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  • Angiosperms  (62)
  • Saccharomyces cerevisiae  (34)
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  • 1986  (96)
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  • 1985-1989  (96)
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  • 1
    Electronic Resource
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    Springer
    Current genetics 10 (1986), S. 943-945 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; α-factor ; Protoplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When Mat a cells are treated with α-factor prior to being protoplasted and fused, the frequency of karyogamy is higher than in unarrested controls.
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  • 2
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    Current genetics 10 (1986), S. 665-670 
    ISSN: 1432-0983
    Keywords: Multiple drug resistance ; Genetic mapping ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the yeast Saccharomyces cerevisiae, two nuclear pleiotropic drug resistance mutations pdr3-1 (former designation muc PR) and pdr3-2 (former designation DRI9/T7) have been selected as resistant to mucidin and as resistant to chloramphenicol plus cycloheximide, respectively. The pdr3 mutations were found not to affect the plasma membrane ATPase activity measured in a crude membrane fraction. Meiotic mapping using strains with standard genetic markers revealed that mutation pdr3-1 is centromere linked on the left arm of chromosome II at a distance of 5.9 ± 3.3 cM from its centromere and 11.6 ± 3.1 cM from the marker pet9. The centromere linked pdr3-2 mutation exhibited also genetic linkage to pet9 with a map distance of 9.8 ± 3.2 cM. These results indicate that pdr3-1 and pdr3-2 are alleles of the same pleiotropic drug resistance locus PDR3 which is involved in the control of the plasma membrane permeability in yeast.
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  • 3
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    Current genetics 10 (1986), S. 657-664 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Amino acid biosynthesis ; General control ; GCD-genes ; GCN-genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutant strains, resistant against the amino acid analogues 5-methyltryptophan, 5-fluorotryptophan and canavanine were isolated, starting with a trp2 leaky auxotrophic strain. Of 10 such strains, only four turned out to be of the “general control derepressed” (gcd) mutant type. Three other isolates were shown to be defective in the general amino acid permease system, while the remaining three strains displayed low spore viability and were not further investigated. Complementation tests amongst the four new gcd-mutant strains, including strain RH558 gcd2-1 isolated earlier, yielded five complementation groups: GCD2, GCD3, GCD4, GCD5, and GCD6. All mutant strains showed a dual phenotype, which was not separable by wild type backcrosses: “constitutive derepression” and “slow growth”. Epistatis of all gcd mutations over gcn1-1, gcn2-1 and gcn3-1 was found with respect to both phenotypes, except for gcd5-1, which was lethal in these combinations. On the other hand gcn4-101 was found to be epistatic over all gcd mutations, but only with respect to the “constitutive derepression” phenotype, and not to “slow growth”; again the combination with gcd5-1 was lethal. Mutation gcd2-1 was mapped on chromosome VII, 50 cM from leu1 and 22 cM from ade6. A new model is discussed, in which GCD-genes are involved in the amino acid uptake into the vacuoles.
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  • 4
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    Current genetics 10 (1986), S. 491-494 
    ISSN: 1432-0983
    Keywords: Protoplast fusion ; Saccharomyces cerevisiae ; Schwanniomyces castellii ; Starch fermentability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prototrophic hybrids have been obtained by the fusion of various auxotrophic haploid strains of Saccharomyces cerepisiae and Schwanniomyces castellii. The fusion hybrids showed starch fermentability which derived from one of the fusion parents, S. castellii. Surprisingly, these fusion hybrids were found to exhibit excellent sporulation and spore germination. The progenies of these fusion hybrids showed a few aberrant segregations, but mostly normal segregation for auxotrophic genetic markers. They also showed many tetrads with an apparently digenic segregation (2:2, 3:1 and 4:0) for starch fermentation. On the other hand, mating types of segregants of the fusion hybrids were determined by the prototrophic recovery method. Consequently, tetrad types for mating type were mostly 2a:1α:1 non-mater and several asci showed tetrad types of 2a:2 non-mater and 2a:2α. The 60 prototrophic fusion hybrids and its segregants did not secrete α-amylase on the starch agar plate. However, all of the data suggested that fusion hybrid could carry two dominant genes (STAB and STAC) to ferment starch, and that the two genes STAB and STA2 may be identical or allelic as may be the genes STAC and STA3.
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  • 5
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    Current genetics 11 (1986), S. 93-96 
    ISSN: 1432-0983
    Keywords: Uracil permease gene ; Saccharomyces cerevisiae ; Chromosomal mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gene FUR4, coding for the uracil permease in Saccharomyces cerevisiae, was mapped on chromosome II, at a distance of 7.8 cM from the centromere on the right arm of the chromosome. In a first step, we used the chromosome loss mapping method developed by Falco and Botstein (1983) to determine on which chromosome the gene mapped. After the observation that FUR4 was closely linked to GAL10, one of the three genes forming the gal cluster (Bassel and Mortimer 1971), we could determine precisely the position of the gene on chromosome II.
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  • 6
    ISSN: 1432-0983
    Keywords: Schizosaccharomyces pombe ; Saccharomyces cerevisiae ; DNA ligase ; DNA damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary UV-irradiation of stationary phase cells of Saccharomyces cerevisiae and Schizosaccharomyces pombe leads to a 9-fold and 90-fold increase in transcript levels from the respective DNA ligase genes CDC9 and CDC17, whereas exponential cells show only 3-fold and 2-fold increases. Induction of CDC9 after MMS treatment and γ-irradiation was also observed by using a CDC9-lacZ translational fusion and assaying for β-galactosidase. Surprisingly, irradiation of S. cerevisiae induces only a 50% increase in DNA ligase itself, probably reflecting the extremely high in vivo stability of the enzyme. The UV-induction of ligase may be part of a “fail-safe” mechanism which, together with the enzyme stability, ensures adequate supplies of this essential enzyme.
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  • 7
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    Current genetics 11 (1986), S. 193-200 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Ty elements ; Transposable elements ; Retroviruses ; tRNA genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have isolated and characterized a Ty element from a yeast cosmid library which exhibits several unsual features: it is flanked by non-homologous delta elements and directly associated with a singular delta element. A tRNA(Glu3) gene and tRNA(Cys) gene are found in conjunction with this element, located in opposite orientation on either end of it. The sequence information now available for several Ty elements has been used in a detailed comparative analysis to determine conserved features among the Ty elements, preferably between class I elements and a class II element. Highly conserved sequence motifs appear to be located at the borders of particular segments that correspond to the putative protein domains of the Tys. Furthermore, we include a comparison of the best-conserved amino acid homologies for these putative proteins of Ty elements, transposable elements from other organisms and several retroviral proviruses to confirm their close structural resemblance.
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  • 8
    ISSN: 1432-0983
    Keywords: Rho°-petites ; Lycorine ; Mitochondrial DNA replication ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper describes the isolation and characterization of mutants affected in the maintenance of the mitochondrial (mt) genome. The rationale of the screening procedure is based on the observation that the alkaloid lycorine inhibits growth of rho −-mutants, whereas rho°-mutants, devoid of mt DNA, are resistant to this drug (Del Giudice et al. 1984). Fourteen temperature sensitive mutants have been isolated that display the following phenotype: -Growth on fermentable medium at 23°C and 35°C (exclusion of general temperature-sensitive mutants). -no growth at 23°C and growth at 35°C on fermentable medium containing lycorine (selection for mutants producing rho°-petites). -growth at 23°C and no growth an 35°C on non-fermentable medium (selection for temperature-dependent loss of respiratory competence). These mutants were termed tmm (for temperature sensitive maintenance of mt genome). Mutant tmm1-1 was analyzed genetically and biochemically. It carries a recessive nuclear mutation which gives rise to 90–95% cytoplasmic petites at the non-permissive temperature. The population of petites consists of more than 95% rho°-petites as shown by their resistance to lycorine, by staining with 4′,6-diamidino-2-phenylindole (DAPI), and by Southern hybridization with mt DNA probes. Wild-type control cultures produced approximately 1% petites with less than 10% rho°-mutants.
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  • 9
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    Current genetics 11 (1986), S. 211-215 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Hyperresistance ; DNA damaging agents ; Genotoxic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to study resistance to DNA damaging agents, yeast DNA segments conferring hyperresistance in this organism to such genotoxic agents were selected for among yeast cells transformed by a yeast genome library based on the multi-copy vector plasmid YEp13. Genetic variants hyperresistant to 4-nitroquinohne-N-oxide, formaldehyde, and alkylating agents were isolated and the respective hyperresistance determinants shown to co-segregate with the vector plasmid. Phenotypical characterization indicated different degrees of resistance, few cases of cross-resistance and differing structural stability of the cloned DNA. By transfer to E. coli and subsequent retransformation of yeast a number of plasmids was shown to stably carry the genetic information for hyperresistance.
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  • 10
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    Current genetics 11 (1986), S. 217-225 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Gene cloning ; Invertase genes ; Multicopy vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Six unlinked loci for invertase structural genes are known in the yeast Saccharomyces cerevisiae: SUC1-SUC5 and SUC7. These genes are similar in structure and expression but not identical. Different yeast strains possess none, one or several of these genes. We have isolated the genes SUC1-SUC5, subcloned them into the multicopy vector YEp24 and compared the expression of the five SUC genes in one recipient strain. SUC2 was isolated by transformation of a suc0 strain with a gene pool and complementation to sucrose fermentation. SUC4 was cloned from a minipool of chromosomal fragments which were shown to contain SUC4 by Southern hybridization. SUC1, SUC3 and SUC5 were isolated using the method of plasmid eviction. A plasmid containing regions flanking SUC4 was integrated next to these SUC genes. The plasmid together with the SUC genes were then cut out of the chromosome using an appropriate restriction endonuclease. The length of chromosomal DNA fragments containing the different SUC genes were 4.8 kb for SUC1, 5.2 kb for SUC2, 4.8 kb for SUC3, 12.8 kb for SUC4 and 17.2 kb for SUC5. Fragments containing the complete SUC genes and the sequences controlling their expression were subcloned into YEp24 and transformed into a strain without any active invertase gene. Invertase activity of transformants was measured after growth repressing (8% glucose) and derepressing (2% raffinose) conditions. As expected from results with strains carrying the individual SUC genes in a chromosomal location, the SUC genes were expressed to a different extent.
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  • 11
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Nucleo-mitochondrial interactions ; Mitochondrial status ; Dominant lycorine resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutants resistant to 200 µg/ml of the alkaloid lycorine (LYC R) in non-fermentable substrate were isolated after nitrosoguanidine mutagenesis. Tetrad analysis and growth of heterozygous (LYC R/lyc s) diploids from two different mutants revealed that a single nuclear and dominant mutation is responsible for the resistant phenotype. In the wild type total protein synthesis is only slightly inhibited, whereas DNA and RNA synthesis is lowered to about 30% of the control. In the lycorine resistant mutants all macromolecular syntheses are unaffected by the drug.
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  • 12
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Cytochrome c ; Regulatory gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The CYP1 gene has previously been identified as coding for a positive trans active factor that activates the expression of CYC1 and CYP3, which are the structural genes for isol- and iso2-cytochrome c. Two phenotypically distinct classes of CYP1 mutations can be obtained indicating that CYC1 and CYP3 are differentially regulated by the product of CYP1. The HAP1 gene codes for a product which has previously been proved to be necessary for the expression of the heme dependent CYC1-UAS1 cis regulatory sequence. In this article, we show by complementation and recombination that CYP1 and HAP1 are the same gene, moreover we identify hap1-1 as an iso2-cytochrome c underproducer mutation of the CYP1 gene.
