Wound-induced plant responses and their consequences for insect grazing

Gibberd, Ruth Margaret (1987) Wound-induced plant responses and their consequences for insect grazing. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The aims of this thesis were to examine the consequences of rapid wound-induced changes in plant chemistry for insect feeding behaviour, and to investigate the hypothesis that such changes are defensive. The two main tree species used were alder Alnus glutinosa and hawthorn Crataegus monogyna. Laboratory based palatability experiments demonstrated that following artificial damage, the palatability of A. glutinosa and C. monogyna leaves, parts of leaves and leaves adjacent to damaged leaves to a polyphagous Lepidoptera Spodoptera littoralis was reduced. This wound-induced plant response was most marked at the beginning of the season, in young leaves and 1-2 days after damage. A study was made of the leaf phenology of A. glutinosa and C. monogyna. Field studies were also conducted to investigate the seasonal and temporal distributions of insect grazing on these tree species. The total nitrogen and total soluble phenol concentrations of damaged and undamaged A. glutinosa and C. monogyna leaves were examined through the growing season. In general phenol concentrations increased in artificially damaged leaves and in leaves adjacent to them. Laboratory experiments demonstrated that artificial damage to Betula pendula leaves affected the behaviour of a polyphagous Lepidoptera Orthosia stabilis. Orthosia stabilis larvae confined on damaged leaves were more active than larvae confined on undamaged leaves. The mechanisms by which plants may benefit from rapid wound-induced responses and the role which canopy heterogeneity plays in the defensive strategy of plants against insect herbivores are discussed. The evidence presented here for A. glutinosa and C. monogyna suggests that these species may have an evolved antiherbivore defence. (D76174/87)