 kDa subunits. We report the isolation and characterization of a herbicide-safener inducible cDNA clone, GST-27. Based on partial amino acid sequence, GST-27 encodes the 27 kDa subunit present in both glutathione S-transferase isoforms GST II and IV. Northern blotting was used to compare the expression patterns of GST-27 with that of GST-29. Transcripts corresponding to GST-27 were found to be constitutively expressed in RNA isolated from the root, but no expression was detected in RNA isolated from aerial parts of the plant. The application of herbicide safener caused a dramatic increase in the expression of GST-27 in all aerial plant parts tested. GST-29 was found to be constitutively expressed in RNA isolated from a number of maize tissues. The basal level of GST-29 expression showed a minimal increase upon herbicide safener treatment. Although a range of hormonal, environmental and physiological stimuli failed to elevate GST-27 levels, some increase in GST-27 mRNA was observed in the late stages of leaf senescence and after treatments resulting in phytotoxic effects.
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    URL: http://dx.doi.org/10.1007/BF00019498
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    Manganese reduction in the rhizosphere of mycorrhizal and nonmycorrhizal maize (1994)
    Springer
    Mycorrhiza 5 (1994), S. 119-124 
    Details
    ISSN: 1432-1890
    Keywords: Glomus mosseae ; Manganese uptake ; Root exudation ; Manganese reduction ; Mycorrhizal effect ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of rhizosphere microorganisms and vesicular-arbuscular (VA) mycorrhiza on manganese (Mn) uptake in maize (Zea mays L. cv. Tau) plants was studied in pot experiments under controlled environmental conditions. The plants were grown for 7 weeks in sterilized calcareous soil in pots having separate compartments for growth of roots and of VA mycorrhizal fungal hyphae. The soil was left either uninoculated (control) or prior to planting was inoculated with rhizosphere microorganisms only (MO-VA) or with rhizosphere microorganisms together with a VA mycorrhizal fungus [Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe] (MO+VA). Mycorrhiza treatment did not affect shoot dry weight, but root dry weight was slightly inhibited in the MO+VA and MO-VA treatments compared with the uninoculated control. Concentrations of Mn in shoots decreased in the order MO-VA 〉 MO+VA 〉 control. In the rhizosphere soil, the total microbial population was higher in mycorrhizal (MO+VA) than nonmycorrhizal (MO-VA) treatments, but the proportion of Mn-reducing microbial populations was fivefold higher in the nonmycorrhizal treatment, suggesting substantial qualitative changes in rhizosphere microbial populations upon root infection with the mycorrhizal fungi. The most important microbial group taking part in the reduction of Mn was fluorescent Pseudomonas. Mycorrhizal treatment decreased not only the number of Mn reducers but also the release of Mn-solubilizing root exudates, which were collected by percolation from maize plants cultivated in plastic tubes filled with gravel quartz sand. Compared with mycorrhizal plants, the root exudates of nonmycorrhizal plants had two fold higher capacity for reduction of Mn. Therefore, changes in both rhizosphere microbial population and root exudation are probably responsible for the lower acquisition of Mn in mycorrhizal plants.
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    URL: http://dx.doi.org/10.1007/BF00202343
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    Phylogenetic analysis of Sorghum and related taxa using internal transcribed spacers of nuclear ribosomal DNA (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 26-32 
    Details
    ISSN: 1432-2242
    Keywords: Sorghum ; Zea mays ; Phylogeny rDNA sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phylogenetic relationships of the genus Sorghum and related genera were studied by sequencing the nuclear ribosomal DNA (rDNA) internal transcribed spacer region (ITS). DNA was extracted from 15 Sorghum accessions, including one accession from each of the sections Chaetosorghum and Heterosorghum, four accessions from Parasorghum, two accessions from Stiposorghum, and seven representatives from three species of the section Sorghum (one accession from each of S. propinquum and S. halepense, and five races of S. bicolor). The maize (Zea mays) line, H95, and an accession from Cleistachne sorghoides were also included in the study. Variable nucleotides were used to construct a strict consensus phylogenetic tree. The analyses indicate that S. propinquum, S. halepense and S. bicolor subsp. arundinaceum race aethiopicum may be the closest wild relatives of cultivated sorghum; Sorghum nitidum may be the closest 2n=10 relative to S. bicolor, the sections Chaetosorghum and Heterosorghum appear closely related to each other and more closely related to the section Sorghum than Parasorghum; and the section Parasorghum is not monophyletic. The results also indicate that the genus Sorghum is a very ancient and diverse group.
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    URL: http://dx.doi.org/10.1007/BF00226978
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  • 23
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    Estimation of sampling variance of molecular marker data using the bootstrap procedure (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 259-264 
    Details
    ISSN: 1432-2242
    Keywords: RFLP ; Bootstrap ; Sampling variance ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Knowledge of genetic relationships among genotypes is useful in a plant breeding program because it permits the organization of germplasm and provides for more efficient sampling. The genetic distance (GD) among genotypes can be estimated using random restriction fragment length polymorphisms (RFLPs) as molecular markers. Knowledge of the sampling variance associated with RFLP markers is needed to determine how many markers are required for a given level of precision in the estimate of GD. The sampling variance for GD among all pairs of 37 maize (Z. mays L.) inbred lines was estimated from 1202 RFLPs. The 1202 polymorphisms were generated from 251 enzyme-probe combinations (EPC). The sampling variance was used to determine how large a sample of RFLPs was required to provide a given level of precision. The coefficient of variation (CV) associated with GD has a nearly linear relationship between its expected standard deviation and mean. The magnitude of the decrease in the mean CV for GD with increasing numbers of bands was dependent upon the sampling unit; e.g., individual polymorphic bands vs EPC, and the degree of relatedness among the inbreds compared. The rate of reduction in mean CV with increasing sample size was the same regardless of the restriction enzyme used, BamHI, EcoRI or HindIII, when the bootstrap sampling units were individual polymorphic bands. In constrast, although the rate of reduction (slopes) was the same, the intercepts of the mean CVs were different when EPCs were used as the bootstrap sampling unit. This difference was due to the higher number of bands per EPC in BamHI (4.94) compared with EcoRI (4.83) and HindIII (4.63).
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    URL: http://dx.doi.org/10.1007/BF00225151
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    Haplo-diploid gene expression and pollen selection for tolerance to acetochlor in maize (1994)
    Springer
    Theoretical and applied genetics 88 (1994), S. 780-784 
    Details
    ISSN: 1432-2242
    Keywords: Acetochlor tolerance ; Gene expression Pollen selection ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objectives of this research were to determine if genes controlling the reaction to the herbicide acetochlor in maize (Zea mays L.) are active during both the haploid and the diploid phases of the life cycle and if pollen selection can be utilized for improving sporophytic resistance. Pollen of eight inbred lines, previously characterized through sporophytic analysis for the level of tolerance to acetochlor, showed a differential reaction to the herbicide forin vitro tube length; moreover, such pollen reactions proved to be significantly correlated (r =0.786*,df=6) with those of the sporophytes producing the pollen. Pollen analysis of two inbred lines (i.e. Mo17, tolerant, and B79, susceptible) and their single cross showed that thein vitro pollen-tube length reaction of the hybrid was intermediate between those of two parents. An experiment on pollen selection was then performed by growing tassels of Mo17xB79 in the presence of the herbicide. Pollen obtained from treated tassels showed a greater tolerance to acetochlor, assessed asin vitro tube length reaction, than pollen obtained from control tassels. Moreover, the backcross [B79 (Mo17xB79)] sporophytic population obtained using pollen from the treated tassels was more tolerant (as indicated by the fresh weight of plants grown in the presence of the herbicide) than was the control backcross population. The two populations did not differ when grown without the herbicide. These findings indicate that genes controlling the reaction to acetochlor in maize have haplodiploid expression; consequently, pollen selection can be applied for improving plant tolerance.
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    URL: http://dx.doi.org/10.1007/BF01253986
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    Genetic and amino-acid analysis of two maize threonine-overproducing, lysine-insensitive aspartate kinase mutants (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 767-774 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Aspartate kinase Threonine-overproducing mutants ; Lysine ; Methionine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aspartate-derived amino-acid pathway leads to the production of the essential amino-acids lysine, methionine, threonine and isoleucine. Aspartate kinase (AK) is the first enzyme in this pathway and exists in isoforms that are feedback inhibited by lysine and threonine. Two maize (Zea mays L.) threonine-overproducing, lysine-insensitive AK mutants (Ask1-LT19 and Ask2-LT20) were previously isolated. The present study was conducted to determine the map location of Ask2 and to examine the amino-acid profiles of the Ask mutants. The threonine-overproducing trait conferred by Ask2-LT20 was mapped to the long arm of chromosome 2. Both mutants exhibited increased free threonine concentrations (nmol/mg dry weight) over wild-type. The percent free threonine increased from approximately 2% in wild-type kernels to 37–54% of the total free amino-acid pool in homozygous mutant kernels. Free methionine concentrations also increased significantly in homozygous mutants. Free lysine concentrations were increased but to a much lesser extent than threonine or methionine. In contrast to previous studies, free aspartate concentrations were observed to decrease, indicating a possible limiting factor in threonine synthesis. Total (free plus protein-bound) amino-acid analyses demonstrated a consistent, significant increase in threonine, methionine and lysine concentrations in the homozygous mutants. Significant increases in protein-bound (total minus free) threonine, methionine and lysine were observed in the Ask mutants, indicating adequate protein sinks to incorporate the increased free amino-acid concentrations. Total amino-acid contents (nmol/kernel) were approximately the same for mutant and wild-type kernels. In five inbred lines both Ask mutations conferred the threonine-overproducing phenotype, indicating high expressivity in different genetic backgrounds. These analyses are discussed in the context of the regulation of the aspartate-derived amino-acid pathway.
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    URL: http://dx.doi.org/10.1007/BF00223717
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    Identification of opaque-2 genotypes in segregating populations of Quality Protein Maize by analysis of restriction fragment length polymorphisms (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 407-412 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Opaque-2 ; RFLPs Marker-assisted selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quality Protein Maize (QPM) is a name given to genetically modified opaque-2 maize with hard endosperm. The opaque-2 mutation conditions a reduction in the amount of zein seed storage protein; zeins are deficient in the essential amino acids lysine and tryptophan, and mutant seed have a higher nutritional value. To utilize the potential of opaque-2 maize, elite inbreds can be converted to o2/o2 forms and subsequently to hard endosperm opaque-2. Since opaque-2 is recessive and endosperm specific, conventional backcross procedures to convert elite inbreds to opaque-2 forms are inefficient. To alleviate this problem, a marker-assisted selection procedure was developed for the Texas A&M University Quality Protein Maize breeding program. Hybridization of an O2 cDNA probe to blots of DNA from plants carrying O2 and o2 alleles showed that restriction fragment length polymorphisms (RFLPs) exist between the W64A o2 allele and O2 alleles of Mo17 and TX5855 inbred lines. To identify the opaque2 genotypes in segregating populations, an RFLP marker assay combining the O2 cDNA probe and HindIII-digestion of genomic DNA was developed. The effectiveness of the O2 RFLP marker assay was tested under field conditions using F2 and backcross populations of several hard endosperm opaque-2 lines. A comparison of the genotypes identified by RFLP analysis with the seed phenotypes of the next generation indicated that this procedure is accurate and can be used for identifying O2/O2, O2/o2, and o2/o2 genotypes of individual juvenile plants in breeding populations.