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  • 13
    ISSN: 1432-0983
    Keywords: agα1 Mutant ; Agglutination ; Gene dose effect ; Mapping ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A recessive agα1 mutation leads to specific defect in sexual agglutinability specifically in α cells of the yeast Saccharomyces cerevisiae. The cryptopleurine resistance gene cryR 1, closely linked to the mating type locus, was used to select α/α strains which emerged from α/α strains by mitotic nonreciprocal recombination, to genetically analyse agα1, since agα1 is expressed only in α mating type. The agα1 gene was found to be linked to the centromere tightly, to met3 at 4.4 cM, and to ilv3 at 12 cM on chromosome X. Sexual agglutinability of α cells was shown to be dependent on the dose of the AGα1 gene, using α/α isogenic strains carrying AGα1/AGα1, AGα1/agα1 or agα1/agα1. The sst2-1 mutation did not suppress the agα1 mutation. Based on these results, function of the AGα1 gene is discussed.
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  • 14
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    Archives of microbiology 145 (1986), S. 27-31 
    ISSN: 1432-072X
    Keywords: Nitrite ; Sulfite ; Saccharomyces cerevisiae ; ATP ; Energy metabolism ; Inorganic phosphate ; Glyceraldehyde-3-phosphate dehydrogenase ; Glucose-6-phosphate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After addition of 5 mM sulfite or nitrite to glucose-metabolizing cells of Saccharomyces cerevisiae a rapid decrease of the ATP content and an inversely proportional increase in the level of inorganic phosphate was observed. The concentration of ADP shows only small and transient changes. Cells of the yeast mutant pet 936, lacking mitochondrial F1ATPase, after addition of 5 mM sulfite or nitrite exhibit changes in ATP, ADP and inorganic phosphate very similar to those observed in wild type cells. They key enzyme of glucose degradation, glyceraldehyde-3-phosphate dehydrogenase was previously shown to be the most sulfiteor nitrite-sensitive enzyme of the glycolytic pathway. This enzyme shows the same sensitivity to sulfite or nitrite in cells of the mutant pet 936 as in wild type cells. It is concluded that the effects of sulfite or nitrite on ATP, ADP and inorganic phosphate are the result of inhibition of glyceraldehyde-3-phosphate dehydrogenase and not of inhibition of phosphorylation processes in the mitochondria. Levels of GTP, UTP and CTP show parallel changes to ATP. This is explained by the presence of very active nucleoside monophosphate kinases which cause a rapid exchange between the nucleoside phosphates. The effects of the sudden inhibition of glucose degradation by sulfite or nitrite on levels of ATP, ADP and inorganic phosphate are discussed in terms of the theory of Lynen (1942) on compensating phosphorylation and dephosphorylation in steady state glucose metabolizing yeast.
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  • 15
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    Archives of microbiology 145 (1986), S. 104-106 
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; α Factor ; Trifluoperazine ; Chlorpromazine ; Calmodulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Saccharomyces cerevisiae α factor pheromone arrest growth of cells of the a mating type (MAT a) at the G1 phase of the cell cycle. When treatment of MAT a cells with α factor was carried out in the presence of anticalmodulin drugs, trifluoperazine or chlorpromazine, the extent of cell growth arrest induced by α factor was reduced or even became undetectable. These results lend support to the hypothesis that calmodulin plays a role as mediator in the action of α factor on MAT a cells.
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  • 16
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    Archives of microbiology 146 (1986), S. 214-220 
    ISSN: 1432-072X
    Keywords: Yeasts ; Cell wall ; Mannoproteins ; Aculeacin A ; Glucan ; Protoplasts ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inhibition of the synthesis of alkali-insoluble glucan by aculeacin A in Saccharomyces cerevisiae cells caused a decrease in the incorporation of a high molecular weight heterogeneous mannoprotein material and of a 33000 mannoprotein into the wall network. This was concomitant with the excretion of the latter molecule into the growth medium. Regenerating yeast protoplasts liberated considerable amounts of the heterogeneous material to the medium independently of the presence of aculeacin. The protoplast walls did lack this component and contained only minor amounts of the 33000 molecule, which was also completely absent from walls of aculeacin-treated protoplasts. Considerable levels of the 33000 species were immunodetected in the supernatants from treated and untreated protoplasts. These results point to the existence of specific interactions between the glucan network of the yeast cell surface and some of the wall mannoproteins. On the other hand, the presence of a population of SDS-solubilizable mannoproteins in the wall was independent of glucan levels.
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  • 17
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    Archives of microbiology 146 (1986), S. 221-226 
    ISSN: 1432-072X
    Keywords: Exoglucanase ; Saccharomyces cerevisiae ; Secretory mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum (sec 18), from the Golgi body (sec 7) and in transport of secretory vesicles (sec 1), accumulated exoglucanase, a constitutive yeast activity, when incubated at the restrictive temperature (37°C). Different proportions of the accumulated activity were released by mutant cells under permissive conditions. The presence or absence of cycloheximide during the secretion period made no differences in the results. More than 90% of the internal activity was bound to membrane in wild type cells. However, only the soluble pool underwent changes during the accumulation or secretion periods. The bulk of secretory invertase accumulated by sec 1 was also soluble. By contrast sec 7 and sec 18 accumulated membrane-bound as well as soluble invertase forms and both were secreted in similar proportions in each mutant. More than 90% of the accumulated invertase was secreted at the permissive temperature in sec 18 cells. That percentage was significantly lower for exoglucanase (〈65%). Concomitantly, invertase accumulated by this mutant exited from the cells with a lower half time (t 1/2=150 min). These results may be interpreted assuming that exoglucanase is exported by a passive flow of the soluble pool.
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  • 18
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    Archives of microbiology 145 (1986), S. 32-38 
    ISSN: 1432-072X
    Keywords: Sulphate assimilation ; Adenylylsulphate 3′-phosphotransferase EC 2.7.1.25 ; Escherichia coli ; Saccharomyces cerevisiae ; Enzyme purification ; Enzyme regulation ; Thiredoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adenylylsulphate kinase (EC 2.7.1.25, ATP:adenylylsulphate 3′-phosphotransferase) has been isolated from Escherichia coli and from Saccharomyces cerevisiae. As major steps of purification, affinity chromatography on Sepharose CL 6B (“blue” or “red”) and chromatofocusing on polybuffer PBE 94tm were employed. The proteins were obtained in nearly homogeneous state after five chromatographic steps. The isolated enzymes from both sources appeared predominantly to exist as dimers. Upon reduction of the protein with dithiothreitol, it desintegrated into assumingly identical smaller subunits (E. coli rom Mr 90-85000 to 45-40000 and s. cerevisiae from 52-49500 to 28-29500). Both forms, dimer and monomer were found catalytically active. Preincubation of the isolated enzyme from either source in the presence of thioredoxin plus DTT, reduced glutathione or DTT increased the activity significantly. Treatment of the enzyme with SH-blocking reagents inactivated the enzyme irreversibly as compared to the inactivation caused by oxidants (2,6-dichlorophenol-indophenol, ferricyanide or oxydized glutathione). This oxidant induced inactivation was less pronounced for the fungal enzyme than for the bacterial protein. The enzyme from E. coli required thioredoxin in order to alleviate the GSSG-induced inactivation.
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  • 19
    ISSN: 1432-072X
    Keywords: Bacillus megaterium ; Saccharomyces cerevisiae ; Ethionine ; Protein degradation ; Abnormal protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Degradation of abnormal proteins in Bacillus megaterium and Saccharomyces cerevisiae in vivo was compared with that in cell-free extracts. Protein degradation in vivo, when the cells were labelled with 14C-leucine during growth in the presence of ethionine, was affected by the concentration of the analogue used. Proteins synthesized in the presence of 0.2–1 mM ethionine were degraded most rapidly in both organisms. The proteolytic enzyme system of yeast degraded the analogue-containing proteins in vitro faster than the normal proteins. This holds also for proteins synthesized in the presence of 5 mM ethionine, whose degradation in vivo was impaired. The proteolytic system of B. megaterium, on the other hand, was unable in vitro to differentiate between normal and abnormal proteins. Denatured proteins underwent preferential degradation over normal and ethionine-containing proteins.
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  • 20
    ISSN: 1573-4935
    Keywords: Candida utilis ; cellulase ; DNAse ; β-glucuronidase ; Hansenula jadinii ; protoplast ; Saccharomyces cerevisiae ; Schizosaccharomyces pombe ; spheroplast ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Efficient preparation of spheroplasts fromCandida utilis, Saccharomyces cerevisiae, andSchizosaccharomyces pombe, using a purified mixture of enzymes fromTrichoderma harzianum, is described. Limitations of other methods, and differences between yeasts are demonstrated.
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  • 21
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    Molecular genetics and genomics 203 (1986), S. 73-78 
    ISSN: 1617-4623
    Keywords: Catalase T ; CTT1 ; Saccharomyces cerevisiae ; Yeast ; Heme control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 5′-flanking region of the Saccharomyces cerevisiae catalase T gene (CTT1) and the part of the gene coding for the N-terminus of catalase T were sequenced. 5′-Ends of transcripts of the region were located by S1 nuclease mapping and primer extension. To analyse control elements in the upstream region, a CTT1-lacZ gene fusion was constructed. Deletion analysis was carried out within a part of the 5′-flanking region showing homology to the upstream region of the yeast CYC1 gene. Like the CTT1 gene, this gene is controlled by heme, oxygen and glucose. The results obtained show that the CTT1 gene is positively controlled by heme. Tentative evidence has been obtained for the involvement of upstream sequences homologous to USA1 and USA2 of the CYC1 gene in heme control. Further, a negative site has been located between the upstream activator sites and the transcription start. Within this negative region a ten base-pair sequence was detected that shows high homology to a sequence located within a negative control region of the CYC1 gene and some homology to the negative control elements of the S. cerevisiae CAR1 and CAR2 genes.
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  • 22
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Gene expression ; Cell cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have examined the pattern of transcription exhibited by four genes in the dTTP biosynthetic pathway of Saccharomyces cerevisiae. Consistent with the results reported previously by Storms et al. (1984), the TMP1 (or CDC21) gene encoding thymidylate synthase was found to be transcribed in a periodic manner during the cell cycle with maximal mRNA levels occurring just prior to the onset of DNA replication. Three other genes in this pathway DCD1, DUT1 and DFR1 encoding dCMP deaminase, dUTP pyrophosphatase and dihydrofolate reductase, respecitively, exhibited relatively constant levels of transcription throughout the cell cycle. These results, particularly for DFR1, are in marked contrast with those obtained in other eukaryotic systems which have suggested that, in general, genes encoding enzymes involved in DNA precursor synthesis are subject to cell cycle regulation. Thus, periodic transcription is not a property common to all genes involved in DNA replication in this eukaryote.
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  • 23
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    Molecular genetics and genomics 205 (1986), S. 422-427 
    ISSN: 1617-4623
    Keywords: SUC2 gene ; Active chromatin ; DNase I hypersensitive sites ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The DNase I sensitivity of chromatin of the yeast SUC2 gene, which encodes two forms of invertase, has been studied both in the genome and in a multicopy plasmid carrying the gene and its flanking sequences. Whereas little if any difference in the DNase I sensitivity of the flanking regions was found between the repressed and the derepressed states, derepression of the gene was accompanied by a large increase in the sensitivity of the transcribed region. A well-defined DNase I hypersensitive site was found centered at ∼ 120 bp downstream from the end of the coding region. This site seems to be flanked in the 3′ non-coding region by strictly positioned nucleosomes, and the structure of this region changes upon derepression. In the 5′ non-conding region two DNase I hypersensitive sites have been found flanking the TATA box and a set of three closely spaced hypersensitive sites occurs in an upstream regulatory sequence. The structure of these latter sites depends on the on-off state of transcription.
