Interactive effects of drought severity and simulated herbivory on tea (Camellia sinensis) volatile and non-volatile metabolites

Abstract

Plants often experience multiple sources of stress simultaneously, yet little is known about interactive effects of multiple stressors on plant metabolic responses. Plants are well known to respond to both drought and insect herbivory through the induced production of secondary metabolites. However, severe drought stress limits photosynthesis and may therefore inhibit the production of induced secondary metabolites in response to herbivory due to carbon limitation. On the other hand, drought-stressed plants may be primed to respond more strongly to herbivory due to hormonal crosstalk or redundancy of metabolites that are produced in response to drought and herbivory. We tested the interactive effects of drought and simulated herbivory in tea plants (Camellia sinensis (L.) Kuntze var. sinensis) grown in the field under varying rainfall interception treatments and then exposed to an exogenous methyl jasmonate (MeJA) treatment.We show that severe drought generally inhibits the induction of secondary metabolites by exogenous MeJA (simulated herbivory). However, a few volatile metabolites, including methyl salicylate, are more strongly induced by MeJA in severely drought-stressed plants compared to moderately stressed plants, possibly due to priming by drought stress. Our approach of using multiple levels of drought stress and a targeted/untargeted approach to measuring volatile metabolites was essential to discovering these patterns of induction. In addition to having implications for plant-herbivore interactions in the presence of abiotic stress, these results have important implications for tea quality.