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    URL: http://dx.doi.org/10.1007/BF00225374
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    Quantitative transient gene expression: Comparison of the promoters for maize polyubiquitin1, rice actin1, maize-derivedEmu andCaMV 35S in cells of barley, maize and tobacco (1994)
    Springer
    Transgenic research 3 (1994), S. 249-255 
    Details
    ISSN: 1573-9368
    Keywords: transient gene expression ; β-glucuronidase ; luciferase ; Hordeum vulgare ; Zea mays ; Nicotiana tabacum ; quantitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The particle gun approach was used for the quantification of promoter efficiency in a test system for transient gene expression. β-Glucuronidase was used as reporter gene for determining promotote strength. The variability inherent in this gene transfer system was considerably reduced by calculating a transformation efficiency factor given by the expression of a cotransferred second reporter gene (firefly luciferase). The calibration of β-glucuronidase activity by the transformation efficiency factor caused a lower statistical variance of the values and allowed reliable results to be obtained with a smaller set of repetitions. The CaMV 35S promoter (as a control) and the monocot-specific promoters for maize polyubiquitin1, rice actin 1 and the maize-derivedEmu were characterized and compared with respect to expression strength, as tested under identical conditions in suspension cell cultures of maize, barley and tobacco. Compared to the 35S promoter, the monocot-specific promoters show up to 15-fold higher expression in maize and barley but give only weak expression in tobacco. No expression was found for the rice actin 1 promoter in tobacco. The level of reporter gene expression is influenced by the osmotic potential in the agar medium. For theEmu promoter, the calibrated β-glucuronidase activities remained mearly constant at low sucrose concentrations. Above 8% sucrose, the calibrated activities increased steadily with increasing osmotic conditions, reaching a three-to four-fold higher level at the highest sucrose concentration (32%) as compared to the standard concentration (4% sucrose) in the medium.
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    URL: http://dx.doi.org/10.1007/BF02336778
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    Allosteric regulation of the Golgi inosine diphosphatase from corn roots (1994)
    Springer
    Protoplasma 179 (1994), S. 131-141 
    Details
    ISSN: 1615-6102
    Keywords: Inosine diphosphatase ; Golgi membranes ; Zea mays ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Light microsomes of corn roots, enriched in endoplasmic reticulum and Golgi membranes, have an IDPase activity which is stimulated by Triton X-100 and by cold storage. In the native state, the enzyme activity does not follow Michaelis-Menten kinetics. It hydrolyses IDP with K0.5 of about 900 μM and Vmax of 300–400 nmol Pi/mg protein/min. In the presence of Triton X-100, the enzyme is maximally stimulated and it renders to a Michaelis-Menten behavior with a Km of about 500 μM and a Vmax of 800–1200 nmol Pi/mg protein/min. The maximal effect of the detergent occurs at about 1 mM IDP (270%), being reduced (190%) at high IDP concentrations (〉2 mM) which, per se, have a slight stimulatory effect on the enzyme. On the other hand, we observed that ATP (〉2 mM) and adenosine inhibit the IDPase. The effects of the nucleotides and of the adenosine are abolished in the presence of Triton X-100, which makes the enzyme fully active. Furthermore, we observed that detergent treatment of the membranes reduces the change in the activation energy which occurs at 10 °C and eliminates cooperative effects, as revealed by the Arrhenius analysis and the Hill analysis, respectively. We also observed that IDPase inhibition by ATP is maximal at low IDP concentrations (1 mM), whereas it decreases at high concentrations of IDP (4 mM), which promote maximal velocities in the native enzyme. Conversely, the inhibitory effect of adenosine is not reduced at high IDP concentrations. Pyrophosphate also inhibits the IDPase, but the effect is non-competitive and it is cumulative with that of ATP. We also observed that the latent activity of the IDPase (Triton-stimulated IDPase) is reduced by pre-treatment of the membranes with glutaraldehyde. The results indicate that Golgi IDPase is an allosteric enzyme which is positively modulated by IDP and negatively modulated by ATP and adenosine. Pyrophosphate inhibits the IDPase, but it seems to act at the catalytic site, whereas the other modulators appear to interact with a distinct regulatory site.
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    URL: http://dx.doi.org/10.1007/BF01403951
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    Mechanosensory microtubule reorientation in the epidermis of maize coleoptiles subjected to bending stress (1994)
    Springer
    Protoplasma 182 (1994), S. 96-101 
    Details
    ISSN: 1615-6102
    Keywords: Auxin ; Mechanical stress ; Mechanosensor ; Microtubule orientation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plants respond to mechanical stress by adaptive changes in growth. Although this phenomenon is well established, the mechanism of the perception of mechanical forces by plant cells is not yet known. We provide evidence that the cortical microtubules sub-adjacent to the growth-controlling outer epidermal cell wall of maize coleoptiles respond to mechanical extension and compression by rapidly reorientating perpendicular to the direction of the effective force change. These findings shed new light on many seemingly unrelated observations on microtubule reorientation by growth factors such as light or phytohormones. Moreover, our results suggest that microtubules associated with the plasma membrane are causally involved in sensing vectorial forces and provide vectorial information to the cell that can be utilized in the orientation of plant organ expansion.
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    Improved recovery of (1→3),(1→4)-β-D-glucan synthase activity from Golgi apparatus ofZea mays (L.) using differential flotation centrifugation (1994)
    Springer
    Protoplasma 180 (1994), S. 92-97 
    Details
    ISSN: 1615-6102
    Keywords: Zea mays ; (1→3), (1→4)-β-D-glucan ; Glucan synthase ; Golgi apparatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The synthesis of (1→3), (1→4)-β-D-glucan (MG) is associated with the Golgi apparatus of maize. Identification of in vitro reaction products by enzymic hydrolysis and separation of diagnostic oligosaccharides by HPLC was used as a specific assay for MG synthase activity. Large quantities of highly enriched membrane are needed to study the enzyme components of MG synthesis. We directly obtained highly enriched Golgi apparatus in a single flotation centrifugation, without the necessity of an initial downward centrifugation. This new procedure has improved the yield of Golgi apparatus, and has improved recovery of MG synthase activity. The substrate in glucan synthase reactions is UDP-Glc, but UDP-Glc is also a substrate in many other reactions, including the production of simple glucosides. In addition, much of the labeled Glc from UDP-Glc is broken down to Glc-1-P and Glc under MG synthase reaction conditions. We have explored some inhibitors of phosphatase, phosphorylase, phosphodiesterase, and glucosidase activities in order to minimize these competing reactions and increase the activity of MG synthase.
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    URL: http://dx.doi.org/10.1007/BF01379227
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    Determination of triamterene in urine by HPLC using fluorescence detection and column-switching (1994)
    Springer
    Chromatographia 38 (1994), S. 29-34 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching ; Determination of triamterene ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic method incorporating column-switching and fluorimetric detection for the determination of triamterene in untreated urine, is described. The urine samples (5 μL) were directly introduced onto an Hypersil ODS-C18, 30 μm (20 mm×2.1 mm I.D.) pre-column. Polar urinary compounds were removed by flushing the pre-column with water for 1 min, and the analyte was then switched onto an HP-LiChrospher RP C18,5 μm (125 mm×4mm ID) analytical column using an acetonitrile/phosphate buffer gradient elution. Fluorescence detection was performed at 230 nm excitation and 430 nm emission wavelengths. The recovery of drug was 102±2% in the 0.10–20.0 μg/mL concentration range, the limit of detection being 5 ng/mL. A validation of the usefulness of this procedure was accomplished by analysing urine extracts obtained from real samples.
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    URL: http://dx.doi.org/10.1007/BF02275723
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    Statistical evaluation of the validity of a method for characterizing stationary phases for reversed-phase liquid chromatography based on retention of homologous series (1994)
    Springer
    Chromatographia 38 (1994), S. 137-146 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Characterization of reversed phases ; Column hydrophobicity ; Column hydrophylicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The validity of a method for characterizing stationary phases for reversed-phase, liquid chromatography, based on the use of homologous series, has been evaluated. The method is based on a retention model which describes the dependence of the logarithm of the capacity factor on mobile phase composition and the carbon number of specific homologous series. A first-order as well as a second-order version of this model was investigated. The second-order model proved to be a significant improvement on the first-order model, even for smaller mobile-phase ranges. Nevertheless both models showed a significant lack of fit, reflecting the incompleteness of these models. Therefore, it is very questionable whether this method is suitable to describe HPLC-column characteristics like hydrophobicity and hydrophylicity.
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    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 3. Sudden-transition gradient elution of styrene/ acrylonitrile copolymers (1994)
    Springer
    Chromatographia 38 (1994), S. 749-755 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/acrylonitrile) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and acrylonitrile could be separated according to composition by gradient elution through methanol after injection inton-heptane and sudden addition of 50, 60, or 70 vol% tetrahydrofuran. The peak sequence was the same as with a common binary gradientn-heptane/tetrahydrofuran, i.e., retention increased with acrylonitrile content of the samples. With copolymers containing 37, 31, or 26% acrylonitrile, the elution characteristics in the ternary systems could be logically extrapolated towards the points measured in the corresponding binary gradient system.
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    Chiral recognition of structurally related aminoalkylphosphonic acid derivatives on an acetylated beta-cyclodextrin bonded phase (1994)
    Springer
    Chromatographia 38 (1994), S. 771-775 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral recognition ; Aminoalkylphosphonic acid derivatives ; β-cyclodextrin bonded phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An acetylated β-cyclodextrin column was used to analyse the enantiomeric resolution of a number of aminophosphonic acids. Effects of the structure of these compounds on the extent of separation was examined. Molecular modelling studies were also carried out in an attempt to relate any interaction between the amino and phosphonic acid groups to chiral recognition by the stationary phase.
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    Interaction of cyclodextrins with drugs. Chromatographic investigation using a cyclodextrin bonded-phase and its application to chiral separations (1994)
    Springer
    Chromatographia 38 (1994), S. 381-385 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Association constants ; Frontal analysis ; Cyclodextrin bonded-phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The interaction between cyclodextrin and the drug (1R,2S,3S,4S)-(5Z)-7-(3-((phenylsulfonyl)amino)bicyclo[2.2.1]hept-2-yl)hept-5-enoic acid ((+)-S-145), was studied using α-, β-, and γ-cyclodextrin bonded-phase columns. Retention behavior of (+)-S-145 on these columns revealed that the strength of inclusion was β→γ→α-cyclodextrin. Interaction between β-cyclodextrin and (+)-S-145 was found to increase as the proportion of carboxylic ion in the (+)-S-145 molecule increased. Comparison of binding capacities of these bondedsilica gels obtained by frontal analysis and surface coverage indicated that availability of the immobilized β- and γ-cyclodextrin was 20–25%. The synthesized β-cyclodextrin bonded-phase column was superior to that of commercial columns in terms of chiral separation of (±)-S-145. A typical usage of the β-cyclodextrin column is discussed for separation of (±)-S-145 in plasma samples.
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    URL: http://dx.doi.org/10.1007/BF02269784
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    Reverse phase high-performance liquid chromatographic determination of primary and secondary aliphatic alcohols as phthalate monoesters by UV detection (1994)
    Springer
    Chromatographia 38 (1994), S. 417-420 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Primary and secondary aliphatic alcohols ; Aqueous derivatization ; Phthalic acid monoesters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Determination of primary and secondary aliphatic alcohols in aqueous and nonaqueous solutions by high-performance liquid chromatography (HPLC) is described. The alcohol is derivatized with phthalic anhydride to yield the corresponding monophthalate. Separation of the derivative is achieved on an ODS-10 reverse phase (RP) column by elution with an appropriate isocratic mobile phase of acetonitrile and aqueous phosphoric acid (0.1%). Detection is accomplished by UV absorption at 230 nm or 280 nm giving linear calibration plots, for alcohols in aqueous solution from 0.05% to 0.50% (w/v) and in pyridine solution from 0.0025% to 0.0250% (w/v).
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    URL: http://dx.doi.org/10.1007/BF02269829
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    Solute-micelle association constants of some polynuclear aromatic hydrocarbons by micellar liquid chromatography with alcohol additives to mobile phase (1994)
    Springer
    Chromatographia 38 (1994), S. 342-348 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hybrid mobile phases containing alcohols ; Solute-micelle association constants ; Polynuclear aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The interaction between some polynuclear aromatic hydrocarbons of environmental concern, and sodium dodecylsulphate and hexadecyltrimethylammonium bromide in the presence of methanol, 2-propanol and n-butanol has been evaluated by high-performance liquid chromatography using micellar mobile phases. Solute-micelle association constants have been determined for the compounds investigated. The results show that the addition of the alcohol to the mobile phase decreases the association constant values, methanol 〈2-propanol 〈n-butanol, relative to those in the absence of any additive.