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  • 24
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; ARO3 gene ; DAHP synthase ; Regulation ; Gene cloning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Regulation of the two isozymes of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHP synthase; EC 4.1.2.15) encoded by the genes ARO3 and ARO4 of Saccharomyces cerevisiae was studied. Both genes were shown to respond equally well to the general control of amino acid biosynthesis. Strains with mutations in these two genes were obtained by selecting first for a single aro3 mutation and afterwards for a double aro3 aro4 mutation. Gene ARO3, coding for the phenylanine-dependent isozyme of DAHP synthase was cloned on the 2 μm multicopy vector pJDB207 by complementation of mutation aro3-1 in yeast. The ARO3 gene, carried originally on a 9.6 kb BamHI fragment (plasmid pME541A), was subcloned on a 1.9 kb HindIII-XbaI fragment (plasmid pME543). A transcript of about 1.5 kb was shown to proceed from the HindIII towards the XbaI site. Expression from the 9.6 kb as well as from the 1.9 kb fragment was normal on a multicopy vector, since in both cases DAHP synthase levels of about 50-fold the wild-type level were observed.
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  • 25
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Arginase ; Regulation of gene expression
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary We localized the chromosomal targets of several of the regulatory controls of expression of theCAR1 gene. Fusion tolacZ of several fragments of the 5′ non-coding region showed that induction ofCAR1 by arginine is positively regulated by the products of theARGR genes. The target lies upstream of another site where repression by the CARGRI molecule occurs. The latter control is not specific to arginine catabolism since it also affectsCYC-1 and indeed does not appear to involve arginine. The primary target of the two other regulatory allelesCARGRII andCARGRIII is not situated in the 5′ non-coding region. Deletion analysis supports the fusion data and confirms the order of the regulatory regions: 5′—nitrogen catabolite repression—activation by arginine—CARGRI-mediated repression—CAR1.
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    Molecular genetics and genomics 202 (1986), S. 42-47 
    ISSN: 1617-4623
    Keywords: Minicells ; Histidinol phosphatase ; Recombinant plasmids ; Salmonella typhimurium ; Saccharomyces cerevisiae
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    Notes: Summary The bifunctional enzyme imidazoleglycerolphosphate dehydratase and histidinolphosphate phosphatase is encoded by the hisB gene. The fourth gene of the histidine operon, hisB, was cloned and mapped on a 2,300 base pair DNA fragment. In the present study we report the complete nucleotide sequence of the hisB gene of Escherichia coli. The gene is 1,068 nucleotides long and codes for a protein of 355 amino acids with an apparent molecular weight of 39,998 daltons. The protein product(s) of the hisB region of both Salmonella typhimurium and E. coli were identified by subcloning and expression in an in vitro translation system. In both organisms the hisB gene directed the synthesis of a single protein with an apparent molecular weight of 40,500 daltons, consistent with the data derived from the nucleotide sequence analysis.
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    Plant systematics and evolution 151 (1986), S. 163-174 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Briza ; Cluster analysis ; seed proteins ; electrophoresis ; grass systematics
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    Notes: Abstract The species ofBriza L. s. l. are disjunctly distributed between Eurasia and South America. A taxometric analysis has been carried out, using data from electrophoresis of seed polypeptides and published morphological characters. Evidence from a cluster analysis of seed polypeptide data strongly supports the recognition of two different natural groups, a S. American group and a Eurasian group, and is consistent with karyotype data, but does not support the generic groupings of South American taxa derived from the morphological data.
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    Plant systematics and evolution 151 (1986), S. 145-161 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Araceae.— Pollen nuclear number ; embryology ; evolution of trinucleate pollen ; irreversible evolutionary trend
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    Notes: Abstract Data on pollen nuclear number are presented for 74 of the 111 currently accepted genera of theAraceae — one of only three monocot families in which both bi- and trinucleate pollen are known to occur. Binucleate pollen, which characterizes 65% of aroid genera, is regarded as the primitive type inAraceae and monocots as a whole. The trend toward the trinucleate condition appears to be irreversible, and to have occurred many times within the family.Syngonium becomes the sixth angiosperm genus in which both character-states are known to occur; otherwise, the character is highly conservative at the generic level. Pollen nuclear number shows no evident correlation with pollen size, starch content or pollinator type.
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    Plant systematics and evolution 151 (1986), S. 215-222 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Gunneraceae ; Haloragaceae ; Hippuridaceae. — Sieve-element plastids ; ultrastructure and systematics
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    Notes: Abstract P-type sieve-element plastids were found in theGunneraceae, while S-type plastids are present in theHaloragaceae andHippuridaceae. The specific characters of the sieve-element plastids (e.g., their size and the morphology of their contents) are discussed in relation to other taxa of theRosidae containing P-type plastids and to the systematic position of theGunneraceae.
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    Plant systematics and evolution 151 (1986), S. 187-202 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Orchidaceae ; Thelymitra nuda ; Liliaceae ; Dichopogon ; Thysanotus ; Halictidae ; Lasioglossum ; Syrphidae. — Mimesis ; pollinaria ; staminodal hood ; thoracic vibration ; trichome cluster. — Flora of Australia
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    Notes: Abstract Insect pollination occurred inThelymitra nuda R. Br. on sunny days when the ambient temperature exceeded 20 °C. The flower buds on a raceme opened subsynchronously displaying the brightly-colored, actinomorphic perianth and exposed the contrastingly-colored, scented and ornamented column. InT. nuda the staminodes and the filament of the fertile stamen are fused to one another producing an inflated hood over the anther. This staminodal hood is terminated in two non-ornamental, but brightly-colored, central lobes and two terete lateral lobes bearing approximately 400 white trichomes. Each trichome bears a double chain of 30–40 spherical, rugulose cells. Female bees, in the genusLasioglossum (Halictidae), were observed to land directly on the hood and curled their bodies around the four lobed tip of the staminodal complex. The bees attempted to forage on the lobes as if they were collecting pollen from fertile, poricidal stamens. These bees applied thoracic vibration to the yellowish central lobes and actively scraped the trichome clusters (Pseudopollen) with their forelegs. Bees carried the pollinaria ofT. nuda dorsally on their abdomens. Abdominal contact with the rostellum appeared to occur when the female bee disengaged herself from the staminodal hood. Observations made of bees on co-blooming flowers, and analyses of pollen loads collected by bees suggested that the orchid flower mimics the guild of blue-purple flowers that lack floral nectar but offer pollen in poricidal anthers. The models ofT. nuda are co-bloomingLiliaceae in the generaDichopogon andThysanotus. However, nectarless, buzz-pollinated flowers are also extensively distributed over the orchid’s range. More than 30% of the flowers in theT. nuda population had their pollinaria removed, suggesting a high capacity for cross-pollination in an orchid genus usually considered to be self-pollinated via mechanical autogamy. This study confirmed previous predictions that column modifications represented a trend towards pseudanthery.
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    Plant systematics and evolution 151 (1986), S. 203-213 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Psathyrostachys juncea ; P. huashanica. — Chromosomes ; Giemsa ; C-banding patterns ; chromosome polymorphism ; nucleoli
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    Notes: Abstract The karyotypes ofP. juncea (Elymus junceus) andP. huashanica (both outbreeders) were investigated by Feulgen-staining and by C-, N-, and Agbanding, based on a single plant in cach case. Both species have 2n=2x=14 and large chromosomes, possibly a generic character. The karyotype ofP. juncea has 8 metacentrics and 6 SAT-chromosomes with minute, heterochromatic satellites while that ofP. huashanica has 9 metacentrics and 5 SAT-chromosomes only, 2 of which with small, heterochromatic satellites. The C-banding patterns ofP. juncea chromosomes comprise from one to five, mostly small, bands at distal, and terminal positions, while those ofP. huashanica chromosomes are characterized by large telomeric bands in most arms. Banding patterns and chromosome morphology allow identification of the homologues of the seven chromosome pairs inP. juncea, but of two pairs inP. huashanica only. The patterns of both taxa are polymorphic, supporting that both taxa are outbreeders. The karyotypic characters suggest thatP. juncea is more closely related toP. fragilis than either is toP. huashanica. N-banding stains weakly. Silver nitrate staining demonstrates that nucleolus organizers of both species have different nucleolus forming capacities. The presence of micronucleoli suggests that both species have an extra unidentified chromosome with nucleolus forming capacity.
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    Plant systematics and evolution 151 (1986), S. 223-228 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Hydrophyllaceae ; Nama. — Chemotaxonomy ; flavones ; 6-methoxy flavones ; C-glycosyl flavones
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    Notes: Abstract Eight flavonoids, four 6-oxygenated flavones, two methyl ethers of luteolin, apigenin 6,8-C-diglucoside and quercetin 3-O-glucoside, were isolated fromNama lobbii andN. rothrockii, sole members of sects.Arachnoidea andCinerascentia, respectively. Both taxa diverge markedly from other namas in morphology and chromosome number and their placement inNama has been questioned. The occurrence of 6-oxygenated flavones in these taxa adds to their already distinctive nature. Flavonoid evidence argues that both are more closely allied toEriodictyon than either is toNama.
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    Plant systematics and evolution 151 (1986), S. 229-239 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Asteraceae ; Astereae ; Osbertia ; O. chihuahua sp. n. ; Heterotheca ; Chrysopsis ; Pityopsis ; Noticastrum ; Erigeron ; Haplopappus. — Taxonomy. — Flora of Mexico
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    Notes: Abstract Osbertia, a stoloniferous group confined to the montane regions of Mexico and adjacent Guatemala, was first proposed as a genus byGreene (1895), but most workers have retained the taxon as part ofHaplopappus. It is clearly closer toNoticastrum, Erigeron orHeterotheca than it is toHaplopappus sensu stricto. The present treatment recognizes two species, a widespread highly variableOsbertia stolonifera and a newly describedO. chihuahuana from northwestern Mexico. Distribution maps, distinguishing features, full synonymy and illustrations are presented.
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    Plant systematics and evolution 151 (1986), S. 241-269 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Scrophulariacae ; Rhinanthoideae ; Euphrasia ; E. minima ; E. tatrae ; E. mendonçae ; E. willkommii. — Polyploid complex ; evolution of tetraploid species ; chorology and history of the Alpic flora ; new chromosome counts. — Flora of Europe ; of Turkey
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    Notes: Abstract A systematic analysis of the variable and probably allotetraploidE. minima is presented, its infraspecific taxonomy is discussed.E. tatrae is provisionally included intoE. minima although some differences may exist;E. mendonçae may be a relic of a formerly wider distribution ofE. minima; E. willkommii seems to be closer toE. stricta s. lat. than toE. minima. 4x-E. minima is supposed to be derived from phylogenetic lines close to extant dwarf alpine forms of 2x-E. alpina (including its yellow flowering subsp.christii;Vitek 1985b) and 2x-E. hirtella (vgl.Vitek 1985a). Some characteristics (e.g., its small flowers) could have been introduced through hybrid introgression from other 2x-species, particularlyE. inopinata and/orE. sinuata (vgl.Ehrendorfer & Vitek 1984).
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    Plant systematics and evolution 152 (1986), S. 47-48 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Lauraceae ; Ocotea ; Sex distribution ; dioecy ; Flora of South America
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    Notes: Abstract The evolution of dioecy inLauraceae cannot be attributed to selection for outbreeding but must have other reasons. Therefore it is interesting to note that inOcotea there seems to be a correlation between mode of reproduction and geographical distribution.
