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1991 (1)
1984 (1)
1Author    Michael WinkRequires cookie*
 Title    Chemical Defense of Lupins. Mollusc-Repellent Properties of Quinolizidine Alkaloids  
 Abstract    Polyphagous molluscs such as H elix pom atia and Arion rufus generally do not feed on plants containing alkaloids. O f 19 species tested 10 species were totally avoided, the other 9 species were less attacked than Lactuca sativa, which was readily taken. Plants containing quinolizidine alkaloids were studied in detail. Those species with the a-pyridone alkaloids cytisine and N-methylcytisine were avoided to a higher extent than plants with lupanine as the major alkaloid. Since the repellency observed could be due to other natural products present in the plants besides the alkaloids, the feeding response o f H elix pom atia was tested on artificial diets containing quinolizidine alkaloids in various concentrations as the only variable. If the snails had the choice they clearly preferred alkaloid-free food or a diet with only low alkaloid concen­ trations. Half-maximal repellency o f cytisine is less than 2 m M , o f sparteine 1 -5 m M , and o f lupanine 1 -8 mM. Since the in vivo concentrations o f sparteine, cytisine, and lupanine are equal to or higher than the inhibitory concentrations required it is concluded that quinolizidine alkaloids constitute a potential antimolluscan principle o f legum es. 
  Reference    Z. Naturforsch. 39c, 553 (1984); received March 22 1984 
  Published    1984 
  Keywords    Quinolizidine Alkaloids, M ollusc Repellency, C oevolution, Plant-H erbivore Interaction, Snails, Chemical Defense 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0553.pdf 
 Identifier    ZNC-1984-39c-0553 
 Volume    39 
2Author    M. Assim, DiG. IulioRequires cookie*
 Title    On the Relationships between the Genetic Code Coevolution Hypothesis and the Physicochemical Hypothesis  
 Abstract    This paper analyzes the relationships between the genetic code coevolution hypothesis and the physicochemical hypothesis by means o f a comparative study o f the precursor-product amino acid pairs on which the former hypothesis is based. Even if the coevolution between the biosynthetic relationships o f amino acids and the organization o f the genetic code is not ques­ tioned in this paper, the results and the arguments used lead us to believe that the selective pressures considered essential by the physicochemical postulates, played a more active role than that o f the precursor-product relationships in defining the allocation o f these amino acids in the genetic code. It is furthermore pointed out that the two evolutionary hypothesis might be aspects o f the same selective pressure, and thus difficult to differentiate. 
  Reference    Z. Naturforsch. 46c, 305 (1991); received September 28 1990 
  Published    1991 
  Keywords    Genetic Code Theories, C oevolution, Precursor-Product Amino Acids, Am ino Acids Proper­ ties, Hypergeometric Distribution 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0305.pdf 
 Identifier    ZNC-1991-46c-0305 
 Volume    46