Vladimir OSSIPOV-1,2, Erkki HAUKIOJA-1;, Sinikka
HANHIMAKI-1,2, Kalevi PIHLAJA-2
Laboratory of Ecological Zoology-1 and Laboratory of
Physical Chemistry-2, University of Turku, FIN - 20014, Turku, Finland
We studied the biochemical basis of resistance of the mountain birch, Betula pubescens ssp. tortuosa, to larvae of the autumnal moth, Epirrita autumnata. Relative growth rate (RGR) of larvae was measured on leaves from 40 individual trees and, on the basis of these data, 15 of the worst (RGR, 0.250 ± 0.028) and 15 of the best trees (RGR, 0.342 ± 0.021) for E. autumnata were chosen for further biochemical analysis. We used as biochemical indices of leaf quality the following leaf traits: contents of soluble and cell wall bound proanthocyanidins, gallotannins, protein precipitating activity of tannins, total phenolics and 36 individual phenolic compounds (1, 2), water content, total nitrogen, carbohydrates (glucose, fructose, galactose, sucrose and inositol), acetone insoluble residue and toughness of leaves. We also analysed correlations between larval growth rate and biochemical traits of foliage.
Leaves from trees of poor quality (PQ) as food for E. autumnata had a significantly higher concentration of soluble proanthocyanidins and galactose than leaves from good quality trees (GQ). Differences in other leaf parameters were not significant. Negative correlation was found between E. autumnata RGR and leaf toughness of PQ trees (r = -0.69, P = 0.004). Instead, larval RGR was not correlated with leaf tpoughness in GQ trees. Activity of protein precipitation (APP) correlated positively with total content of gallotannins in leaves of both tree categories (PQ, r = 0.54, P = 0.035; GQ, r= 0.71, P = 0.003). We did not find correlation between APP and soluble proanthocyanidins although concentration of foliage condensed tannins was about 4-5 times higher than that of gallotannins.
On the basis of these data, the role of different groups of phenolic compounds, primary metabolites and components of cell wall in the mechanism of birch - herbivore relationships will be summarized and discussed.
Literature