Ernesto GIANOLI. Hermann M. NIEMEYER
Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de
Chile, Casilla 653, Santiago, Chile
Seedlings of the wild wheat Triticum uniaristatum L. showed a significant increase in their levels of hydroxamic acids (Hx) following controlled infestation by the aphid Rhopalosiphum padi (L.) in comparison with uninfested seedlings. Given that Hx levels were analysed only in the infested tissue (primary leaf), it could not be ascertained whether the induced response was a consequence of enhanced local synthesis of Hx or the significantly less costly translocation of Hx from uninfested organs. Since each of these physiological processes involves quite different metabolic costs, it was considered that an experimental discrimination between them would allow predictions on the existence of phenotypic costs (expressed in fitnessrelated parameters) of such induced responses in T uniaristatum.
The induction experiment was performed again, this time extending the analysis of Hx to the secondary leaf, stem and root. Results obtained supported the hypothesis of translocation of Hx from uninfested organs, and hence suggested a lack of phenotypic costs of the induced responses This was later confirmed by determining no significant differences in growth, rate of leaf production, age at tillering stage, biomass at 4 months, and mortality between infested and uninfested plants.
These results show, in agreement with earlier suggestions, that patterns of resource allocation in plants at a physiological level may be related to patterns at an ecological level.