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    Plant systematics and evolution 152 (1986), S. 29-45 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Annonaceae ; Araceae ; Arecaceae ; Bignoniaceae ; Cyclanthaceae ; Magnoliaceae ; Malpighiaceae ; Malvaceae ; Nymphaeaceae ; Flowering phenology ; pollination strategies ; flower ecological radiation: neotropical savannas and forests ; melittophily ; nectar robbery ; “oil-flowers” and “oil-bees” ; ornithophily ; chiropterophily ; cantharophily:Dynastinae beetles ; flower evolution
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    Notes: Abstract Previously published data on flowering phenology and pollination of neotropical families are reviewed and compared with new observations, in order to evaluate some trends of pollination strategies in neotropical savannas and forests. Central American forestBignoniaceae apparently diminish competition between sympatric species with identical pollination strategies by alternating flowering. On the other hand, in theBignoniaceae of Brazilian cerrado savannas coincident flowering is more common, suggesting different pollination strategies. Bees specialized in nectar robbery are associated withBignoniaceae, particularly mass-flowering species. These nectar robbers stimulate pollinator movements between flowers and thus increase pollen-flow. The flowering phenology of theMalpighiaceae from forests and savannas apparently follows the phenology of theAnthophorinae (mainlyCentridini)-bees, on which this plant group almost exclusively depends for pollination in the Neotropics. As the flowers of different genera and species are very uniform, the bees quite indiscriminately pollinate coexistingMalpighiaceae taxa. In theMalvaceae, the more primitive tree or shrub habit and an allogamous reproduction system is quite significantly associated with an ornithophilous pollination mode. Hummingbirds in the Neotropics have probably influenced the origin of the primitive bird-pollinatedMalvaceae flower. In conjunction with the diversification of theMalvaceae and their migration into more open regions, pollination by bees has apparently become more prominent. ChiropterophilousMalvaceae seem to have developed more recently from ornithophilous ancestors within the neotropical forest regions. As a result of this ecological radiation, parallel modifications of the basic ornithophilous flower principle can be traced in different groups of theMalvaceae. Dynastinae-beetles are pollinators of South and Central American species ofAnnona, Cymbopetalum, Caladium, Talauma, Philodendron, Victoria, Nymphaea, Cyclanthus, Bactris and others. In many cases the relationship between flowers and theirDynastinae visitors is not very specific, principally reflecting differences in the faunistic spectrum of diverse regions and vegetation types. The attraction of these beetles as flower visitors in several unrelated groups of Angiosperms must have occurred repeatedly. It is suggested that the flower visiting species of this beetle group may have acquired their preference for certain pungent or aromatic flower odours by their feeding habits during the larval stage.
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    Keywords: Angiosperms ; Gymnosperms ; Cycadales ; Austrobaileyaceae ; Austrobaileya ; Sieve cells ; sieve tubes ; ultrastructure of sieve pores ; p-protein ; sieve-element terminology
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    Notes: Abstract The ultrastructure of the sieve elements ofAustrobaileya is compared with that of angiosperm sieve tubes and gymnosperm sieve cells (mostly fromCycadales). Except for the size of the sieve poresAustrobaileya shares all ultrastructural characters (e.g., chromatolytic nuclear degeneration, presence of p-protein, formation of sieve pores from unbranched plasmodesmata) and other features (e.g., companion cells) with angiosperm sieve tubes. Gymnosperm sieve cells on the contrary are characterized by pycnotic nuclear degeneration, absence of p-protein, formation of sieve areas from branched plasmodesmata with median cavities. — The exact ordinal assignment ofAustrobaileya within the subclassMagnoliidae is still disputed, a placement close to eitherMyristicaceae andWinteraceae orMonimiaceae being possible as judged from both S-type sieve-element plastids and p-protein bodies. — On the basis of the ultrastructural results fromAustrobaileya it is proposed to reconsider concepts and terminology of sieve elements. i.e., to include features from sieve pore development, nuclei degeneration and presence of specific proteins into the definitions and to restrict the term sieve cell to gymnospermous sieve elements which differ much from those of other vascular plants.
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    Plant systematics and evolution 152 (1986), S. 49-100 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Magnoliales ; Laurales ; Violales ; Malvales ; Chromosome numbers ; karyomorphology ; banding patterns ; polyploidy ; triploidy ; evolution and systematics in tropical woody plants
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    Notes: Abstract New karyological data are reported ofMagnoliidae, Violales, Malvales and some other orders. These data include for 102 species from 51 genera and 18 families chromosome counts, karyotypes, interphase nuclear structures and banding patterns. Karyomorphology suggests a new systematic arrangement for theLaurales (Fig. 11), a new circumscription of theCymbopetalum tribe (Annonaceae), and a placement of theCochlospermaceae/Bixaceae in theViolales. ForAnnonaceae andMagnoliidae x = 8 is proposed as the original base number. A model based on extant chromosome numbers inAnnonaceae and combining short dysploid series and polyploidization can explain most of the existing numbers in this family and in the otherMagnoliidae (Fig. 16). Special attention is drawn to the role of triploids and other anorthoploids in chromosome number diversification (e.g., inAnnonaceae, Apocynaceae, Proteaceae). Identical polyploid numbers are shown to have originated from different base numbers. The highest chromosome number forMagnoliidae is found inMyristicaceae (Osteophloeum: 2n = 280). Polyploid relic genera frequently exhibit highly differentiated and “diploidized” karyotypes with many structural rearrangements. The step diploid polyploid is correlated in several genera with the invasion from humid to more extreme, often xeric habitats. Polyploidy serves as a crossing barrier in related syntopic species. InAnnonaceae, Cochlospermaceae andMyristicaceae neotropical taxa have a higher polyploidization rate than palaeotropical ones. — Subsequential fluorochrome-and Giemsa C-banding demonstrates the following pattern for tropical woody plants: Chromosomes mostly have neutral (neither AT- nor GC-rich) proximal heterochromatin (= hc), intercalarly and/or terminal bands are rare. In some cases great variation occurs in regard to location and composition of bands between the investigated taxa. Differences concern genera, species groups or species. Diploid karyotypes tend to contain less different hc-types than polyploid ones. NO-chromosomes also exhibit a remarkable banding pattern differentiation. In general, hc-variation is greater in respect to composition than to distribution.
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    Plant systematics and evolution 152 (1986), S. 123-131 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Asteraceae ; Dendrosenecio ; Age determination ; ecophysiology ; phylogeny ; population dynamics
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    Notes: Abstract The genusDendrosenecio (“giant groundsels”), encompassing three species and 12 subspecies, is endemic to the high mountains of East and Central Africa where it constitutes the most conspicuous components of the afroalpine vegetation. Two lifeforms, the arborescent and the prostrate rhizomatous, are regarded as the results of evolution from forest-living woody or herbaceous ancestors. Due to the uninterrupted growth period in the tropics, there are no anatomical or morphological features which allow conventional age determination. However, stem elongation rates have been determined (3–5.5 cm per year) and indicate an age of about 250 years for the tallest arborescent Dendrosenecios which may reach a height of 10 m. 30 to 120 large leaves are clustered in an enormous terminal rosette, justifying the term “giant rosette” plants. A leaf bud, consisting of about as many developing leaves as the rosette contains, is found in the center. During the nocturnal frost period the adult rosette leaves form a so-called night-bud by nyctinastic upwards bending and thus protect the leaf bud from freezing by insulation. The stem is surrounded by a mantle of persistent dead leaves; this ameliorates the microclimate of the pith-cells which greatly contribute to water transport into the leaves. Below the leaf rosette a zone of putrefaction is found, from where the decay of the dead leaves apparently provides nutrients directly to the growing stem. The population dynamics of the arborescentD. keniodendron is characterized by a simultaneous inflorescence development at irregular intervals of up to more than twenty years. Due to sporadic flowering and a seedling survival rate of less than 1%, oscillations of the population size are to be expected.
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    Plant systematics and evolution 152 (1986), S. 153-166 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Festuca ; Evolution ; seed proteins ; electrophoresis
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    Notes: Abstract Seed protein electrophoresis of four chromosomes races ofFestuca arundinacea, F. mairei and their progenitors showed variation in banding patterns. High protein similarities betweenF. arundinacea, F. mairei, F. scariosa, andF. pratensis indicate close phylogenetic relationships of these species. The ancestry ofF. arundinacea cytotypes could be narrowed to three diploid species:F. scariosa, F. pratensis, andF. rubra or to their close relatives.
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    Plant systematics and evolution 152 (1986), S. 133-151 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Cucurbitaceae ; Luffa cylindrica ; L. acutangula ; Benincasa hispida ; Coccinia indica
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    Notes: Abstract DNA sequence organization patterns have been studied in fourCucurbitaceae plant species, namely,Luffa cylindrica (sponge gourd),L. acutangula (ridge gourd),Benincasa hispida (ash gourd) andCoccinia indica (ivy gourd). Extensive interspersion of repeat and single copy sequences has been observed in sponge gourd and ridge gourd. In ash gourd and ivy gourd, however, there is a limited interspersion of these sequences and a large portion of the single copy DNA remains uninterspersed. The interspersed repetitive sequences are composed of a major class (75–80%) of short repeats (300 base pairs long) and a minor class (15–20%) of long repeats (2 000–4 000 base pairs) in all the four species. The average length of single copy sequences dispersed among repeats is 1 800–2 900 base pairs. In spite of these gross similarities in the genome organization in the four species, the fraction of repeats and single copy sequences involved in short and long period interspersion patterns, and fraction of single copy sequences remaining uninterrupted by repeats are vastly different. The probable implications of these differences with respect to speciation events and rates of genome evolution are discussed.
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    Plant systematics and evolution 152 (1986), S. 167-183 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Lamiaceae ; Sideritis ; Meiotic behaviour ; karyotypes ; size and fertility of pollen grains ; DNA values ; seed protein electrophoresis ; phylogenetic relationships
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    Notes: Abstract Six closely related taxa of the sect.Eusideritis of the genusSideritis (S. leucantha, S. pusilla, S. flavovirens, S. granatensis, S. biflora andS. osteoxylla) are analysed to elucidate their phylogenetic relationships and position within the sect.Eusideritis. Meiotic behaviour, karyotype features, size and fertility of pollen grains, DNA amounts and seed protein profiles are reviewed. A polyploid origin of the group (from x = 7) and the further diversification through dysploidy and chromosome repatterning is postulated.S. osteoxylla is apparently of hybrid origin.
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    Plant systematics and evolution 152 (1986), S. 185-194 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Asclepiadaceae ; Calotropis procera ; Xylocopa ; Pollen germination ; nectar concentration ; robbery by ants ; Flora of Israel
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    Notes: Abstract Calotropis procera (Asclepiadaceae) grows in Israel under extremely hot climatic conditions. Flower morphology is adapted towards the concealment of nectar, in order to protect it against robbery by ants and from evaporation. Pollinia while being inserted within the stigmatic chamber, are soaked in the liquid nectar which, by its concentration controls pollen germination. Two Carpenter bees (Xylocopa) are the only pollinators and their behavior on flowers is discussed.
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    Plant systematics and evolution 152 (1986), S. 211-218 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Rosaceae ; Malachobatus ; Rubus ; Taxonomy ; crossing experiments ; apomixis ; chromosome numbers
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    Notes: Abstract A review of current knowledge of chromosome numbers and modes of reproduction in the genusRubus L. is presented. Chromosome numbers from some species of subg.Malachobatus Focke together with results of crossing experiments are reported for the first time.
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    Plant systematics and evolution 152 (1986), S. 219-230 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Cyperaceae ; Scleria foliosa ; Embryology: endosperm haustoria ; cotyledon ; systematics
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    Notes: Abstract The embryology ofScleria foliosa A. Rich. is described and several features have been recorded for the first time in the family. The endosperm having both micropylar and chalazal haustoria and embryo with characteristic cotyledon bearing papillate outgrowths are unique features noted in this taxon. The epicotylary and cotyledonary sectors are adjacently placed and occupy a terminal position on the embryonic axis. Taxonomic implications of the embryological findings with particular reference to the problem of circumscription ofScleria are discussed.