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    URL: http://dx.doi.org/10.1007/BF02269778
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    Solid phase extraction applied to the determination of biogenic amines in wines by HPLC (1994)
    Springer
    Chromatographia 38 (1994), S. 571-578 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wine ; Biogenic amines ; Solid-phase extraction ; Derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method suitable for the determination of 19 biogenic amines in wine has been developed. The method involves derivatization of amines by treatment with dansyl chloride and solid-phase extraction of the derivatives. Prior to the derivatization procedure, clean-up of the wine sample with polyvinylpyrrolidone is carried out. Reversed-phase gradient elution HPLC with UV detection at 250 nm was used to determine these compounds. Some consideration was given to the effect of temperature on the separation process. Linearity of derivatization was obtained for amounts of all the biogenic amines ranging from 500 μg·L−1 to 20 mg·L−1. Limits of detection (signal-to-noise ratio=3) of the amines were similar for all the dansylderivatives (between 50 and 150 μg·L−1). Addition of standard amines was used for the determination of amine recoveries. These were better than 85% for ethanolamine, tryptamine, phenetylamine, putrescine, cadaverine and histamine. The overall process was succesfully applied to identify and quantify biogenic amines in white and red wines.
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    URL: http://dx.doi.org/10.1007/BF02277156
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    Enantiomer separaton of tifluadom and analogues by liquid chromatography with cellulose-based chiral stationary phases (1994)
    Springer
    Chromatographia 38 (1994), S. 629-632 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral/enantiomeric iseparation ; Cellulose-based chiral phases ; Tifluadom analogues ; 2-acylaminomethyl-1,4-benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolution of nine recamic mixtures of tifluadom analogues has been evaluated using the chiral stationary phases Chiralcel OD and Chiralcel OJ. The separation was performed on an analytical scale to optimize the conditions for chiral resolution, approaching baseline separation, of the two enantiomers. Eight racemates were baseline separated on Chiralcel OJ using a mobile phase of hexane/2-propanol.
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    URL: http://dx.doi.org/10.1007/BF02277166
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    Comparative study of solid-phase extraction of phenolic compounds. Influence of the ion pair reagent (1994)
    Springer
    Chromatographia 38 (1994), S. 579-584 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Ion-pair solid-phase extraction ; Comparison of sorbents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparative study of the solid phase extraction of phenolic compounds in water was carried out. Three different sorbents, C18, CH and PLRP-S, were tested for the preconcentration process in order to determine phenolic compounds in water at μg l−1 levels by reversed-phase LC separation and diode-array detection. The addition of an ion-pair reagent in the extraction process was also studied in order to increase the breakthrough volume of some compounds. Using the optimized conditions the limit of detection was less than 0.5 μg l−1, the maximum admissible concentration (MAC) in drinking water. The method was applied to determine phenolic compounds in Ebro river water however no phenols were found within the detection limits of the method.
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    URL: http://dx.doi.org/10.1007/BF02277157
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    Extraction of basic drugs from whole blood and determination by high performance liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 617-623 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Extraction-determination ; Basic drugs ; Blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the extraction of basic drugs from whole blood based on the use of a buffered protein precipitating reagent at pH9, to form NiWO4 in biological fluids and a ternary organic extracting phase of density below 1 is proposed. The extract is analysed by high performance liquid chromatography using a Hypersil C8 column and detection at 230 nm; the mobile phases used consist of binary mixtures of acetonitrile and aqueous solutions containing 20 mmol/l ofn-propylamine at pH 5 andn-hexylamine at pH 4, as blockers of the free silanol groups. The proposed method was applied to the determination of 16 basic drugs including narcotics, analgesics, cocaine-related compounds and adulterants, as well as 8 benzodiazepines, in whole blood.
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    URL: http://dx.doi.org/10.1007/BF02277164
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    Determination of imazethapyr and imazapyr residues in soil by coupled-column liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 62-66 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Imidazolinone herbicides in soil ; Imazethapyr ; Imazapyr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A column-switching method using two separation columns combined with UV detection at 260 or 236 nm has been used to determine the imidazolinone herbicides imazethapyr and imazapyr in soils. The residues were extracted from the soil with 0.1 M aqueous sodium carbonate solution and, after adjusting the pH to 2.0, the solution was partitioned with dichloromethane. Limits of determination for imazethapyr and imazapyr were 3 μg/kg. Recoveries were from 55 to 75% for both imidazolinone herbicides in the range 3–100 μg/kg in soil.
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    URL: http://dx.doi.org/10.1007/BF02320459
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    A novel derivatisation procedure for inorganic mercury(II) for HPLC analysis (1994)
    Springer
    Chromatographia 39 (1994), S. 246-248 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mercury ; Diphenylethynylmercury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new procedure for derivatisation of inorganic mercury(II) to diphenylethynylmercury with simultaneous extraction into dichloromethane is proposed. The organomercury derivative is effectively analysed by HPLC using UV detection. The calibration curve is linear over three orders of magnitude (0.02–50 mg L−1 Hg); the detection limit is 0.1 ng Hg. A preliminary study of the effect of potential interfering agents, in particular Cu(II), Zn(II), Cd(II), Pb(II), and cysteine, and applications of the present methodology to real environmental samples are presented.
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    URL: http://dx.doi.org/10.1007/BF02274507
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    Determination of short chain aliphatic acids in silage effluents by ion exclusion chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 43-51 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exclusion ; Alipathic acids ; Silage effluents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Short chain aliphatic acids are important components of the dissolved organic matter in silage effluents. Although ion exclusion chromatography offers some advantages for the analysis of these compounds, no attempt has yet been made to prove the suitability of this method for silage effluent analysis. In order to gain experience in this field, the separation characteristics of a Dionex ion exclusion column (IonPac-ICE As5) have been evaluated, the separation conditions have been improved, and several sample clean-up methods have been checked. Ten effluents generated during silaging of five different crops were collected from Bavarian farms and analyzed. Lactic and acetic acids were the predominant aliphatic acids. Pyruvic, formic, propionic, and succinic acid were detected in all samples, whereas glyceric and iso-citric acid were found in a few samples only. If some restrictions of substance specificity and separation efficiency can be accepted, the analytical method presented will be a reliable tool for the analysis of carboxylic acids in silage effluents.
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    URL: http://dx.doi.org/10.1007/BF02275725
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    Polymer encapsulated packing material for reversed phase liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 756-760 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polymer encapsulated packings ; Poly(ethylstyrene-divinylbenzene) ; Preparation and evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A series of polymer-encapsulated packing materials for reversed phase high-performance liquid chromatography was prepared by radical polymerization of ethylstyrene and divinylbenzene with vinyl-modified silica in solution. Some characteristics such as polymer structure, swelling propensity, residual silanols, column efficiency and retention properties were evaluated. Such material is easy to pack and yields high column efficiencies. Its superior performance for the separation of mixtures of aromatic hydrocarbons, amino- and hydroxyl group containing compounds are demonstrated by several examples.
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    URL: http://dx.doi.org/10.1007/BF02269632
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    Application of β-cyclodextrin for the analysis of estrogenic steroids in human urine by high-performance liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 168-172 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; β-Cyclodextrin in mobile phase ; Estrogens ; Pregnant and non-pregnant women
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure is described for simultaneous determination of estriol, estrone and 17β-estradiol in human urine. After acid hydrolysis of the sulphate conjugates, the estrogens were extracted into diethyl ether. The ether extracts were concentrated and applied directly to an HPLC column. Using a 25 cm C-18 column and acetonitrile-water modified by the addition of β-cyclodextrin as mobile phase, the separation of estriol, estradiol and estrone was achieved within 20 minutes. The extraction of estrogens from the biological matrix is excellent. Estrogens were detected using a UV-detector (280 nm) or a spectrofluorimetric detector (λexc=280nm, λem=312 nm). The latter detection system has been used for the determination of estrogens in the urine of non-pregnant women. The procedure is simple and can be used in clinical practice.
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    URL: http://dx.doi.org/10.1007/BF02290331
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    Convergence of retention for small solutes in reversed-phase liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 158-162 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase chromatography ; Retention mechanism ; Retention convergence ; Small molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown theoretically that when the concentration of organic solvent in the mobile phase increases, or solute size decreases, log k′ values of small solutes in reversed-phase liquid chromatography (RPLC) will tend to have a minimum value called the convergence point. A theoretical model for evaluating the convergent coordinates of small solutes is presented by using a stoichiometric displacement model for retention (SMDR). The physical meaning of the coordinates of each kind of convergence are also elucidated. The convergence points have either two-dimensional coordinates with a common ordinate (the logarithm of the phase ratio of the column, log φ) or threedimensional corrdinates with two common axes: — log φ and the logarithm of the molar concentration of the pure displacing agent in mobile phase, log aD. The other axis relates to the nature of the solutes, such as carbon number of a homolog, van der Waal's surface area, hydrophobic fragment constant etc. for the latter and those and/or concentration axis for the former. The model was tested with published data and found to give a good fit.
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    CP/MAS NMR investigations of silica gel surfaces modified with aminopropylsilane (1994)
    Springer
    Chromatographia 38 (1994), S. 283-290 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phase (CBP) ; Silica-gel with aminopropylsilyl ligands ; Physico-chemical characterization ; CP/MAS NMR investigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Aminopropyl chemically bonded phases for high performance liquid chromatography (HPLC) have been prepared using mono- and trifunctional methoxyor ethoxysilanes. Three types of silica gel with different surface characteristics were used as support for the chemically bonded phases (CBPs). Surface characteristics of the packings before and after chemical modification were determined by porosity parameters, elemental analysis and CP/MAS NMR spectroscopy.29Si and13C CP/MAS NMR investigations gave informations about different interactions between aminosilyl ligands and/or these ligands and/or water molecules condensed in the pores of the silica gel surface. With decreasing pore diameter of the silica gel the proportion of protonated aminopropyl ligand increases.
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    The application of ‘Z’-shaped UV cells in open-tubular capillary column liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 313-316 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Open-tubular capillary columns ; ‘Z’-shaped UV cells ; Solvent make-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary ‘Z’-shaped UV cells for packed capillary columns cannot be used in open-tubular capillary column liquid chromatography (OT-LC) because of their relatively large volume. With post-column solvent make-up, a commercial ‘Z’-shaped cell (volume 100 nl) was used in our OT-LC system, resulting in 9-fold sensitivity increase against on-column UV detection and with little efficiency loss. A small volume (5 nl) ‘Z’-shaped cell allows the direct coupling of the cell to high efficiency columns. For dilute samples, 9-19-fold sensitivity enhancement could be obtained. However, column efficiency decreases with increasing signal level as a result of peak deformation.
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    Interconversion of cyclosporin molecular form inducing peak broadening, tailing and splitting during reversed-phase liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 359-364 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cyclosporin ; Reversible conversion ; Activation energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase liquid chromatography of cyclosporin A, a peptide immunosuppressant, at various temperatures produced remarkably different chromatograms. At 60°C one sharp peak was obtained, at 23°C this became a single broad peak and between 15° and 0°C this became one high sharp peak followed by a tailing or low plateau. Remarkably different chromatograms were produced also by varying the mobile phase flow-rate. The effects of both temperature and flow-rate on the chromatogram could be accounted for by interconversion between two forms of the cyclosporin molecule. Kinetic analysis showed that one form was converted by first-order kinetics with a half-life of 2.0 min at 20°C and that the apparent activation energy for the conversion was about 18 kcal/mol. The other two immunosuppressants, cyclosporin C and D, were also shown to undergo interconversion. This kinetic analysis of the interconversion should be helpful in clarifying the relationship between molecular structure and activity of the immunosuppressants.
