When my collaborator Dr. Li Xin from the Tea Research Institute (TRI) in Hangzhou, China decided to spend a semester in the Orians lab at Tufts, we decided this would be a good opportunity to make use of the Boston Area Climate Experiment (BACE) to do some work on tea and drought stress. BACE is an experiment started by Jeff Dukes at Purdue University to study the effects of climate change on plant communities. We thought it would be a good tool to study the effects of drought and insect herbivory on tea plants.
There are already quite a few studies on how drought stress affects tea plants and how insect herbivory affects tea plants, but fewer studies that investigate the interaction. We also have the ability to measure hundreds of metabolites in tea thanks to the efforts of our collaborators in the Robbat lab. This offered a great opportunity to better understand the response of tea plants to herbivory under different degrees of drought stress.
We manipulated rainfall in the BACE plots by using corrugated poly carbonate roofing slats at different spacing to create plots that got either 100%, 75%, or 50% of ambient rainfall. We planted tea plants in these plots and after a summer of growing in these three precipitation regimes, we treated half of the plants with methyl jasmonate, a plant hormone used to mimic insect herbivory, and measured photosynthesis, volatile metabolites, and non-volatile secondary metabolites.
Changes in volatiles were induced by MeJA only in the 100% rainfall treatment, indicating that drought stress inhibits the inducibility of volatiles by simulated herbivory. Non-volatiles were not affected by drought or simulated herbivory in this experiment.