Physiological and compensatory growth responses of Jatropha curcas (L.) seedlings to simulated herbivory and drought stress

Abstract

We investigated the physiological and growth responses of Jatropha curcas (L.) seedlings to simulated herbivory stress at different levels of drought stress in experimental greenhouse conditions. Simulated herbivory stress had an effect on photosystem II (PSII) yield of seedlings. The highest decrease of mean PSII yield (63 %) was recorded in seedlings grown under severe drought stress (200 mm yr−1) whereas a moderate herbivory stress (25 %) showed positive effects on mean PSII yield of the seedlings grown under well-watered conditions (1,900 mm yr−1). Stem water content, stem dry biomass and root–shoot ratio (with or without leaves) were significantly affected by the interaction effect of the simulated herbivory and drought stress. Simulated herbivory stress had effects on both root biomass and autumnal height growth rate. The highest above- and below-ground biomasses were obtained in the undamaged and well-watered (1,900 mm yr−1) seedlings, whereas the lowest above- and below-ground biomass were obtained in seedlings exposed to 25 % herbivory stress and grown in extreme drought stress (200 mm yr−1). Our results showed that J. curcas seedlings exhibited under-compensatory growth responses to simulated herbivory stress in all drought stress levels.