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    Determination of carbendazime in lettuce samples by SFE-HPLC (1994)
    Springer
    Chromatographia 38 (1994), S. 395-399 
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    ISSN: 1612-1112
    Keywords: Supercritical fluid extraction ; Column liquid chromatography ; Carbendazime analysis ; Vegetable samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An SFE-HPLC method for the determination of carbendazime in lettuce leaves is described. The method involves a prior lyophilization of the sample and subsequent extraction with supercritical carbon dioxide containing methanol. The extraction conditions are as follows: amount of lyophilized sample, 1 g; CO2 density, 0.75 g/ml; temperature, 50 °C; flow-rate, 1.8 ml/min; dynamic extraction time, 25 min. Carbendazime is determined with an octadecylsilane column, an acetonitrile/water 30∶70 mobile phase and fluorescence detection at 285/317 nm. Carbendazime recoveries from spiked samples were all close to 100%. A comparison with the results from a conventional method for the determination of carbendazime reveals the new method to be more rapid, simple and reproducible for samples with low concentrations of analyte.
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    A photometric flow measurements method for characterisation of HPLC pumps (1994)
    Springer
    Chromatographia 38 (1994), S. 421-430 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pumps ; Flow control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The measurement of flow constancy and pulsation amplitudes of HPLC pump based on the photoconversion of malachite green leucocyanide is described. The irradiation time and hence the degree of conversion of the leucocyanide is correlated to flow fluctuations of piston driven HPLC pumps. It is possible to measure the amplitude of pulsations and determine the constancy of the flow rate. Most of the pumps show a flow stability better than ±1% measured as relative standard deviation of the flow rate under HPLC conditions (pressure drop 100 bar at 1 ml/min flow rate). The most expensive pump of those tested showed less than ±0.5% flow instability, however, this result was achieved by installation of a large-volume pulsation damper. The method described also allows flow rate measurements under FIA conditions where there is little or no pressure drop at the pump outlet.
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    Surface modification by calcium ions—Effect on chromatographic properties of silica (1994)
    Springer
    Chromatographia 39 (1994), S. 29-34 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calcium modified silica ; Calcium adsorption isotherms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The modification of silica surfaces by calcium ions has been studied by high-performance liquid chromatography. After treatment at pH 7.0 and 9.0 with calcium hydroxide, the modified silicas were characterised by physical and chemical analysis. From measurements by atomic absorption, the amount of calcium adsorbed was 650 ppm on silica modified at pH 7.0, and 4800 ppm on silica modified at pH 9.0. The amount of calcium on the modified silica was 0.574 groups nm−2 at pH 9.0 (original silica: mean pore diameter 176 Å, specific surface 279 m2 g−1, pore volume 1.23 ml g−1, mean particle size 9.8 μm). On the other hand, the amount of calcium in the original silica was 58 ppm. The separation factor, α for N-methylaniline and N,N-dimethylaniline was 5.2 on silica modified at pH 9.0, but could not be measured on silica modified at pH 7.0 and the original silica, using iso-propyl alcohol—n-hexane (0.5∶99.5) eluent.
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    Dual injector solvent elution and focussing technique for the on-line analysis of solid-phase extraction cartridges in HPLC (1994)
    Springer
    Chromatographia 39 (1994), S. 45-50 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sample preconcentration ; Solid-phase extraction ; Solvent focussing ; Injection techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new dual injector solvent focussing and elution technique developed for high-performance liquid chromatography (HPLC) greatly improves chromatographic efficiency for the on-line analysis of C18 solid-phase extraction (SPE) cartridges. Solutions containing three benzene homologs were used to characterize the dual injector analysis technique and to compare the chromatographic efficiency of this method with conventional SPE analysis methods. Sampling was performed off-line using a glass precolumn cartridge (3 mm i.d. × 30 mm) packed with 15–35 μm C18 silica. On-line cartridge analysis was achieved with two injection valves in either serial or parallel configuration. The injection loop of the first valve contains the eluting solvent, and the cartridge holder is connected in place of the injection loop of the second valve. When an injection is made, both valves are turned to the inject position, and the solvent plug is forced through the cartridge, focussing the analyte at the solvent front as it elutes the cartridge. Solvent focussing at the head of the column, resulting from preconditioning of the column with a small plug of water during injection, further minimizes the variance of the injection plug and improves the chromatographic efficiency. The technique has potential applications to environmental and biological fluid analysis where analyte preconcentration and resolution from the sample matrix components may be difficult with current SPE methods.
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    An improved method for the determination of free sphingosine in serum (1994)
    Springer
    Chromatographia 39 (1994), S. 85-90 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Carbopack B ; Free sphingosine in human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid, sensitive and selective high-performance liquid chromatographic method has been developed for the determination of sphingosine in human serum. After precipitation with methanol, the samples were extracted using Carbopack B disposable columns; the sphingosine was eluted with 0.05 M hydrochloric acid in methanol-dichloromethane (20∶80, v/v) and the extract evaporated to dryness at 40°C. The sample residue was then reconstituted with methanol and reacted with o-phthaldialdehyde reagent to produce a fluorescent compound. Separation was performed using an LC-18 column with 0.05 M phosphate buffer (pH 7)-methanol-acetonitrile (15∶80∶5, v/v) as mobile phase. Fluorescence detection was performed with excitation and emission wavelengths of 340 and 455 nm, respectively. The serum extract was re-analyzed with a cyano LC column to minimize the possibility of false positive results. The possible interference of compounds having a structure similar to that of sphingosine was evaluated. The mean recovery of sphingosine was 〉94.5%. The limit of detection of the assay was 1 ng mL−1. The between-run and within-run coefficients of variation for replicate analyses were 〈4.0% and 〈3.4%, respectively. The levels of free sphingosine in the serum of 40 normal subjects (20 male and 20 female) was investigated; the average level was 81.6±41.1 ng mL−1 (mean ±S.D.) for males and 85.5±33.7 ng mL−1 for females.
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    URL: http://dx.doi.org/10.1007/BF02320464
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    Analysis of thiamine in dried yeast by high-performance liquid chromatography and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (1994)
    Springer
    Chromatographia 39 (1994), S. 91-96 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Atmospheric pressure chemical ionization-mass spectrometry ; Dried yeast ; Thiamine ; Ion-pair extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatography (HPLC) and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS) have been applied to the analysis of thiamine in dried yeast. Thiamine was extracted from dried yeast with isobutanol containing sodium 1-octanesulfonate as an ion-pairing agent and determined by HPLC on a reversed phase ODS column with UV detection at 254 nm. Response was linear in the range 25–300 μg/g of thiamine in dried yeast with a coefficient of variation in the reproducibility of 8.0%. Thiamine was recovered in good yield (109.2%, n=5). Identification of the thiamine peak was obtained by the mass spectrum using the HPLC/APCI-MS system. The utility of the selected ion monitoring technique using the HPLC/APCI-MS was also investigated. The results obtained by this method are in good agreement with those obtained by the thiochrome method [1].
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    An improved high-performance liquid chromatographic determination of chlorpropamide in human plasma (1994)
    Springer
    Chromatographia 39 (1994), S. 107-109 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Drug assay ; Chlorpropamide ; Tolbutamide ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Samples were extracted with dichloromethane and the organic layer evaporated to dryness. The residue was dissolved in methanol, and 10 μl aliquot injected onto the column. Tolbutamide was used as the internal standard for chlorpropamide. The UV detector response was linear over the range 0–200 μg ml−1 with a correlation coefficient of 0.999; detection limit: 0.002 μg ml−1. Within-day and between-day assay variation was generally ≤7%. No interference from endogenous constituents was observed. The utility of the method was demonstrated by determining chlorpropamide in samples from six healthy volunteers following a single oral dose of 250 mg. The procedure is simple and requires small volumes of plasma.
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    URL: http://dx.doi.org/10.1007/BF02320468
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    The modiffication of alumina, zirconia, thoria and titania for potential use as HPLC stationary phases through a silanization/hydrosilation reaction scheme (1994)
    Springer
    Chromatographia 39 (1994), S. 649-654 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases ; Non-silica based supports ; Hydrosilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A process for bonding a monolayer of silane to the surface of alumina, zirconia, thoria and titania by reaction with the hydrolysis product of triethoxysilane is described. The hydride containing material is then further reacted with a terminal olefin in the presence of a platinum catalyst to produce a chemically modified oxide surface which could be used as a chromatographic stationary phase. The success of this reaction is monitored by diffuse reflectance infrared Fourier transform and cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy as well as by differential scanning calorimetry. On all four oxides both the hydride intermediate and the alkyl bonded product are successfully formed via the silanization/hydrosilation reaction sequence.
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    Studies of some experimental conditions for the polymerization of the continuous beds (cross-linked polyacrylamide gels) in order to improve their chromatographic properties (1994)
    Springer
    Chromatographia 39 (1994), S. 655-662 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Continuous beds ; Compressed beds ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Continous chromatographic beds are synthesized by a simple and cost-effective procedure which does not involve the conventional, time-consuming preparation of beads. The aim of this study was to improve the flow properties of the beds by investigating how they are affected by polymerization temperature, the pH of the buffer in which the polymerization takes place, the nature of the constituents of this buffer, the concentrations of catalyst and accelerator and the concentration of the precipitating agent (ammonium sulfate). The infuence of flow rate and the time constants of the detector and recorder on peak width was also studied.
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    URL: http://dx.doi.org/10.1007/BF02274579
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    Reversed phase C18 packings for the separation of polycyclic aromatic hydrocarbons by high performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 668-672 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Monomeric and oligomeric RP packings ; Preparation of RP stationary phases ; Polycyclic aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The preparation of C18 stationary phases for the separation of polycyclic aromatic hydrocarbons has been investigated. The effect of the pore size of the silica, the endcapping procedure, the amount of reagent and the amount of water in the preparation was also examined. A good correlation between surface coverage and capacity factor was found. The maximum surface coverage available with our preparation method lies between 3–3.5 μmol m−2, slightly depending on the pore size of the silica. Oligomeric not endcapped C18 packing materials are optimal for the separation of polycyclic aromatic hydrocarbons.
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    URL: http://dx.doi.org/10.1007/BF02274581
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    Estimation of phenolic compounds in green pepper berries (Piper nigrum L.) by high-performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 743-746 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Green pepper berries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method is described for the separation and estimation of phenolic compounds in six commercial varieties of green pepper berries. Among these, two phenolic compounds namely 3,4-dihydroxyphenylethanol glucoside and 3,4-dihydroxy-6-(N-ethyl amino)benzamide that served as efficient substrates for pepper phenolase, showed wide qualitative and quantitative variation in their composition within the varieties. Quantitative estimations of these two compounds were carried out using 4-methylcatechol and epinephrine as external standards. This method is suitable for the estimation of phenolic compounds in green pepper berries in one run.
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    URL: http://dx.doi.org/10.1007/BF02274592
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    Analysis of basic hair dyes by HPLC with on-line post-column photochemical derivatisation (1994)
    Springer
    Chromatographia 39 (1994), S. 138-145 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode array detection ; Post-column photochemical derivatisation ; Hair dyes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase liquid chromatographic method is proposed for the analysis of basic hair dyes (raw materials and colourant formulations). The performance of the method was enhanced by introducing post-column on-line photochemical derivatisation in combination with a Diode Array Detector. On-line photoderivatisation provided an effective way of selectively transforming the analytes to compounds with different spectral properties. For each analyte two characteristic UV-Visible spectra (photoreactor on and off) were obtained with the same mobile phase and this information in combination with the chromatographic data (k' at pH 3.0 and 4.5) enabled the unambiguous identification of both commonly used, approved, and banned basic hair dyes. Additionally, this approach was found useful to improve the method sensitivity, allowing the determination of analytes present in low concentration (0.03%) in complex commercial formulations.
