Systemic induction of salicylates in Salix myrsinifolia (Salisb.)

Abstract

We studied the induction of salicylates in mature leaves of Salix myrsinifolia Salisb. (Salicaceae) following severe wounding by a specialist leaf-beetle Phratora vitellinae L. (Chrysomelidae). Levels of individual salicylates and aromatic amino acids and their total levels were determined in leaves at different developmental stages. Induction of salicylates depended on: (1) the individual compound; (2) the developmental stage of the plant organ; and (3) the genotype of the plant. Induction of salicylates was systemic: levels of salicylates rose in unwounded young immature and mature leaves, but no local response was detected in wounded leaves. In addition, there were clear clonal variations in both the constant and induced levels of salicylates: clones with the highest levels of salicylates were also most capable of increasing this level in response to herbivore attack i.e. no trade-off between constant and induced levels was detected. Furthermore, the levels of three aromatic amino acids, Phe, Tyr and Trp, increased in immature leaves of herbivore-affected plants, which may indicate induction of enzymes of the shikimate pathway by wounding. The increase in salicylates was suggested to be a consequence of an increased rate of synthesis rather than that of translocation. The induced levels of salicylates did not affect the subsequent feeding of highly specialized P. vitellinae. However, the ability to increase levels of salicylates may reduce grazing by generalist herbivores which are not able to tolerate high levels of salicylates. © 2001 Annals of Botany Company.