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    Plant systematics and evolution 152 (1986), S. 195-210 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Asteraceae (Compositae) ; Anthemideae ; Artemisia ; Chromosome banding ; heterochromatin ; karyosystematics
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    Notes: Abstract Detailed C-banded karyotypes of eight diploidArtemisia species from three different sections are reported together with preliminary observations on three additional related diploid species. In the majority, the overall amount of banding is relatively low. Bands are mostly confined to distal chromosome regions; intercalary banding is virtually absent and centromeric heterochromatin is also scarce. With the exception ofA. judaica there is in general great uniformity in karyotype structure but considerable interspecific variation in total karyotype length (and hence DNA content) ranging from 44 µm inA. capillaris (2n = 18) to 99 µm inA. atrata (2n = 18).A. judaica (2n = 16; total karyotype length 97 µm) was distinguished by its karyomorphology, with one large non-banded metacentric chromosome pair and 7 pairs of smaller terminally banded meta- or submetacentric chromosomes.
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    Plant systematics and evolution 152 (1986), S. 231-241 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Dilleniaceae ; Hibbertia fasciculata ; Lasioglossum (Halictidae) ; Leioproctus (Colletidae) ; Myrtaceae ; Bees ; beetles ; floral symmetry ; stamens ; stigmas
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    Notes: Abstract In direct contrast to mostHibbertia spp., the flowers ofH. fasciculata R. Br. ex D. C. bear only a single whorl of stamens and these stamens are arranged separately (not in typical “bundles”). The short filaments are appressed to the three carpels so that the inflated, porose and introrsive anthers form a centralized cluster obscuring the three ovaries. The three slender styles emerge at right angles from between the filaments. These styles curve upward and the stigmas form the three points of a triangle; each stigma is approximately one millimeter outside the centralized cluster of anthers. The flowers are nectarless and bear a bright yellow corolla. A pungent and unpleasant fragrance appears to be concentrated within the pollenkitt. When native bees attempt to forage for the pollen, within the cluster of anthers, the ventrally deposited loads of pollen, on the bees' abdomens, contact the outer triangle of stigmas. The major pollinators ofH. fasciculata are female bees in the polylectic genera,Lasioglossum (subgenusChilalictus, Halictidae) andLeioproctus (Colletidae). These bees carry an average of more than two pollen taxa when they are caught foraging onH. fasciculata. 78% of the 47 bees, captured onH. fasciculata carried the pollen from at least one sympatric taxon bearing nectariferous flowers (e.g., genera in theMyrtaceae, Compositae, andEpacridaceae). The pollination biology ofH. fasciculata is assessed in relation to the known radiation of bee-pollinated flowers in the genusHibbertia, and within theDilleniaceae s. l.
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    Plant systematics and evolution 152 (1986), S. 267-276 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Plumbaginaceae Dyerophytum africanum ; D. indicum ; Ceratostigma abyssinicum ; Linum ; Distyly ; dimorphic pollen ; exine sculpturing
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    Notes: Abstract Light and SEM observations on the pollen ofDyerophytum africanum andD. indicum have revealed marked differences in exine features. These distylous species also have dimorphic pollen. In the short-styled individuals of both species, the sexine and nexine are of equal thickness, and the clava-like sexinous processes are short without marked projections. In the long-styled individuals, the sexine is thicker than the nexine, the clavae are higher than broad with an apical spinule. Pollen size and apertures are identical in both morphs. — Palynological evidence is presented for relationships betweenDyerophytum andCeratostigma, Plumbago andAegialitis. Moreover, the genusDyerophytum exhibits pollen morphological similarities with some species ofLinum (Linaceae).
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    Plant systematics and evolution 152 (1986), S. 277-296 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Cruciferae ; Capsella bursa-pastoris ; Adaptation ; inception of flowering in natural populations ; phenotypic and genotypic variability
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    Notes: Abstract Seed samples were collected from wild populations ofCapsella bursa-pastoris along a transsect from Northern to Southern Europe. Progeny was grown in (a) open-field random block experiments (47 populations) and (b) in growth chambers under five to seven controlled temperature regimes (18 populations). Beginning of flowering was recorded, and great differences between and also within populations are documented. Some populations are extremely heterogenous whereas others are homogenous in this respect. Some biotypes react positively when exposed to lower temperatures, others are inhibited. In many cases specific effects of day- and/or night-temperatures can be inferred. In some progenies begin of flowering is independent of temperature as long as this exceeds the 5:10°C regimen. Altogether,Capsella bursa-pastoris displays definite intraspecific variation in time required until flowering. Adaptations to local ecological conditions are obvious. In addition to a genotypic component pronounced environmental interactions provide the plants with a component of phenotypic plasticity. The degree of modificability apparently varies itself and seems to be controlled by selection; the phenotypic plasticity, therefore, displays adaptive variation patterns, too.
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    Plant systematics and evolution 153 (1986), S. 1-5 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Fabaceae ; Trigonella ; fenugreek ; Karyotype ; C-banding ; evolution
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    Notes: Abstract The six species of the sectionFoenum-graecum ofTrigonella have the same chromosome number, 2n = 16.T. gladiata andT. cariensis have fairly symmetrical karyotypes, while those ofT. foenum-graecum, T. berythea, T. macrorrhyncha andT. cassia are asymmetrical. C-bands are present in all six species but the number of bands and their positive vary considerably among the species. The karyotype evidence suggests that none of the available species of theFoenum-graecum section can be considered as the wild progenitor of fenugreek.
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    Plant systematics and evolution 153 (1986), S. 7-12 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Vulpia sectt.Loretia ; Vulpia Monachne ; Morphology ; seed protein electrophoresis ; numerical systematics
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    Notes: Abstract Seven species ofVulpia were subjected to morphological and protein studies using principal component and cluster analysis and theJaccard's Similarity Coefficient. Studies showed all species were uniform and distinct from each other. Species of sect.Loretia were very dissimilar from those of sect.Monachne and sect.Vulpia. The latter section comprises taxa of high mutual affinity.
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    Plant systematics and evolution 153 (1986), S. 31-36 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Hydrocharitaceae ; Limnobium spongia ; Somatic chromosome number ; karyotype analysis ; Limnobium versusHydromystria
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    Notes: Abstract The somatic chromosomes ofLimnobium spongia have been studied for the first time. Its number is 2n = 24; the karyotype is composed of 5 m pairs + 3 sm pairs + 4 st pairs. Pairs 3 and 11 bear microsatellites. Results are compared with previous chromosome reports for the family, mainly as regards the taxonomic status ofLimnobium versusHydromystria; our findings seem to support the point of view of those who favour the independence of both generic entities.
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  • 53
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    Keywords: Angiosperms ; Poaceae ; Triticum dicoccoides ; Uredinales ; Puccinia striiformis ; Wild emmer ; pathogene resistances ; ecology ; allozyme genotypes ; statistic analyses ; Flora of Israel
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    Notes: Abstract From 114 accessions of wild emmer wheat from 11 sites in Israel, known for their allozymic variation (Nevo & al. 1982), individual genotypes were tested for resistance to one isolate of stripe rust both in the seedling stage in a growth chamber and in the adult plant stage in the field. The results indicate that resistance to stripe rust in seedlings and adults are significantly correlated (rs = 0.40, p 〈 0.001). Genetic polymorphisms of resistance to stripe rust vary geographically and are predictable by climatic, as well as allozymic markers. Three variable combinations of rainfall, evaporation, and temperature explain significantly 0.40–0.53 of the spatial variance in disease resistance to stripe rust, suggesting the operation of natural selection. Several allozyme genotypes are significantly associated with disease resistance. We conclude that natural populations of wild emmer wheat in Israel contain large amounts of disease resistance genes. These populations could be effectively screened and then utilized by the phytopathologist for identifying resistant genotypes and producing new resistant cultivars.
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    Plant systematics and evolution 153 (1986), S. 49-64 
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    Keywords: Angiosperms ; Poaceae ; Hordeum spp. ; Interspecific hybridization ; relationships
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    Notes: Abstract A crossing programme including 30 species and 40 cytotypes within the genusHordeum was undertaken. Viable hybrids were obtained in 302 combinations, 15 of which were intraspecific. Differences in seed set and in germination were observed in crosses between different groups of species. Obtaining crosses between different taxonomic groups was generally more difficult when diploid material was used. Some species, e.g.,H. lechleri, H. jubatum, andH. brachyantherum showed a higher crossability than others. The chromosome numbers of the hybrids were usually those expected from the parental numbers but aneuploid series around the expected numbers were rather frequent. Three cases of unreduced gametes were found. Selective chromosome elimination was restricted to combinations including eitherH. vulgare orH. bulbosum.—Despite a very diverse morphology, all South American diploid species together with the two North American diploidsH. intercedens andH. pusillum appear to be closely related. The hexaploid American speciesH. procerum, H. lechleri, andH. arizonicum are also related. The two North American tetraploid speciesH. jubatum andH. brachyantherum sometimes form semifertile hybrids. The Asiatic speciesH. roshevitzii appears to be related to both North and South American taxa.
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    Plant systematics and evolution 153 (1986), S. 65-76 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Orchidaceae ; Prasophyllum odoratum ; Pollination ecology
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    Notes: Abstract Prasophyllum odoratum is a vernal, nectariferous, terrestrial orchid that flowers profusely six to eight months following cyclical fires that disrupt sclerophyll woodlands. The morphology of the column and pollinarium is indicative of taxa placed within the subfam.Spiranthoideae. The orientation of the pollinaria to the stigma appears to prevent mechanical self-pollination. Both cross- and self-pollination appear to be effected by insects that forage within the brightly-colored, scented, non-resupinate flowers. Ants and drosophilid flies remove nectar, but do not appear to transport pollinaria between flowers. The primary pollinators are polytrophic flies in the fam.Syrphidae and opportunistic male bees in the genusLeioproctus (Colletidae). Approximately 52% of the flowers on a raceme set seed. The comparatively short floral tube ofP. odoratum reflects the dependence of this species on short-tongued insects to effect successful dispersal of pollinaria.
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    Plant systematics and evolution 153 (1986), S. 133-139 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Lactoridaceae ; Lactoris ; Flavonoids ; evolution
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    Notes: Abstract Leaves of the monotypic angiosperm familyLactoridaceae exhibit flavonoid constituents consisting of six 3-0-diglycosides of the flavonols kaempferol and isorhamnetin. The presence of flavonols is concordant with the placement ofLactoridaceae among the “archaic” or “primitive” flowering plants. Flavonoid chemistry is less informative on the relationships of the family within the primitive dicots. The presence of isorhamnetin suggests closer affinities with families in theLaurales, particularly theGomortegaceae andMonimiaceae. Phenetic and cladistic analyses of morphological features place theLactoridaceae near several families in theMagnoliales.
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    Plant systematics and evolution 153 (1986), S. 165-170 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Araceae ; Amorphophallus nicolsonianus ; species nova ; Flora of India
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    Notes: Abstract Amorphophallus nicolsonianus species nova, with cylindrical or napiform corms, is the only representative of the sect.Rapyogkos in India. All the other hitherto known species of this region have globose or depressed globose corms. The new species is related to some Indochinese species and toA. hildebrandtii ( Engl.)Engl. & Gehrm. from Madagascar.
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    Plant systematics and evolution 153 (1986), S. 141-164 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Hordeum spontaneum ; Genetic resources ; allozyme polymorphism ; correlation with environmental parameters ; Flora of Iran
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    Notes: Abstract Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267−0.500, and of genetic diversity,He = 0.134, range = 0.069−0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02−0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted.