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    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 4. Sudden-transition gradient elution of styrene/ethyl methacrylate copolymers in reversed phase mode (1994)
    Springer
    Chromatographia 39 (1994), S. 170-174 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/ethyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and ethyl methacrylate have been separated according to composition byn-heptane gradients on a C18 bonded phase after injection into acetonitrile and subsequent sudden transition to a concentration of either dichloromethane or tetrahydrofuran between 30 and 50% or 20 and 50%, respectively. Acetonitrile is a polar non-solvent for the copolymers under investigation and ensures proper retention of the samples on a non-polar stationary phase. Dichloromethane and tetrahydrofuran are good solvents of moderate polarity. The addition of, e.g., 30 vol% of one of these solvents increased the dissolution power of the starting eluent but not to the extent necessary for elution. The latter was achieved by the addition ofn-heptane, which is a non-solvent for the polymers investigated. Thus, its eluting power must be understood as the consequence of its modifying effect on the polarity of the eluent mixture. The higher the content of copolymer in ethyl methacrylate the earlier it was eluted. Since acetonitrile andn-heptane are only partly miscible, phase diagrams were measured after the addition of either tetrahydrofuran or dichloromethane as a third component. Homogeneous mixtures were obtained on addition of about 30% solvent (one of both of the latter).
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    On-line trace enrichment — column liquid chromatography of polar pollutants in surface water using bifunctional membrane-based extraction-disk cartridges (1994)
    Springer
    Chromatographia 39 (1994), S. 239-245 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Membrane-extraction disks ; On-line trace enrichment ; Polar pollutants ; Surface water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An on-line trace-enrichment system, using a bifunctional membrane extraction-disk cartridge, has been combined with a column liquid chromatography separation for the simultaneous determination of basic, neutral and acidic pollutants in surface water. The enrichment device consisted of a specially constructed holder containing both C-18 and cation-exchange disks. The holder can contain up to 25 disks of 0.5 mm thickness and 4.6 mm diameter. Before trace enrichment of 20 ml of surface water (pH 3.0), calcium ions were removed from the sample by means of an oxalic acid precipitation. Desorption of the cartridge was at elevated temperature using reversed-phase gradient elution; detection was performed with a diode-array UV absorbance detector. The detection limits for the test compounds in surface water are typically 0.5–2 μg/l; the calibration graphs are linear from the lower limit of determination up to 50 μg/l.
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    Retention characteristics of fluorinated bonded silica phase in reversed-phase liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 285-293 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluorinated chemically bonded silica ; Aromatic compounds ; Molecular shape vs. retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorinated bonded silica has been evaluated as a packing material in reversed-phase liquid chromatography (RPLC) with polycyclic aromatic hydrocarbons, chlorinated benzenes and substituted benzenes as sample probes. The bonded material is useful as a reversed-phase stationary phase and for polar compounds it offers a specific selectivity not found with octadecylsilica (ODS) phases. The phase also retains non-planar compounds more than planar molecules. The results can be explained by conformational differences between ODS and the fluorinated bonded phase by MM2 calculation.
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    Optimization of mobile phases for HPLC of cis-trans carotene isomers (1994)
    Springer
    Chromatographia 39 (1994), S. 346-354 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α-Carotene cis-isomers ; β-Carotene cis-isomers ; Polymer stationary phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various methanol-based, binary and ternary solvent systems were compared with respect to resolution of cis isomers of α and β-carotene by reversed-phase HPLC. A ternary system: acetonitrile-methanol-methylene chloride (75∶15∶10), or a binary system: acetonitrilemethanol (90∶10 or 5∶95) provided the best separation of β-carotene and its four cis isomers, 9-cis, 13-cis, 15-cis and 13,15-di-cis-β-carotene. The elution order of 9-cis and 13-cis-β-carotene was dependent on the methanol concentration. Methanol-methylene chloride (99∶1) resolved α-carotene and its three cis isomers, 9-cis, 13-cis, and 15-cis-α-carotene. It also proved the best for simultaneous separation of cis isomers of α and β-carotene. Sample solvent can affect the separation efficiency of each isomer. The presence of cis isomers of α and β-carotene in fresh and cooked carrots was also determined.
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    Chromatographic determination of D-amino acids as native constituents of vegetables and fruits (1994)
    Springer
    Chromatographia 39 (1994), S. 419-426 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chirasil-Val ; Amino acid enantiomers ; N-Isobutyryl-cysteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Free D-amino acids (D-AA) were detected as native constituents in juices of vegetables (cultivars of cabbage, tomato, carrot, garlic) and fruits (organes, clementine, grapefruit, lemon, apples, pear, grapes) using gas chromatography (GC) or high-performance liquid chromatography (LC). For investigation by GC, AA enantiomers were converted into theirN(O)-pentafluoropropionyl 2-propyl esters and resolved on a Chirasil-L-Val capillary column. For determination by LC, precolumn derivatization of AA enantiomers usingo-phthaldialdehyde together with the chiral thiolsN-isobutyryl-L-cysteine orN-isobutyryl-D-cysteine and fluorescence detection of the diastereomeric isoindole derivatives, resolvable on an octadecylsilyl stationary phase, were used. D-Ala (0.6–3.8%) was detected in all freshly pressed plant juices usually in the highest relative amounts. Other D-AA detected were D-Asx (0.1–1.9%), D-Glx (0–1.3%), D-Ser (0–1.7%), D-Arg (0.4–1.2%, in grapes, orange, grapefruit, and clementine) and D-Leu and D-Val (1% in cabbage). Absolute amounts of native D-AA were totally 28–57 μmol L−1 in fruit juices, 14.5 μmol L−1 in a tomato juice and 8.5 μmol L−1 in a carrot juice.
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    Temperature effect in separation of fullerene by high-performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 453-459 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fullerenes ; Octadecylsilicas ; Temperature effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of column temperature, especially at low temperatures, on the separation of fullerenes on monomeric and polymeric octadecyl silica (ODS) bonded phases has been studied. Decreasing the column temperature induces an increase in selectivity. The best temperature for the separation of fullerenes was determined for both types of ODS phase with n-hexane eluent. The selectivity for higher fullerenes on monomeric phases becomes similar to that on polymeric phases to low temperature. It has been found that as the carbon content of monomeric phases is increased, the selectivity also becomes similar to polymeric phases.
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    A chromatographic and chemometric study of the bark phenolic compounds of two poplar clones with different resistance toDiscosporium populeum (1994)
    Springer
    Chromatographia 39 (1994), S. 481-489 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Poplar bark ; Discosporium populeum infection ; Chemometric data evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase high performance liquid chromatography with diode array detection was used to analyze phenolic compounds contained in bark extracts of two different poplar clones known to have different resistance toDiscosporium populeum infection. Statistical treatments both monovariate and multivariate were applied to the results in order to identify regularities useful to discriminate the polar resistance and to check the importance of seasonal and cultivation site related factors. For the two clones examined phenolic compounds showed great discrimination ability not influenced by either sample collection period or cultivation site.
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    URL: http://dx.doi.org/10.1007/BF02278766
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    Determination of catecholamines in urine by micellar liquid chromatography with coulometric detection (1994)
    Springer
    Chromatographia 39 (1994), S. 591-596 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid chromatography ; Catecholamines in urine ; Coulometric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The determination of catecholamines by HPLC with a sodium dodecyl-sulphate (SDS), micellar mobile phase on a C18 column and with coulometric detection was studied. The eluate was conditioned at +0.25 and +0.00 V, and the current at −0.16V was recorded. A previously developed model which describes the chromatographic behaviour of solutes in HPLC with hybrid, micellar mobile phases was used to optimize the SDS and ethanol concentrations. A mobile phase of 0.15M SDS in a phosphate buffer of pH 3.4 and without ethanol is recommended. The limits of detection were 0.4–0.7 ng ml−1. The procedure was applied to the determination of unconjugated L-dopa, norepinephrine and dopamine in urine. Direct injection of the urine samples gave high results but the unconjugated catecholamines could be determined with a single solid-phase extraction step on an alumina column.
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    Improved separation of diastereoisomers in capillary electrophoresis using a mixture of β-cyclodextrin and sodium taurodeoxycholate (1994)
    Springer
    Chromatographia 39 (1994), S. 627-630 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar electrokinetic capillary electrophoresis ; Tetrahydrocarbazole derivatives ; β-Cyclodextrin ; Taurodeoxycholate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 2,3,4,6-tetra-O-acetyl-β-D-glucopranosyl isothiocyanate derivatives of a number of basic compounds, containing one chiral center, have been prepared. The indirect resolution of enantiomers was achieved with a high separation efficiency by capillary electrophoresis, using a sodium taurodeoxycholate/β-cyclodextrin system. This methodology was found to be superior to the resolution of the same derivatives by reversed phase HPLC analysis. A possible mechanism for stereoselectivity is described.
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    The quiescent center in roots of maize: initiation, maintenance and role in organization of the root apical meristem (1994)
    Springer
    Protoplasma 183 (1994), S. 100-106 
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    ISSN: 1615-6102
    Keywords: Auxin ; Meristem (root) ; Quiescent center ; Root cap ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using roots of maize, we tested the hypothesis that the origin and maintenance of the quiescent center (QC) are a consequence of polar auxin supply. Exposing roots to the polar auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA), or to low temperature (4 °C, with subsequent return to 24 °C), enhances mitotic frequency within the QC. In both treatments, the QC most typically is activated at its distal face, and the protoderm/dermatogen undergoes several periclinal divisions. As a result, the root body penetrates and ruptures the root cap junction and the characteristic “closed” apical organization changes to “open”. A QC persists during these changes in apical organization, but it is diminished in size. The data from the TIBA-treated roots suggest a role for auxin in the origin and maintenance of the QC, and further, that alterations in QC dimensions are a consequence of polar auxin supply. We hypothesize that the root cap, and specifically the root cap initials, are important in regulating polar auxin movements towards the root apex, and hence are important in determining the status of the QC.
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    Iron deprivation in cyanobacteria (1994)
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    Journal of applied phycology 6 (1994), S. 199-210 
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    ISSN: 1573-5176
    Keywords: cyanobacteria ; iron deficiency ; photosynthesis ; siderophores ; flavodoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron is an essential component of electron transport in almost all living organisms. It is particularly important to phototrophs like cyanobacteria because 22–23 irons are required for a complete functional photosynthetic apparatus. Since the low solubility of Fe+++ above neutral pH in oxic ecosystems severely limits the biological availability of iron to aquatic microorganisms, cyanobacteria and other microbes have developed a number of responses to cope with iron deficiency. Cyanobacterial responses to iron stress include the synthesis of an efficient, siderophore-based system to scavenge iron and the substitution of ferredoxin with flavodoxin. An additional response in cyanobacteria involves the alteration of the light-harvesting apparatus that includes the appearance of a new, iron-stress-induced, photosystem II, chlorophyll-binding protein. Although cytochromec-553 has a potential non-iron-containing replacement in plastocyanin, a copper-containing protein, iron stress appears to favor the utilization of cytochromec-553 because siderophores also bind copper and form a complex that is excluded from the cell. This paper is intended primarily as a review of molecular and physiological responses of actively growing cyanobacterial cultures to conditions of iron stress, where iron is present but essentially insoluble, and to differentiate these responses from iron starvation, where the amount of iron in the system is not sufficient for cell growth.
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    Use of chlorophyll fluorescence to estimate the effect of photoinhibition in outdoor cultures ofSpirulina platensis (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 31-34 
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    ISSN: 1573-5176
    Keywords: fluorescence ; photoinhibition ; photosynthesis ; Spirulina ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorophyll fluorescence measurements were used to evaluate the effect of temperature on photoinhibition inSpirulina platensis cultures grown in tubular reactors outdoors. Cultures grown at 35 °C during the day time showed a lower reduction in the Fv/Fm ratio as compared to cultures grown at 25 °C. It is demonstrated that the lower temperature photoinhibited cells can undergo a complete recovery once transferred to low light and higher temperature. This recovery does not take place when 100 µg ml-1 chloramphenicol is added to cells. The recovery is light dependent and cells incubated in the dark at low temperature do not show a recovery in the Fv/Fm ratio. The data presented strongly support the hypothesis that photoinhibition takes place in outdoorSpirulina cultures. At the same time it is demonstrated that fluorescence measurements can be used as a fast reliable indication for photoinhibition in outdoor algal cultures.
