SPECIES-SPECIFIC COMPOSITION OF FREE AMINO-ACIDS ON THE LEAF SURFACE OF 4 SENECIO SPECIES

The specificity of the chemical composition of the leaf surface of fou r Senecio species was studied in order to understand the host selectio n of Tyria jacobaeae, a monophagous moth that has Senecio jacobaea as its principal host plant. Pyrrolizidine alkaloids characteristic for S enecio species were not detected in water and sulfuric acid extracts o f the leaf surface of Senecio jacobaea. Water extracts of the leaf sur faces of S. jacobaea, S. vulgaris, S. viscosus, and S. sylvaticus cont ained low concentrations of free amino acids. The proportions of these amino acids were very different from those inside the leaf tissues. I n a discriminant analysis, the four species could be completely separa ted on the basis of the relative proportions of amino acids on the lea f surface.