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    Plant systematics and evolution 153 (1986), S. 181-197 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Hordeum murinum complex ; wild barley ; Classification ; numerical methods ; conditional clustering
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    Notes: Abstract The purpose of this paper is to produce a classification of theHordeum murinum complex. Using an experimental design to account for the environmental component of the phenotypic variation, material from sources throughout the old-world range ofH. murinum was grown in a common environment. Eight morphological characters were measured on the resulting triplets (i.e., the central and lateral florets, glumes and rachis internode). Clustering, variance and discriminants analyses of these data suggest that there are three distinct groups. This classification is then examined for consistency with hypotheses obtained from the work of other researchers and discussed in light of the known biology of the plants. An identification key to members of the complex using the triplet characters is provided.
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    Plant systematics and evolution 153 (1986), S. 199-204 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Iridaceae ; Crocus sativus L. ; Chromosome number ; karyotype analysis ; meiosis ; univalents ; bivalents ; trivalents ; laggard chromosomes ; inversions ; sterility
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    Notes: Abstract Meiosis and mitosis are described in cultivatedCrocus sativus of Iran. This indicates that this species is an autotriploid and sterile. Karyotype analysis, rare inversions, laggard chromosomes and distribution of chromosomes in the first anaphase are described, and the reasons for its sterility are given.
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    Plant systematics and evolution 153 (1986), S. 223-227 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Leguminosae ; Caesalpinioideae ; Cassia ; Habit ; DNA content ; evolution
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    Notes: Abstract Ten species of the genusCassia show a range of 2C DNA amounts from 1.30 to 2.54 pg at the same ploidy level. Remarkably, a distinct 2-fold increase is depicted by an arboreal speciesC. excelsa while the rest comprising of herbs, trees and shrubs have a range from 1.30 to 1.47 pg. These form a natural grouping with respect to mean DNA amounts which differ by 0.05 pg in the herbs, trees and shrubs respectively.
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    Plant systematics and evolution 153 (1986), S. 205-222 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Geraniaceae ; Pelargonium ; Chromosome numbers ; karyotypes ; hybrids ; karyotype evolution ; taxonomy
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    Notes: Abstract The chromosome numbers of seven species ofPelargonium sect.Eumorpha have been determined from material of known wild origin, and karyotypic comparisons have been made. Within the section there is variation in basic chromosome number (x = 4, 8, 9, 11), variation in chromosome size, and two species have polyploid races. The three species with chromosome numbers based on x = 11 have the smallest chromosomes (1.0–1.5 µm); chromosomes are larger (1.0–3.0 µm) in the other species.P. elongatum has the lowest chromosome number in the genus (2n = 8).P. alchemilloides is exceptional in that it has four cytotypes, 2n = 16, 18, 34 and 36, and the form with 2n = 36 has large chromosomes (2.0–5.0 µm). Evidence from a synthesized hybrid suggests thatP. alchemilloides with 2n = 16 may be of polyploid origin. The three species based on x = 11 appear to be more closely related to species from other sections ofPelargonium that have the same basic chromosome number and small chromosome size, rather than to other species of sect.Eumorpha.
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    Keywords: Angiosperms ; Orchidaceae ; Orchis ; Interspecific hybrids ; species identification ; enzyme electrophoresis
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    Notes: Abstract The European orchidsOrchis mascula, O. pallens and their hybrids have been analysed by enzyme electrophoresis on starch gels. The two species differ in the electrophoretic mobilities of four out of eight enzymes tested. Three enzymes, phosphoglucomutase, phosphoglucoisomerase and “malic enzyme” exhibit typical heterozygote patterns in the hybrid plants demonstrating the presence of both differing parental alleles. Thus, species identification is easy by the electrophoretic analysis of a low number of enzyme loci, and hybrids are detectable even if morphological characters fail.
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    Plant systematics and evolution 153 (1986), S. 243-258 
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    Keywords: Angiosperms ; Linaceae ; Linum tenuifolium L. ; L. suffruticosum L. ; L. salsoloides Lam. ; L. appressum Caballero ; Variation ; phenetics ; systematics ; evolution
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    Notes: Abstract The phenetic variation inL. tenuifolium s.l. was assessed using multivariate analyses of 27 characters found to be variable within the species. These results are discussed and interpreted in the context of the reproductive biology, chromosome number and ecological responses of the taxa. Evidence suggests that both the self-compatible and tetraploid races were derived independently from a self-incompatible, diploid type. Although no taxonomic scheme is compatible with all of the evidence presented, the study supports a recent decision to recognize four taxa at subspecific level.
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    Plant systematics and evolution 153 (1986), S. 259-264 
    ISSN: 1615-6110
    Keywords: Gymnosperms ; Angiosperms ; Pteridosperms ; Caytoniales ; Caytonanthus ; Ultrastructure ; pollen
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    Notes: Abstract The pollen grain wall structure ofCaytonanthus arberi was studied with SEM and TEM. The monosulcate, bisaccate pollen grain of this taxon has an alveolar wall structure that is more like that found in saccate Conifers than primitive Angiosperms. Pollen grain morphology does not support a Caytonialean ancestry for the Angiosperms.
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    Plant systematics and evolution 153 (1986), S. 281-285 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Brassicaceae ; Brassica ; Electrophoresis of complete Rubisco ; systematics ; evolution
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    Notes: Abstract A simple electrophoretic technique for separating Rubiscoholoenzyme (ribulose bisphosphate carboxylase-oxygenase) from crude extracts is introduced. No preliminary purification steps are required. To prove the validity of the technique we rely on well studiedBrassica spp., tobacco and spinach. We recommend this method for studies concerned with intrageneric relationships and for proving the intraspecific constancy of Rubisco.
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    Plant systematics and evolution 153 (1986), S. 265-279 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Cruciferae (= Brassicaceae) ; Capsella bursapastoris ; C. rubella ; C. grandiflora ; Adaptation ; growth form parameters ; phenotypic and genotypic variability
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    Notes: Abstract Growth form parameters ofCapsella bursa-pastoris populations, including a wide range of different environments, have been analyzed from random block field and growth chamber experiments. Changes in one character are often correlated with changes in another. Of special interest are correlations detected with the onset of first flowering. Variation in each of the characters is clearly influenced by both phenotypic and genotypic components. However, genotype — environment interactions are also subject to variation. Therefore, the adaptive significance of a given parameter is not found to be constant over the entire geographical range of the genus. Alpine populations tend to shift from annual to biannual life cycles.
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    Plant systematics and evolution 153 (1986), S. 287-292 
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    Keywords: Angiosperms ; Liliaceae ; Gagea ; New Species ; Flora of Iran ; Afghanistan ; Pakistan
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    Notes: Abstract Six new species are described:Gagea anonyma, G. Staintonii, G. siphonantha, G. Grey-Wilsonii, G. chloroneura. All belong to subgen.Platyspermum (Boiss.)Miscz.
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    Plant systematics and evolution 154 (1986), S. 1-10 
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    Keywords: Angiosperms ; Liliaceae ; Urginea maritima ; Pollination mechanisms
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    Notes: Abstract Three co-existing pollination mechanisms are found inUrginea maritima: insect-, wind-, and self-pollination. The flowers exhibit a typical insect-pollination syndrome; they offer abundant exposed nectar as well as pollen. Out of the many different visitors only a few could be regarded as pollinators:Apis mellifera, Polistes gallicus, andVespa orientalis. Wind pollination also occurs and generally is responsible for self-pollination. It is argued that the development of extra wind-pollination accompanied by partial self-incompatibility is an adaptation to increase pollination in an unfavourable season (August–September), when insects are scarce.
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    Plant systematics and evolution 154 (1986), S. 31-39 
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    Keywords: Angiosperms ; Lactoridaceae ; Ultrastructure ; pollen ; fossil pollen (Cretaceous)
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    Notes: Abstract The pollen wall ultrastructure of the primitive AngiospermLactoris fernandeziana Phil. (Lactoridaceae) is described. The monosulcate aperture, granular wall structure and sacci (all primitive features) suggest placement of this family in theMagnoliales. Pollen ofLactoris is compared to fossil dispersed pollen from the Lower and lower-Upper Cretaceous. The fossil pollen shares characteristics which are restricted to theLactoridaceae suggesting that this family was present during the early Cretaceous.
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    Plant systematics and evolution 154 (1986), S. 11-30 
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    Keywords: Angiosperms ; Apiaceae ; Karyology ; NOR ; nucleolus ; nucleolar bivalents ; NOR evolution
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    Notes: Abstract Data available for the nucleolus organizing region in the familyApiaceae are reviewed. An attempt has been made to establish the exact number of this region in various subfamilies and tribes through studies on the karyotype and nucleolus. Most of the taxa have a single nucleolar chromosome per haploid complement. The location of the nucleolar organizing region (NOR) on the chromosome varies. Members ofHydrocotyloideae differ drastically from those of subfam.Saniculoideae andApioideae, with respect to the location of NOR. Despite wide geographical distribution, varied ecological preferences and differences in morphology, anatomy and cytology, Umbellifers have attained stability in the number and location of NORs. Characters of NOR offer scope for utilization in understanding phylogenetic relationships at higher levels of taxonomic hierarchy.
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    Plant systematics and evolution 154 (1986), S. 41-61 
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    Keywords: Angiosperms ; Liliaceae ; Fritillaria graeca ; Phytogeography ; statistics ; systematics ; Flora of Greece
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    Notes: Abstract The geographic variation inFritillaria graeca, an endemic of Greece, is explored, using multivariate techniques. Eleven morphological features were measured in each of 630 individual plants from 38 localities throughout the range of the species.Scheffe's a posteriori test revealed an almost continuous geographic variation and did not identify groups clearly. Discriminant analysis of the groups derived from an F significance test ofMahalanobis distance resulted in five major groups on the first two discriminant axes representing the subspeciesgraeca, ionica, guicciardii, thessala and its var.othria. A diagnostic key to theF. graeca subspecies is provided.
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    Plant systematics and evolution 154 (1986), S. 79-88 
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    Keywords: Angiosperms ; Onagraceae ; Oenothera sect ; Oenothera subsect ; Oenothera ; Oe. wolfii ; Chromosomal analysis ; plastid analysis ; complexheterozygosity ; taxonomy
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    Notes: Abstract Oenothera wolfii, endemic in coastal Northern California and Southern Oregon, has been analysed cytogenetically. It is a permanent structural heterozygote composed of two nearly identical genomic complexes which are closely related to the neighboring maritime ecotype of the homozygousOe. elata subsp.hookeri. — Oe wolfii is believed to have evolved recently from its homozygous ancestor by the accumulation of reciprocal translocations and the acquisition of balanced lethals. Forms such asOe. wolfii represent an important connecting link in our understanding of the evolution of the complexheterozygous species ofOenothera.
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    Plant systematics and evolution 154 (1986), S. 63-77 
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    Keywords: Angiosperms ; Cucurbitaceae ; Cucumis melo ; C. sativus ; Cucurbita pepo ; C. maxima ; Ribosomal RNA genes ; restriction enzymes ; evolutionary aspects
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    Notes: Abstract Cucurbitaceae are characterized by a high copy number for nuclear ribosomal RNA genes. We have investigated the genomic ribosomal DNA (rDNA) of four closely related species of this family with respect to structure, length heterogeneity, and evolution. InCucumis melo (melon) there are two main length variants of rDNA repeats with 10.7 and 10.55kb.Cucumis sativus (cucumber) shows at least three repeat types with 11.5, 10.5, and 10.2kb.Cucurbita pepo (zucchini) has two different repeat types with 10.0 and 9.3kb. There are also two different repeat types inCucurbita maxima (pumpkin) of about 11.2 and 10.5kb. Restriction enzyme mapping of the genomic rDNA of these four plants and of cloned repeats ofC. sativus shows further heterogeneities which are due to methylation or point mutations. By comparison of the restriction enzyme maps it was possible to trace some evolutionary events in the family ofCucurbitaceae. Some aspects of regulation and function of the middle repetitive rRNA genes (here between 2000 and 10000 copies) are discussed.