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    Use of macroalgae for marine biomass production and CO2 remediation: a review (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 45-60 
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    ISSN: 1573-5176
    Keywords: biofilter ; biofuels ; CO2 ; macroalgae ; marine biomass ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biomass production from macroalgae has been viewed as important mainly because of the need for pollution abatement. Environmental considerations will increasingly determine product and process acceptability and drive the next generation of economic opportunity. Some countries, including Japan, are actively promoting "green" technologies that will be in demand worldwide in the coming decades. Should an international agreement on CO2-reduction be ratified, its effective use for energy production would be of high priority. This report shows that macroalgae have great potential for biomass production and CO2 bioremediation. Macroalgae have high productivity, as great or greater than the most productive land plants, and do not compete with terrestrial crops for farm land. The review focuses on recent data on productivity, photosynthesis, nutrient dynamics, optimization and economics. Biomass from macroalgae promises to provide environmentally and economically feasible alternatives to fossil fuels. Nevertheless, the techniques and technologies for growing macroalgae on a large-scale and for converting feedstocks to energy carriers must be more fully developed.
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    What kind of lamp for the cultivation of algae? (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 309-313 
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    ISSN: 1573-5176
    Keywords: light source ; emission spectrum ; photosynthesis ; algae ; absorption ; efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method for quantitative evaluation of light sources from the point of their suitability for algal cultivation is described. Two parameters are used for the evaluation: (1) amount of photons emitted in the spectral region absorbed by algae per consumed unit of electrical energy; (2) fraction of photons intercept by the algae that got effectively transformed into chemical energy. The value of parameter (2) depends on the emission spectrum of the light source, the absorption spectrum of the algae, quantum capacity of the algae and on conditions of cultivation. The method permits the assessment of the differences in algal productivity under light of various light sources with respect to other recent methods for comparison.
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    Turbulence in mass algal cultures and the role of light/dark fluctuations (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 331-335 
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    ISSN: 1573-5176
    Keywords: turbulence ; photosynthesis ; Chlorella ; light/dark cycles ; mass transfer rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In mass algal cultures, some form of agitation is usually provided; among other effects, this moves the organisms though an optically dense profile and provides mixing. During this transport, medium frequency fluctuations in the light energy supply are perceived by the algae, which are of the order of 1 Hz and less. It has been suggested that turbulence with the resultant light/dark cycles of medium frequency enhances productivity. However, turbulence has two major influences in a well mixed system: it facilitates fluctuating light regimes and increases the transfer rates between the growth medium and the cultured organism. An estimation of productivity as oxygen liberation was measured under laminar and turbulent flow rates, and varying light/dark ratios. Increased turbulence, which increased exchange rates of nutrients and metabolites between the cells and their growth medium, together with increased light/dark frequencies, increased productivity and photosynthetic efficiency.
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    Isolation and characterization of a maize gene encoding chalcone flavonone isomerase (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 1-8 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Flavonoid biosynthesis ; P gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report here the first cloning of a chalcone flavonone isomerase gene (CHI) from maize. Northern blot experiments indicate that the maize CHI gene (ZmCHI1) is regulated in the pericarp by the P gene, a myb homologue. The ZmCHI1 gene encodes a 24.3 kDa product 55% and 58% identical to CHI-A and CHI-B from Petunia, respectively. This maize CHI gene has four exons and an intron-exon structure identical to the CHI-B gene of Petunia hybrida. RFLP mapping data indicate that some inbred lines contain two additional CHI-homologous sequences, suggesting an organization more complex than that found in Petunia or bean. The possibility that the additional CHI-homologous sequences are responsible for the lack of CHI mutants in maize will be discussed.
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    URL: http://dx.doi.org/10.1007/BF00277341
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    Soil core and minirhizotron comparison for the determination of root length density (1994)
    Springer
    Plant and soil 161 (1994), S. 225-232 
    Details
    ISSN: 1573-5036
    Keywords: minirhizotron ; root-length density ; soil core ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Detailed knowledge of the distribution of roots in the soil is important in understanding the extraction of water and nutrients from soil. Various techniques have been developed to monitor root-length density under field conditions. Excavation techniques, including soil cores, have long been considered to give reliable estimates of root-length density, but these techniques are laborious in sample collection and tedious in determination of root lengths. An attractive alternative for monitoring root-length density has been the minirhizotron whereby a periscope is inserted into a clear tube permanently installed in the soil for repeated and rapid measures of root development. The objective of this study was to compare the ability of the minirhizotron technique to measure root-length density as compared to the root-core technique. As in previous studies, substantial disagreement existed between the two techniques in the top 30-cm of the soil. The results from the minirhizotron consistently indicated a much lower root population than the root-core technique in the surface layer of soil. This is especially worrisome because more than 45% of the root-length density was found in this layer with the root-core technique. At deeper soil layers, the minirhizotron data proved to be no less variable than the root-core technique making the determination of statistically significant results difficult. Finally, the relationship between the minirhizotron and soil-core results varied with time even when the observations from the soil surface layer were ignored. Attempts to directly translate minirhizotron observations into a root-length density using a correlation approach would be suspect based on the results of this experiment.
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    URL: http://dx.doi.org/10.1007/BF00046393
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    Genetic variation in pigeon pea (Cajanus cajan (L.) Mill sp.) in response to successive cycles of water stress (1994)
    Springer
    Plant and soil 158 (1994), S. 193-201 
    Details
    ISSN: 1573-5036
    Keywords: photosynthesis ; osmotic adjustment ; stomatal conductance ; relative water content ; water potential ; water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Four pigeon pea [Cajanus cajan (L.) Mill sp.] cultivars were studied during two cycles of development of water stress and recovery. During these two cycles the genetic variation in vegetative development, leaf water potential, relative water content, photosynthesis, and stomatal conductance was followed. Plants were grown in a greenhouse and irrigated every seventh day. On two occasions (30 days and 80 days from sowing) water was withheld for 13 days in one group of plants and 16 days in another. Control plants were irrigated as usual. The four cultivars differed in their response to drought, with ICPL 215 being the most tolerant cultivar. In the plants exposed to the 13-day water stress, the first stress cycle resulted in preconditioning of plants such that higher values for carbon dioxide exchange rate and relative water content were observed in the second stress cycle. The longer stress period (16 days) resulted in some damage to the photosynthetic capacity and in a slow recovery rate in both cycles. During the second drought cycle the plants retained a water content above the critical value, possibly due to osmotic adjustment. It seems that water status parameters, especially relative water content, may serve as indicators of drought tolerance in pigeon pea varieties and may be useful in breeding programs for cultivation of pigeon pea under semiarid conditions.
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    URL: http://dx.doi.org/10.1007/BF00009494
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    Contributions of the surface of the root tip to the growth of Zea roots in soil (1994)
    Springer
    Plant and soil 165 (1994), S. 315-321 
    Details
    ISSN: 1573-5036
    Keywords: cell wal's ; epidermis ; growth ; root development ; soil penetration ; stiffness ; Zea diploperennis ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The development of the epidermal layer of roots of Zea is traced from the quiescent centre to the zone where root hairs develop. In the zone of cell division a three layered coat forms on the outside of the epidermal cells consisting of the outer epidermal walls, overlaid by a two-layered pellicle composed of a thick fibrillar inner layer of polysaccharide, and a thin fibrillar outer layer of protein. The epidermal cells divide several times in the same longitudinal file but rarely across a radius to give a new longitudinal file. Thus, the radial walls become much thicker than all but the original transverse walls, and packets of up to 32 daughter cells derived from a single initial may be distinguished. The pellicle develops during these divisions as a continuum over the outer walls of the daughter cells. It is proposed that the pellicle provides a stiffening to the forward end of the root which permits it to penetrate soil without bending. Support for this hypothesis is shown by the Zea mays mutant Ageotropic in which the pellicle is absent, the epidermal surface is disorganized, and which grows crookedly through soil. In the zone of extension growth of normal roots of two Zea species the pellicle thins and disappears. Circumferential strips of the pellicle were peeled off the young epidermal cells and could be stretched to twice their length. This deformation is partly the result of the pellicle stretching and breaking above the attachments of the radial walls. After normal thinning of the pellicle, detachment of the radial walls at their outer ends produces a corrugated surface in the proximal zone of the root tips. In dicotyledons (e.g., soybean), there is no similar pellicle, but a stiff root tip is produced by a long multi-layered root cap, the proximal portion of which covers the elongating epidermal surface.
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    URL: http://dx.doi.org/10.1007/BF00008075
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    Comparison of selective agents for use with the selectable marker gene bar in maize transformation (1994)
    Springer
    Plant cell, tissue and organ culture 36 (1994), S. 1-7 
    Details
    ISSN: 1573-5044
    Keywords: bialaphos ; glufosinate ; phosphinothricin ; l-proline ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effectiveness of four phosphinothricin (PPT)-based selective agents were evaluated for use in maize transformation: glufosinate, bialaphos, Basta® and Herbiace®. Glufosinate and its commercial formulation, Basta®, were less effective in controlling growth of non-transgenic corn callus than the tripeptide, bialaphos, or its commercial formulation, Herbiace®. Addition of 25 mM l-proline had no significant effect on selection when using bialaphos. However, when l-proline was included with the selective agent glufosinate, selection was inhibited and callus growth was enhanced. At four weeks, callus growth on 0.3, 1.0 and 3.0 mg l-1 glufosinate in the presence of proline was 76, 43, and 21% of control growth, respectively, and in the absence of proline was only 32, 9, and 6% of control growth. Optimized selection protocols for Basta® and bialaphos yielded comparable numbers of transformants. Using these protocols, fertile transgenic plants were regenerated from transformed callus cultures.
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    URL: http://dx.doi.org/10.1007/BF00048308
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    Genetic and environmental effects on abscisic acid accumulation in leaves of field-grown maize (1994)
    Springer
    Euphytica 78 (1994), S. 81-89 
    Details
    ISSN: 1573-5060
    Keywords: abscisic acid ; inheritance ; drought stress ; Zea mays ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study analyzes the components of phenotypic variation for abscisic acid (ABA) content in maize (Zea mays L.) leaves and the correlations with drought sensitivity index (DSI) and silk delay (SD), involved in the reaction to water deficit. Eight early- and seven medium-maturity inbreds were examined in field trials: in 1990 with low irrigation volume and in 1991 with low and high irrigation volumes. ABA concentration and DSI were investigated at growth stages (S) corresponding to stem elongation (S3), appearance of the first husks (S4), and mid-end of silking (S5). The ABA concentration was significantly higher in conditions of water deficit and in the later growth stage. The genetic component for ABA concentration attained higher relative values than those shown by DSI in the same growth stages and by SD; moreover, it increased from growth stage 3 to stage 5. The genotype × year and genotype × irrigation volume interactions were smaller for ABA concentration than for DSI and SD. The broad sense heritability on a plant basis, estimated in drought conditions, for ABA concentration ranged from 21.4 to 55.1% according to maturity group and growth stage. A wide variation was observed among lines for ABA concentration: the medium-maturity group showed a three-fold range (from 219 to 605 ng ABA g−1 dry weight). No clear relationships between ABA concentration, DSI and SD were found. These results indicate the feasibility of a selection for ABA concentration within segregating populations derived from crosses between the inbred lines herein tested.
