Spruce needle compounds and the susceptibility of Norway spruce (Picea abies Karst.) to attacks by the European sawfly, Gilpinia hercyniae Htg. (Hym., Diprionidae)
1989
Schopf, R. (Muenchen Univ. (Germany, F.R.). Lehrstuhl fuer Angewandte Zoologie)
Interaction of Norway spruce (Picea abies Karst.) with European spruce sawfly (Gilpinia hercyniae Htg.) (Hym., Dipronidae) was used to characterize the susceptibility of a tree to the attack by a defoliating insect, on the basis of the concentrations of particular needle compounds. The hypothesis tested was that rather varying concentrations of a highly toxic compound control the development of the sawflies than the actual steady state concentrations of several primary and secondary plant compounds. Larvae of G. hercyniae were raised on physiologically different plant material and the developmental characters larval mortality, period of larval development cocoon weight, and egg number were determined. Simultaneously, the concentrations of the following needle compounds were measured: glucose, fructose, sucrose, inisitol, pinitol, picein, protein-bound amino acids, shikimic and quinic acid, p-hydroxy acetophenone, catechin gallocatechin and the fraction of the soluble phenols. Supported by a multiple regression analysis exponential functions of the general form y Y(Max) (1-e(-XDP) were described which allow prediction of the developmental success of G. hercyniae (y) on the basis of an estimated maximum value of a developmental parameter (Y(Max)) and the determined concentrations of the spruce needle compounds (X(DP)) on a significant level. The term X(DB) represents a linear expression (X(DP) = ax1 + bx2 -cx3 + ... x0) in which the concentrations of the needle compounds are evaluated by the sign and the absolute value of the corresponding coefficients (a, b, c, etc.). Already published physiological data concerning plant-herbivore-systems and especially Norway spruce-G. hercyniae indicate that the results obtained by the statistical procedure are biologically plausible
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