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    Plant systematics and evolution 154 (1986), S. 89-101 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Onagraceae ; Oenothera hookeri ; Oe. biennis ; Oe. suaveolens ; Megaspore tetrads ; inheritance of polarity of embryo sac development
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    Notes: Abstract In the F2-progeny of hybrids from crosses betweenOenothera biennis orsuaveolens andOe. hookeri with theRenner-complexesalbicans andhhookeri, the development of callose pattern in meiocytes and megaspore tetrads is the same as in the F1 and the parentOe. hookeri. During the development of the megaspore tetrads and the embryo sacs primary and secondary heteropolarity as well as homopolarity is observed. Estimates for the initial frequency of homo- and heteropolar tetrads at the end of the degeneration of megaspores in the tetrads immediately before the start of embryo sac development could be calculated. The F2-plants can be arranged in three groups, distinguished by the frequency of the two polarity types. One of these groups behaves similar to the parentOe. hookeri, the two others have more homopolar tetrads. The segregation can be interpreted as recombination of genes, which influence the development of the polarity in the ovules. This is possible by crossing-over of genes between the twoRenner-complexes of the hybrid.
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  • 76
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    Plant systematics and evolution 154 (1986), S. 103-110 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Liliaceae ; Hyacinthaceae ; Ornithogalum ; subg.Beryllis ; O. narbonense ; O. pyrenaicum ; O. sessiliflorum ; Numerical taxonomy ; systematics ; Flora of Morocco
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In North Africa,Ornithogalum L. subg.Beryllis Baker is represented by three taxa (O. narbonense L.,O. pyrenaicum L., andO. sessiliflorum Desf.), often difficult to identify. 90 individuals from 4 localities were subjected to a biometric study based on 19 morphological characteristics. Several types of multivariate analyses allow a perfect identification of the three species. Studies on the reproductive biology, cytotaxonomy, and ecology supplement these data.
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    Plant systematics and evolution 154 (1986), S. 111-128 
    ISSN: 1615-6110
    Keywords: Angiosperms ; new taxa ; Flora of Turkey ; of Greece
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A total of 25 items are listed. 16 are new taxa described from South and East Anatolia:Papaver (1),Heldreichia (1),Astragalus (1),Lotus (1),Onobrychis (3),Sempervivum (2),Hellenocarum (1),Cirsium (2),Campanula (1),Omphalodes (1),Allium (1) andPuccinellia (1). Nine other species belonging to the generaDiplotaxis, Beta, Acacia, Lupinus, Cirsium, Limonium, Calamagrostis andPuccinellia, are new records for the Flora of Turkey area. Two combinations are made, one inPapaver (p. 113), the other inHellenocarum (p. 122).
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  • 78
    ISSN: 1615-6110
    Keywords: Angiosperms ; Paeoniaceae ; Paeonia tenuifolia ; Hyacinthaceae ; Ornithogalum flavovirens ; Synaptonemal complex ; surface-spreading
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    Notes: Abstract A modified method for obtaining surface spread synaptonemal complexes (SCs) from pollen mother cells has been developed. Silver-stained SC-preparation of one monocotyledonous species,Ornithogalum flavovirens, and one dicotyledonous plant,Paeonia tenuifolia, were analysed by light and electron microscopy. The SCs in both species frequently broke into roughly equally sized SC pieces with staggered or blunt breakpoints. The telomeric ends of the SCs normally were lacking attachment organelles and, therefore, were hardly distinguishable from blunt breakpoints. Interstitially, shorter stretches of SCs often exhibited unpaired lateral elements. This phenomenon is discussed with regard to segmental incomplete homology and as it relates to the normal sequence of SC morphological changes during the course of meiotic prophase.
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  • 79
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    Plant systematics and evolution 154 (1986), S. 137-145 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Caryophyllales ; Stegnospermataceae ; Stegnosperma halimifolium ; S. watsonii ; Embryology ; systematic position and affinities
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    Topics: Biology
    Notes: Abstract The embryology ofStegnosperma halimifolium andS. watsonii has been studied in detail. The tapetum is of the secretory type and its cells become multinucleate. Simultaneous cytokinesis in the pollen mother cells follows meiosis. The ripe pollen grains are 3-celled. The ovule is crassinucellate, bitegmic and amphitropous, with the micropyle formed by the inner integument alone. The female archesporium is one celled, and the parietal tissue 3–5 layered. The embryo sac development conforms to thePolygonum type. A central strand, 6 or 7 cells thick, differentiates inside the nucellus and extends from the base of the embryo sac to the chalazal region. The endosperm is nuclear. The embryogeny conforms to the Caryophyllad type. The seed coat is formed by the outer epidermis of the outer integument and the inner epidermis of the inner integument. Based on this evidence and other data, the status of the genus as an independent family,Stegnospermataceae (Stegnospermaceae) is confirmed. Apparently, it forms a connecting link betweenPhytolaccaceae andCaryophyllaceae.
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  • 80
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    Plant systematics and evolution 154 (1986), S. 175-182 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Festuca ; Ovinae ; Bovinae ; Scariosae ; Montanae ; Morphology ; protein electrophoresis ; numerical systematics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Morphological and seed protein studies of selected species ofFestuca were performed to elucidate the relationships between species of sect.Ovinae and their affinity with other fescues.Festuca rubra andF. heterophylla (extravaginale group) had higher phenetic affinity with taxa of sect.Scariosae, Montanae andBovinae than with members of their own section. 5 species of the intravaginale group (F. ovina, F. capillata, F. valesiaca, F. sulcata, F. trachyphylla) were fairly uniform and well defined by protein and morphological data. This supports current systematic thinking and does not agree withHackel's (1882) classification of this group.
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    Plant systematics and evolution 154 (1986), S. 147-173 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Magnoliidae ; Annonaceae ; Tetrameranthus ; Cleistopholis ; Rollinia ; Annona ; Chromosome numbers ; karyotypes ; banding patterns ; interphase nuclei ; karyoevolution in tropical woody plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract First generic chromosome counts reveal the base number x=7 for the generaTetrameranthus andRollinia. T. umbellatus from the Peruvian Amazon is diploid (2n=14),T. duckei from Brazil (Manaus) is tetraploid (2n=28). In the NeotropicsRollinia (7 species counted) has developed diploid to octoploid taxa (2n=14, 28, 42, 56). Counts of 7 South AmericanAnnona species are presented for comparison (2n=14, 28). The West AfricanCleistopholis patens has 2n=14. The Asian genusMezettia: 2n=14 and the neotropicalGuatteria tribe: 2n=28 are also revised. A detailed karyomorphological comparison, including karyotypes, banding patterns, condensing behaviour of chromosomes and structure of interphase nuclei reveals that the closely related generaAnnona andRollinia are almost identical in their diploid genomes, whereas the polyploid ones differ in their heterochromatin (=hc) composition and number of NO-chromosomes.Cleistopholis, Mezettia and theGuatteria tribe are karyologically and systematically distinct from each other and fromAnnona/Rollinia. Tetrameranthus as compared with the karyomorphology of about 60 other Annonaceous genera has a very peculiar and unusual karyomorphology which underlines its isolated position. Nuclear structures are almost identical in the African genusUvariopsis (2n = 16) and partly similar in theGuatteria tribe; both also share some morphological similarities and possibly are related. From a comparison ofTetrameranthus with several nuclear types within theMagnoliidae, a new model of chromosome evolution in primitive Angiosperms is suggested. In respect to their eco-morphological differentiation the genera investigated differ strongly from each other.
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    Plant systematics and evolution 154 (1986), S. 183-194 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Triticum aestivum ; T. timopheevi ; Chromosomes ; C-banding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The somatic chromosomes ofTriticum timopheevi and those of two varieties ofT. aestivum, “Chinese Spring” and “Bezostaya-1”, have been identified by a Giemsa staining technique. The data suggest thatT. timopheevi and tetraploid wheats had a common ancestor from which their genomes differentiated due to chromosomal aberrations and the increase of heterochromatin in the chromosomes of theT. timopheevi G-genome. The differences between the chromosomes of the AB and AG genomes result in substitutions and large translocations between these chromosomes in interspecific hybrids.
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    Plant systematics and evolution 154 (1986), S. 237-250 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Bignoniaceae ; Deplanchea ; Morphology ; inflorescence ; flower ; nectar ; pollination ; evolution ; Flora of Malesia ; Australia
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    Topics: Biology
    Notes: Abstract The reproductive structures ofDeplanchea tetraphylla (Bignoniaceae) exhibit a significant number of unusual features: inflorescence with an apical “platform”; flowers yellow, short-tubed, strongly zygomorphic; mouth closed through lateral compression; stamens and style long-exserted, erect or slightly reclined; nectar dark brown, exposed in the spoon-shaped lowermost corolla lobe and apparently acting also as a visual cue. These features suggest a highly elaborate syndrome for bird pollination: the birds (probably lorikeets) perch on the inflorescence platform and bend downwards to take up the exposed nectar, thus touching the exserted anthers and stigmas with the throat or breast. The likely evolution of this syndrome by additive steps, effecting a change from “head up” to “head down” position of the pollinator, can be traced from the floral structure of the remaining four species of the genus.
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    Plant systematics and evolution 154 (1986), S. 251-257 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Gramineae ; Triticum ; Leaves ; tricin derivatives ; schaftoside ; iso-orientin O-glycosides ; chemosystematics ; origin of bread wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf flavonoids have been identified in seven species ofTriticum, all of which have been considered at one time as putative parents of the cultivated tetraploid and hexaploid wheats. The major constituents are apigenin- and luteolin-based glycosylflavones, some of which contain various O-glycosidic attachments at the 6″-position. Four tricin glycosides are present in minor amount, as is free tricin. The flavonoid patterns link togetherT. searsii, T. speltoides andT. squarrosa, on the one hand, andT. monococcum, T. boeoticum, T. thaoudar andT. urartu, on the other. These results indicate that the first three taxa are more likely to be diploid ancestors to the hexaploidT. aestivum than the latter four species.
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    Plant systematics and evolution 154 (1986), S. 259-274 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Paeoniaceae ; Paeonia tenuifolia ; P. officinalis ; Synaptonemal complex ; surface-spreading ; chromosome banding ; silver staining ; nucleolus organiser region ; karyotype analysis
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    Topics: Biology
    Notes: Abstract The meiosis of the diploidPaeonia tenuifola and the allotetraploidP. officinalis was studied after conventional methanol/acetic acid-fixation and synaptonemal complex (SC) spreading. Meiosis inP. tenuifolia (2n = 10) is normal with five bivalents in metaphase I, and the SCs in pachytene show regular features. InP. officinalis (2n = 4x = 20) univalents, bivalents and multivalents are found in metaphase I. The SCs reveal several abnormalities: a high number of unpaired lateral elements, partner exchanges between three and four lateral elements, loops and lateral element thickenings. These characteristics are compared with the situations found in other polyploid and hybrid species. It is noteworthy that the abnormalities in meiosis ofP. officinalis are not reflected in its somatic karyotype. Its features were analysed after silver staining and fluorescent staining with chromomycin and compared with those ofP. tenuifolia.