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    URL: http://dx.doi.org/10.1007/BF00021401
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    Model studies of chlorophyll fluorescence reabsorption at chloroplast level under different exciting conditions (1994)
    Springer
    Photosynthesis research 40 (1994), S. 67-74 
    Details
    ISSN: 1573-5079
    Keywords: light conditions ; theoretical model ; barley leaf ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A theoretical model is presented describing the distortion of chlorophyll fluorescence spectra of a chloroplast or a group of chloroplasts by the effect of fluorescence reabsorption. Model calculations using the experimental data show that the primary reabsorption effect occurs already within one chloroplast and the spectral distortion depends significantly on the excitation regime of the chloroplast. A theoretical dependence of the distortion function, defined as a change in the F(685)/F(735) fluorescence band ratio, on the mean chlorophyll concentration in a chloroplast is predicted for different light excitation regimes. The distortion of measured chlorophyll fluorescence spectra at 77 K of chloroplast suspension adsorbed on filter papers of two strongly different diffusive reflectivities and at different mean chlorophyll concentrations are discussed with the help of the presented theory.
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    URL: http://dx.doi.org/10.1007/BF00019046
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    UV-B damage and protection at the molecular level in plants (1994)
    Springer
    Photosynthesis research 39 (1994), S. 475-489 
    Details
    ISSN: 1573-5079
    Keywords: DNA repair ; flavonoids ; gene expression ; oxidative stress ; photosynthesis ; promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Influx of solar UV-B radiation (280–320 nm) will probably increase in the future due to depletion of stratospheric ozone. In plants, there are several targets for the deleterious UV-B radiation, especially the chloroplast. This review summarizes the early effects and responses of low doses of UV-B at the molecular level. The DNA molecules of the plant cells are damaged by UV due to the formation of different photoproducts, such as pyrimidine dimers, which in turn can be combatted by specialized photoreactivating enzyme systems. In the chloroplast, the integrity of the thylakoid membrane seems to be much more sensitive than the activities of the photosynthetic components bound within. However, the decrease of mRNA transcripts for the photosynthetic complexes and other chloroplast proteins are among very early events of UV-B damage, as well as protein synthesis. Other genes, encoding defence-related enzymes, e.g., of the flavonoid biosynthetic pathway, are rapidly up-regulated after commencement of UV-B exposure. Some of the cis-acting nucleotide elements and trans-acting protein factors needed to regulate the UV-induced expression of the parsley chalcone synthase gene are known.
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    Photosynthetic electrogenic events in native membranes ofChloroflexus aurantiacus. Flash-induced charge displacements within the reaction center-cytochromec 554 complex (1994)
    Springer
    Photosynthesis research 41 (1994), S. 135-143 
    Details
    ISSN: 1573-5079
    Keywords: photosynthesis ; electrometry ; membrane potential ; electron transfer ; charge displacement ; electrostatic ; Chloroflexus aurantiacus ; Rhodopseudomonas viridis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The thermophilic phototrophChloroflexus aurantiacus possesses a photosynthetic reaction center (RC) containing a pair of menaquinones as primary (QA) and secondary (QB) electron acceptors and a bacteriochlorophyll dimer (P) as a primary donor. A tetraheme cytochromec 554 with two high(H)- and two low(L)-potential hemes operates as an immediate electron donor for P. The following equilibrium Em,7 values were determined by ESR for the hemes in whole membrane preparations: 280 mV (H1), 150 mV (H2), 95 mV (L1) and 0 mV (L2) (Van Vliet et al. (1991) Eur. J. Biochem. 199: 317–323). Partial electrogenic reactions induced by a laser flash inChl. aurantiacus chromatophores adsorbed to a phospholipid-impregnated collodion film were studied electrometrically at pH 8.3. The photoelectric response included a fast phase of ΔΨ generation (τ 〈 10 ns, phase A). It was ascribed to the charge separation between P+ and QA − as its amplitude decreased both at high and low Eh values (Em,high=360±10 mV, estimated Em,low∼\s-160 mV) in good agreement with Em values for P/P+ and QA/QA − redox couples. A slower kinetic component appeared upon reduction of the cytochromec 554 hemes (phase C). With H1 reduced before the flash the amplitude of phase C was equal to 15–20% of that of phase A and its rise time was 1.2–1.3 μs: we attribute this phase to the electrogenic electron transfer from H1 to P+. Pre-reduction of H2 decreased the τ value to about 700–800 ns and increased the amplitude of phase C to 30–35% of that of phase A. Pre-reduction of L1 further accelerated phase C (up to τ of 500 ns) and induced a reverse electrogenic phase with τ of 12 μs and amplitude equal to 10% of phase A. Upon pre-reduction of L2 the rise time of phase C was decreased to about 300 ns and its amplitude decreased by 30%. The acceleration in the onset of phase C is explained by the acceleration of the rate-limiting H1 ⇒ P electrogenic reaction after reduction of the other hemes due to their electrostatic influence; a P-H1-(L1-L2)-H2 alignment of redox centers with an approximately rhombic arrangement of the cytochromec 554 hemes is proposed. The observed reverse phase is ascribed to the post-flash charge redistribution between the hemes. Redox titration of the amplitude of phase C yielded the Em,8.3 values of H1, H2 and L2 hemes: 340±10 mV for H1, 160±20 mV for H2 and −40±40 mV for L2.
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    URL: http://dx.doi.org/10.1007/BF02184153
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    Pigment interactions in chlorosomes of various green bacteria (1994)
    Springer
    Photosynthesis research 41 (1994), S. 175-180 
    Details
    ISSN: 1573-5079
    Keywords: Chlorobium ; Chloroflexus ; chlorophyll ; light-harvesting ; photosynthesis ; resonance Raman
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria.
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    URL: http://dx.doi.org/10.1007/BF02184158
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    The formation and characterization of the in vitro polymeric aggregates of bacteriochlorophyllc homologs fromChlorobium limicola in aqueous suspension in the presence of monogalactosyl diglyceride (1994)
    Springer
    Photosynthesis research 41 (1994), S. 235-243 
    Details
    ISSN: 1573-5079
    Keywords: bacteriochlorophyll ; chlorosomeChlorobium limicola ; green bacteria ; photosynthesis ; monogalactosyl diglyceride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Artificial aggregates of bacteriochlorophyllc (BChlc) were formed in an aqueous medium in the presence of a lipid, monogalactosyl diglyceride (MGDG), and the optical properties of those aggregates were studied by absorption and circular dichroism (CD) mainly. Four BChlc homologs, ([E,E]BChlc F, [P,E]BChlc F, [E,M]BChlc F and [I,E]BChlc F), were isolated from the green photosynthetic bacteriumChlorobium limicola strain 6230. Above 0.0004%, MGDG induced a red-shift of the absorption maxima of BChlc aggregates. At 0.003% MGDG BChlc aggregates showed absorption maxima in the range of 724 to 745 (±3) nm with a shift of 12 to 24 (±3) nm depending on the homolog species. Four kinds of BChlc-MGDG aggregates showed characteristic CD spectra. [E,M]BChlc F gave rise to a CD spectrum similar to that of chlorosomes, while the other three gave spectra of opposite sign. These aggregates are sensitive to 1-hexanol treatment; in a saturating amount (0.85%) of 1-hexanol, all the homologs gave a monomer-like absorption spectrum peaking at 670nm. At an intermediate concentration (0.5%), [E,M]BChlc F showed an enhanced CD intensity, as observed in native chlorosomes. Resonance Raman spectra of the monomer-like BChlc samples indicated that the keto vibrational band at ca. 1640 cm−1 was considerably weakened by the 0.85% 1-hexanol treatment, however the 1680 cm−1 band characteristic of a free keto group did not appear. These results indicate that the artificial aggregates formed by purified BChlc homologs and MGDG are good models for studying chlorosomes structure.
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    Sensitivity of the relative Fpl level of chlorophyll fluorescence induction in leaves to the heat stress (1994)
    Springer
    Photosynthesis research 39 (1994), S. 201-204 
    Details
    ISSN: 1573-5079
    Keywords: automatic determination ; fluorescence parameters ; fluorometer ; induction curve ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The (Fpl-Fo)/Fv value of the fluorescence induction curve is shown to be a more suitable parameter to detect a wider range of heat stress damage to thylakoid membranes as compared to quantities t 1/2 (time of fluorescence rise from Fo to (Fo+Fm)/2 level) and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaacq% aHepaDaaaaaa!39D5!\[\overline \tau \] (the fluorescence induction time defined as the area above the induction curve normalized to Fv=1). A method for exact and automatic Fpl determination is presented. A break point in the quality and behaviour of the fluorescence induction curve of barley leaves incubated at 49°C was reached at the moment (about 240 s) when the transformation of PS II active (QB-reducing) to PS II inactive (QB-non-reducing) centres was completed. The meaning of the standard Fv and Fv/Fm parameter was then changed. The method of Fpl determination described here may help to increase the analytical value of the standard chlorophyll fluorometers.
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    The role of iron in phytoplankton photosynthesis, and the potential for iron-limitation of primary productivity in the sea (1994)
    Springer
    Photosynthesis research 39 (1994), S. 275-301 
    Details
    ISSN: 1573-5079
    Keywords: chlorosis ; diagnostic ; flavodoxin ; iron-limitation ; photosynthesis ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron supply has been suggested to influence phytoplankton biomass, growth rate and species composition, as well as primary productivity in both high and low NO3 − surface waters. Recent investigations in the equatorial Pacific suggest that no single factor regulates primary productivity. Rather, an interplay of bottom-up (i.e., ecophysiological) and top-down (i.e., ecological) factors appear to control species composition and growth rates. One goal of biological oceanography is to isolate the effects of single factors from this multiplicity of interactions, and to identify the factors with a disproportionate impact. Unfortunately, our tools, with several notable exceptions, have been largely inadequate to the task. In particular, the standard technique of nutrient addition bioassays cannot be undertaken without introducing artifacts. These so-called ‘bottle effects’ include reducing turbulence, isolating the enclosed sample from nutrient resupply and grazing, trapping the isolated sample at a fixed position within the water column and thus removing it from vertical movement through a light gradient, and exposing the sample to potentially stimulatory or inhibitory substances on the enclosure walls. The problem faced by all users of enrichment experiments is to separate the effects of controlled nutrient additions from uncontrolled changes in other environmental and ecological factors. To overcome these limitations, oceanographers have sought physiological or molecular indices to diagnose nutrient limitation in natural samples. These indices are often based on reductions in the abundance of photosynthetic and other catalysts, or on changes in the efficiency of these catalysts. Reductions in photosynthetic efficiency often accompany nutrient limitation either because of accumulation of damage, or impairment of the ability to synthesize fully functional macromolecular assemblages. Many catalysts involved in electron transfer and reductive biosyntheses contain iron, and the abundances of most of these catalysts decline under iron-limited conditions. Reductions of ferredoxin or cytochrome f content, nitrate assimilation rates, and dinitrogen fixation rates are amongst the diagnostics that have been used to infer iron limitation in some marine systems. An alternative approach to diagnosing iron-limitation uses molecules whose abundance increases in response to iron-limitation. These include cell surface iron-transport proteins, and the electron transfer protein flavodoxin which replaces the Fe-S protein ferredoxin in many Fe-deficient algae and cyanobacteria.
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    Molecular topology of the Photosystem II chlorophyll a binding protein, CP 43: Topology of a thylakoid membrane protein (1994)
    Springer
    Photosynthesis research 40 (1994), S. 11-19 
    Details
    ISSN: 1573-5079
    Keywords: photosynthesis ; membrane protein ; protein structure ; light harvesting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used antibodies generated against synthetic peptides to determine the topology of the 43 kD chlorophyll a binding protein (CP 43) of Photosystem II. Based on the pattern of proteolytic fragments detected (on western blots) by peptide specific antibodies, a six transmembrane span topological model, with the amino and carboxyl termini located on the stromal membrane surface, is predicted. This structure is similar to that predicted for CP 47, a PS II chlorophyll a binding protein (Bricker T (1990) Photosynth Res 24: 1–13). The model is discussed in reference to the possible location of chlorophyll binding sites.
