Direct and interactive effects of light availability and insect herbivory on inducibility of chemical defences in young pine trees

Abstract

Plants have evolved plastic responses to face the multiple stressors they have to cope with, such as light availability and insect herbivory. The former may impact the ability of producing induced defenses in response to herbivory due to conflicts in the allocation of C resources in absence of photosynthesis, and also because light may directly modulate the plant immune system. Here we hypothesized that pine tree induced responses to herbivory may depend on light availability during herbivore attack. Using a time course design we studied pine defensive responses to herbivory by the large pine weevil in 3 pine tree species under light deprivation. Plants in dark of the 3 species were significantly more consumed than control plants, and all them increased their resin concentration proportionally to the damage received by the weevil along time. Contrarily to our expectations, light deprivation did not decrease the inducibility of chemical defences in young pine trees.