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    Plant systematics and evolution 154 (1986), S. 275-283 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Leguminosae-Papilionoideae ; Vigna ; V. vexillata ; Hymenoptera-Anthophoridae ; Xylocopa ; Pollination ; Flora of Costa Rica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pollination ofVigna vexillata (Leguminosae-Papilionoideae) by a carpenter bee,Xylocopa gualanensis (Hymenoptera-Anthophoridae) was studied in a secondary vegetation in Costa Rica. The bees were observed foraging onV. vexillata only in early mornings. Visits on individual flowers lasted about 7–8 seconds. Flower—pollen vector interactions are described and illustrated. By its pressure on the left-hand wing- and keel-petal in the asymmetrical flower, the weight of the bee causes the upper bearded part of the style along with the upper free parts of the stamens to slip out of the rigid keel-beak, “hugging” the bee over the dorsal part of its head and thorax. The occurrence of nototribic pollination inVigna and related genera is discussed.
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    Plant systematics and evolution 154 (1986), S. 285-323 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Self-incompatibility ; homomorphic SI ; heteromorphic SI ; sporophytic SI
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    Topics: Biology
    Notes: Abstract The view put forward by some authors that flowering plant self-incompatibility mechanisms of the homomorphic sporophytic and heteromorphic sporophytic types have a close evolutionary relationship, with one form being evolved from the other, or both forms directly evolved from ancestors with homomorphic gametophytic incompatibility, is challenged. A review is provided of the various facets of each of the three main self-incompatibility systems, including a detailed summary of our current knowledge of the rejection mechanism, to demonstrate that the implicit assumption that these systems have a common S locus, and also evolutionary theories linking the systems, need to be treated with considerable caution.
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    Plant systematics and evolution 154 (1986), S. 343-366 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Rubiaceae ; Spermacoceae ; Phylohydrax ; gen. nov. ; P. carnosa ; P. madagascariensis ; Hydrophylax ; H. maritima ; Flora of Southern Africa ; Flora Zambesiaca ; Flora of Tropical East Africa ; Flore de Madagascar et des Comores ; Flora of India ; Flora of Sri Lanka ; Flora of Thailand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydrophylax, a genus of maritime strand or dune plants, was previously thought to comprise three species, one from India, Sri Lanka and Thailand (H. maritima), and two from Africa and Madagascar (“H.” carnosa and “H.” madagascariensis respectively). Evidence is presented that the African and Madagascan species are better placed into a separate genus (Phylohydrax). Differential characters betweenH. maritima andP. carnosa—P. madagascariensis, the relationships between the three species, and the affinities ofPhylohydrax andHydrophylax to otherSpermacoceae are discussed in detail.
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    Molecular genetics and genomics 202 (1986), S. 120-124 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Ribosomal protein ; Edeine resistant mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The r-proteins of an edeine-resistant mutant of Saccharomyces cerevisiae were compared to those of the wild-type strain by using two different two-dimensional electrophoretic techniques: (1) the Kaltschmidt-Wittmann method and, (2) the Kaltschmidt-Wittmann system, in the first dimension and the Na Dodecyl-SO4 system in the second. With the first technique, the results indicate that the patterns of basic ribosomal proteins are similar in the two strains. However, the pattern of acidic ribosomal proteins of the mutant revealed an additional protein band with respect to the normal one. Using the other technique, the patterns of basic and acidic ribosomal proteins of the mutant demonstrated a similarity to the corresponding pattern of the wild-type strain. The data disclose that an acidic ribosomal protein of the mutant may have two forms with different electrophoretic mobilities and similar molecular weights.
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    Molecular genetics and genomics 202 (1986), S. 421-428 
    ISSN: 1617-4623
    Keywords: Recombination intermediates ; Mitochondrial DNA ; Electron microscopy ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To study the structure of in vivo mitochondrial DNA recombination intermediates in Saccharomyces cerevisiae, we used a deletion mutant of the wild type mitochondrial genome. The mtDNA of this petite is composed of a direct tandem repetition of an ∼4,600 pb monomer repeat unit with a unique HhaI restriction enzyme site per repeat. The structure of native mtDNA isolated from log phase cells, and mtDNA crosslinked in vivo with trioxsalen plus UVA irradiation, was studied by electron microscopy. Both populations contained crossed strand “Holliday” type recombination intermediates. Digestion of both non-crosslinked and crosslinked and mtDNA with the enzyme HhaI released X and H shaped structures composed of two monomers. Electron microscopic analysis revealed that these structures had pairs of equal length arms as required for homologous recombination intermediates and that junctions could occur at points along the entire monomer length. The percentage of recombining monomers in both non-crosslinked and trioxsalen crosslinked mtDNA was calculated by quantitative analysis of all the structures present in an HhaI digest. The relationship between these values and the apparent dispersive replication of mtDNA in density-shift experiments and mtDNA fragility during isolation is discussed.
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  • 91
    ISSN: 1617-4623
    Keywords: Excision repair ; denV gene ; UV radiation ; Saccharomyces cerevisiae ; Phage T4
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    Topics: Biology
    Notes: Summary The denV gene of bacteriophage T4 was reconstituted from two overlapping DNA fragments cloned in M13 vectors. The coding region of the intact gene was tailored into a series of plasmid vectors containing different promoters suitable for expression of the gene in E. coli and in yeast. Induction of the TAC promoter with IPTG resulted in overexpression of the gene, which was lethal to E. coli. Expression of the TACdenV gene in the absence of IPTG, or the use of the yeast GAL1 or ADH promoters resulted in partial complementation of the UV sensitivity of uvrA, uvrB, uvrC and recA mutants of E. coli and rad1, rad2, rad3, rad4 and rad10 mutants of S. cerevisiae. The extent of denV-mediated reactivation of excision-defective mutants was approximately equal to that of photoreactivation of such strains. Excision proficient E. coli cells transformed with a plasmid containing the denV gene were slightly more resistant to ultraviolet (UV) radiation than control cells without the denV gene. On the other hand, excision proficient yeast cells were slightly more sensitive to killing by UV radiation following transformation with a plasmid containing the denV gene. This effect was more pronounced in yeast mutants of the RAD52 epistasis group.
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    Molecular genetics and genomics 204 (1986), S. 98-102 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Minichromosomes ; Centromere ; Copy number ; Mitotic stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transformation of Saccharomyces cerevisiae with several yeast CEN4 ARS1 plasmids containing the his3-Δ4 allele (as well as the URA3 and TRP1 markers) yielded His+ transformants at 0.1%–50% the frequency of Ura+ Trp+ transformants. Additional His+ derivatives arose on continuous growth of transformants originally scored as His- Ura+ Trp+. In all cases, the His+ phenotype was not due to plasmid or host mutations but invariably correlated with an up to 12-fold increase in plasmid copy number. On removal of selective pressure, the His+ phenotype was lost more readily than the Ura+ Trp+ markers, with a corresponding decrease in plasmid copy number. Also, the amplification did not decrease the mitotic loss rate of the Ura+ Trp+ markers. These results indicate that CEN ARS plasmids can be spontaneously amplified to higher levels than previously observed. However, when amplified, apparently not all copies exhibit the characteristic stability of CEN ARS plasmids.
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    Molecular genetics and genomics 204 (1986), S. 496-504 
    ISSN: 1617-4623
    Keywords: Heterothallic mating type switching ; Saccharomyces cerevisiae ; RAD52 ; RAD3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mating type interconversion of the yeast Saccharomyces cerevisiae is mediated by intrachromosomal gene conversion. Whereas homothallic switching is initiated by an endonuclease that produces a DNA double-strand cut within MAT, heterothallic strains lack this activity. In order to identify functions essential for initiation and realisation of heterothallic switching, repair-deficient strains carrying the rad52 or the rad3 mutation were constructed and tested for spontaneous and induced heterothallic switching frequencies. The wild type RAD52 function is essential for spontaneous and induced switching as well as for the intrachromosomal crossing over which produces a deleted ring chromosome III. The rad3 mutation had almost no influence on spontaneous or X-ray induced switching, but it does reduce induction by ultraviolet radiation. The data are interpreted to indicate that heterothallic switching is accomplished via recombinogenic repair, perhaps of a double-strand break. The conversion event as well as the crossing over event leading to a change in mating type are equally affected by the rad52 mutation and therefore perhaps associated.
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    Molecular genetics and genomics 204 (1986), S. 310-316 
    ISSN: 1617-4623
    Keywords: Gene replacement ; PGI1 deletion ; Glucose-6-P ; Glucose dependence ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The structural gene PG11 coding for phosphoglucose isomerase was replaced by the LEU2 gene in the genome of Saccharomyces cerevisiae. Plasmids carrying the LEU2 gene between genomic regions flanking the PG11 gene were constructed and used to transform a PGI1/pgi1 diploid strain. Stable transformants lacking the PGI1 allele were isolated. Southern analysis of their meiotic products showed that haploid strains with a deletion of 1.6 kb within the 2.2 kb PG11 coding region were viable. Thus, the PGI1 gene is not essential in yeasts. However, unlike pgi1 mutants with residual phosphoglucose isomerase activity, no growth was detected in the pgi1Δ haploid strains when fructose was supplied as sole carbon source. The wild-type growth rate could be restored by adding 0.1% glucose to the medium. Furthermore, pgi1 mutants with residual enzymatic activity grew very slowly on fructose-supplemented media containing up to 2% glucose. Strains carrying the deletion allele, however, failed to grow at glucose concentrations higher than 0.5%. Also the pgi1Δ strains did not grow in glucose as sole carbon source. On the other hand pgi1Δ/pgi1Δ diploid strains did not sporulate on the usual acetate medium. This defect could be alleviated by the addition of 0.05% glucose to the sporulation medium. Under these conditions the pgi1Δ mutants sporulated with an efficiency of 25% compared with the wild type. These results suggest that (a) the phosphoglucose isomerase reaction is the only step catalysing the interconversion of glucose-6-P and fructose-6-P, (b) glucose-6-P is essential in yeasts, and (c) the oxidation of glucose-6-P through the glucose-6-P dehydrogenase reaction is not sufficient to support growth in yeasts.
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  • 95
    ISSN: 1617-4623
    Keywords: Centromere ; In vitro mutagenesis ; Mitosis ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Centromeres most likely consist of DNA (CEN DNA) interacting with specific proteins. In Saccharomyces cerevisiae a clear picture has emerged of a 120 bp sequence that is characteristic of CEN DNA. We have investigated the 25 bp centromere DNA element (CDEIII) that represents the right part of a CEN DNA. We showed using a series of mutants generated in vitro that the right most triple A of the consensus sequence TGT.T.TG.. TTCCGAA.....AAA participates in the assembly of a functional centromere and that no further sequences to the right are needed. Distance changes between the centre dyad TTCCGAA and the triple A have two effects: Addition of one base pair leads to a reduction, and addition of two or four base pairs to a loss of centromere function implying a participation of the centre dyad and the triple A region in protein binding. Indeed, a synthetic ologonucleotide of 39 bp containing CDEIII shows specific protein binding.
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    Journal of industrial microbiology and biotechnology 1 (1986), S. 187-193 
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Cytochromec ; Superoxide dismutase ; Catalase ; Oxyradicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two strains ofSaccharomyces cerevisiae were used to study the synthesis of superoxide dismutase. One strain (cytochromec-deficient) contained 5–10% of the normal amounts of total cytochromec, while the other strain was a wild type. The cytochromec-deficient mutant had lower specific growth rate, growth yield, and oxygen uptake than the wild type. The superoxide dismutase and catalase activities, in both strains, were significantly lower under anaerobic than under aerobic conditions. Furthermore, under aerobic conditions the mutant contained higher levels of superoxide dismutase than the wild type which may be attributed to the higher intracellular flux of superoxide radicals caused by the cytochromec deficiency. The mutant also showed a lower level of catalase which was due to glucose repression.
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