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    The Wageningen Rhizolab — a facility to study soil-root-shoot-atmosphere interactions in crops (1994)
    Springer
    Plant and soil 161 (1994), S. 275-287 
    Details
    ISSN: 1573-5036
    Keywords: crop growth ; gas exchange ; minirhizotrons ; nutrients ; photosynthesis ; respiration ; rhizotron ; root observation ; root growth ; water balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A research facility is described for the integrated study of soil-root-shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight below-ground compartments aligned along a corridor. A rain shelter automatically covers the experimental area at the start of rainfall. Compartments are 125 cm × 125 cm and 200 cm deep. Each compartment has a separate drip irrigation system. Crop canopy photosynthesis, respiration, and transpiration can be measured simultaneously and continuously on four out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth. Multiple sensors for measuring soil moisture status, electrical conductivity, temperature, soil respiration, trace gases and oxygen are installed in spatial patterns in accordance with the requirements of the experiments. Sensors are connected to control and data-acquisition devices. Likewise, provisions have been made to sample manually the soil solution and soil atmosphere. Root observation tubes (minirhizotrons) are installed horizontally at depth intervals ranging from 5 cm (upper soil layers) to 25 cm (below 1 m). The facility is at present in use to study growth and development of vegetation (crops) in relation to drought, nutrient status, soil-borne diseases, and underground root competition. One important application is the study of elevated CO2 concentration and climate change and the way they affect crops and their carbon economy. Growth and development of field grown vegetables and winter cover crops are also evaluated. The common aspect of those studies is to gain a better understanding of crop growth under varying environmental conditions, and to collect datasets that may help to improve mechanistic crop growth simulation models that can address suboptimal growth conditions.
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    URL: http://dx.doi.org/10.1007/BF00046399
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    Root movements: Towards an understanding through attempts to model the processes involved (1994)
    Springer
    Plant and soil 165 (1994), S. 293-300 
    Details
    ISSN: 1573-5036
    Keywords: gravitropism ; living systems theory ; nutation ; Phleum pratense L. ; simulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Roots have the ability to change the direction of their forward growth. Sometimes these directional changes are rapid, as in mutations, or they are slower, as in tropisms. The gravitational force is always present and roots have an efficient graviperception mechanism which enables them to initiate gravitropic movements. In trying to model and simulate the course of gravitropic root movements with a view to analyse the component processes, the following aspects of the plant's interaction with gravity have been considered: (1) The level of organization (organism, organ, cell) at which the movement process is expressed; (2) whether the gravity stimulation event is dynamic or static (i.e. whether or not physiologically significant displacements take place with respect to the gravity vector); (3) the sub-systems involved in movement and the processes which they regulate; (4) the mathematical characterization of the relevant sub-systems. A further allied topic is the nature of nutational movements and whether they are linked with gravitropic movements in some way. In considering how they can best be modelled, two types of nutational movements are proponed: stochastic nutation and circumnutation. Most, if not all, natural movements developed in response to static gravistimulation can be viewed as gravimorphisms. This applies at the levels of cell, organ and organism. However, when a system at any one of these levels experiences dynamic gravistimulation, because of its inherent homeostatic properties, it is induced to regenerate a state similar to that previously held. Thus, gravitropism is a regenerative gravimorphic process at the level of the organ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008072
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  • 94
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    Root growth and nitrate utilization of maize cultivars under field conditions (1994)
    Springer
    Plant and soil 163 (1994), S. 267-277 
    Details
    ISSN: 1573-5036
    Keywords: cultivar ; critical root length density ; field experiment ; nitrate ; N utilization ; root growth ; uptake rate ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a 2-year field study conducted on a high fertilized Gleyic Luvisol in Stuttgart-Hohenheim significant differences among 10 maize cultivars were observed in soil nitrate depletion. The different capability of the cultivars to utilize nitrate particularly from the subsoil was positively correlated with (a) shoot N uptake at maturity, and (b) root length density (Lv) in the subsoil layers at silking. “Critical root length densities” for nitrate uptake were estimated by (a) calculating uptake rates per unit root length (U), (b) subsequent calculation of needed nitrate concentration in soil solution (C1) to sustain calculated U according to the Baldwin formula, and (c) reducing measured Lv and proportionate increase of U until needed concentration equaled measured concentration. Uptake rate generally increased with soil depth. “Critical root length densities” for cultivar Brummi (high measured root length densities and soil nitrate depletion) at 60–90 cm depth ranged from 7 % (generative growth) to 28 % (vegetative growth) of measured Lv Measured root length density of each other cultivar was higher than “critical root length density” for Brummi indicating that the root system of each cultivar examined would have been able to ensure N uptake of Brummi. Positive relationships between root length density and nitrate utilization as indicated by correlation analysis therefore could not be explained by model calculations. This might be due to simplifying assumptions made in the model, which are in contrast to non-ideal uptake conditions in the field, namely irregular distribution of roots and nitrate in the soil, limited root/soil contact, and differences between root zones in uptake activity. It is concluded from the field experiment that growing of cultivars selected for high N uptake-capacity of the shoots combined with “high” root length densities in the subsoil may improve the utilization of a high soil nitrate supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007976
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  • 95
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    Ultrastructural responses of root caps to the herbicides chlorsulfuron and metsulfuron methyl (1994)
    Springer
    Plant and soil 167 (1994), S. 127-134 
    Details
    ISSN: 1573-5036
    Keywords: herbicides ; chlorsulfuron ; metsulfuron methyl ; root cap ultrastructure ; root growth ; Pisum sativum ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Herbicide residues may affect seedlings during early stages of their development. We studied this possibility by the use of light and electron microscopy after incubation of germinating seeds ofPisum sativum L. andZea mays L. with different concentrations of chlorsulfuron and metsulfuron-methyl. By in vitro experiments, we have shown that both herbicides caused growth reduction of the very young roots, and severe ultrastructural alterations and injuries of the root caps of both species. Chlorsulfuron caused increase of electron-dense material in the vacuoles, cytoplasmic degeneration even in the inner secretory cell layers of the cap, and disruption of the amyloplast envelopes with release of the statolithic starch grains. In the initial cell complex of the root cap, the herbicides caused the formation of large concentric aggregates of the rough ER and wall disformations in the cells adjacent to this complex. Scanning electron microscopic observations revealed a decrease of the slime layer ensheathing the root cap and the subapical root surface. We conclude that even in early stages of seed germination, both herbicides seriously affect the gravity perception centre (consisting of the statocytes), and the secretory tissue of the root caps, thus probably disturbing the processes of gravitropism and the protective slime secretion of the roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01587607
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  • 96
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    Effects of nitrogen supply on the acclimation of photosynthesis to elevated CO2 (1994)
    Springer
    Photosynthesis research 39 (1994), S. 389-400 
    Details
    ISSN: 1573-5079
    Keywords: elevated CO2 ; nitrogen supply ; photosynthesis ; acclimation ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A common observation in plants grown in elevated CO2 concentration is that the rate of photosynthesis is lower than expected from the dependence of photosynthesis upon CO2 concentration in single leaves of plants grown at present CO2 concentration. Furthermore, it has been suggested that this apparent down regulation of photosynthesis may be larger in leaves of plants at low nitrogen supply than at higher nitrogen supply. However, the available data are rather limited and contradictory. In this paper, particular attention is drawn to the way in which whole plant growth response to N supply constitutes a variable sink strength for carbohydrate usage and how this may affect photosynthesis. The need for further studies of the acclimation of photosynthesis at elevated CO2 in leaves of plants whose N supply has resulted in well-defined growth rate and sink activity is emphasised, and brief consideration is made of how this might be achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014593
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  • 97
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    The influence of ammonia on the growth and photosynthesis of Ruppia drepanensis Tineo from Doñana National Park (SW Spain) (1994)
    Springer
    Hydrobiologia 275-276 (1994), S. 219-231 
    Details
    ISSN: 1573-5117
    Keywords: Ruppia drepanensis ; ammonia toxicity ; temperature effects ; photosynthesis ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a laboratory experiment, Ruppia drepanensis Tineo seedlings from a brackish marsh in Southern Spain were grown at 20 and 30 °C, at three different nitrogen levels. These levels were obtained by the addition of a slow release fertilizer (23% NH4NO3 by weight) to a sediment mixture of sand and clay (3:1). Several morphometric parameters were recorded during the first five weeks of the experiment, and photosynthesis and respiration were measured after 7 weeks of growth. Results showed a significant reduction of growth and development with increasing nitrogen and temperature levels. Dark respiration increased strongly at high nitrogen levels. At the same time, net photosynthesis at 250 and 500 µE m-2 s-1, Pm, Km and LCP were not affected by either factor. We attribute these phenomena to ammonia toxicity, since relatively high total ammonia (NH3 + NHf4 p+) levels were found in the interstitial water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026713
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  • 98
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    Environmental control of phytoplankton productivity in turbulent turbid systems (1994)
    Springer
    Hydrobiologia 289 (1994), S. 65-72 
    Details
    ISSN: 1573-5117
    Keywords: photosynthesis ; selective environments ; resuspension ; disturbance ; rivers ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factors affecting phytoplankton productivity are analysed in turbid systems, such as shallow lakes and rivers. When resuspension from the sediment or loading from the catchment significantly increases inorganic (non-algal) turbidity and hence light attenuation potentials for high production are not realised. Energy available for phytoplankton growth is strongly regulated by underwater light availability which depends on the critical mixing depth, fluctuating light intensities and algal circulation patterns. Higher production rates in shallow waters are often compensated by greater algal respiration due to higher water temperatures when compared to deeper lakes. Total daily integral production of turbulent, turbid environments can be predicted from a combination of easily measured variables such as maximum photosynthetic rates, algal biomass, surface irradiance and some measure of underwater light attenuation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007409
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  • 99
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    Light differentially regulates lateral and longitudinal auxin transport in the mesocotyl of etiolated maize seedlings (1994)
    Springer
    Plant growth regulation 14 (1994), S. 167-171 
    Details
    ISSN: 1573-5087
    Keywords: auxin-transport ; indoleacetic acid ; maize ; photoinhibition ; transport ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The uptake of IAA into excised mesocotyls of non-irradiated maize seedlings was linear up to a concentration of about 4×M and in this range there was a tight coupling between the IAA in the stele and the cortex. Prior irradiation with white light of intact seedlings unbalanced this coupling. Lateral and longitudinal transport were affected differently. In the stele, the effect of prior irradiation on longitudinal transport was multiphasic, with an initial stimulatory effect followed by a negative effect at longer prior irradiation times. The lateral transport from the stele to the cortex showed no stimulatory effect and appeared to be inhibited within at least 15 min. The effect of the prior irradiation on longitudinal transport in the stele appeared to be a high intensity effect. In contrast, the effect of the prior irradiation on the lateral transport from the stele to the cortex was saturated at much lower intensities. The data suggest that the light induced change in the lateral transport of IAA between the two tissues may be due to changes either in the number of open lateral transport channels/carriers or in the conductivity of these channels/carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025219
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  • 100
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    Effects of homobrassinolide application on plant metabolism and grain yield under irrigated and moisture-stress conditions of two wheat varieties (1994)
    Springer
    Plant growth regulation 14 (1994), S. 173-181 
    Details
    ISSN: 1573-5087
    Keywords: homobrassinolide ; irrigated ; membrane stability ; moisture-stress ; nitrate reductase activity ; photosynthesis ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Homobrassinolide (BR) was applied either as a seed treatment or foliar spray to two contrasting wheat varieties, viz. C306 (drought tolerant) and HD2329 (drought susceptible), to examine its effects on plant metabolism and grain yield under irrigated and moisture-stress/rainfed conditions. BR application resulted in increased relative water content, nitrate reductase activity, chlorophyll content and photosynthesis under both conditions. BR application also improved membrane stability (lower injury). These beneficial effects resulted in higher leaf area, biomass production, grain yield and yield related parameters in the treated plants. All the treatments were significantly better than the untreated control. Generally, 0.05 ppm either as a seed treatment or foliar spray was more effective than the 0.01 ppm treatment. The drought-tolerant genotype C306 showed more response to BR application under moisture-stress/rainfed condition than HD 2329. Increased water uptake, membrane stability and higher carbon dioxide and nitrogen assimilation rates under stress seemed to be related to homobrassinolide-induced drought tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025220
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