Isoprene is more affected by climate drivers than monoterpenes: a meta-analytic review on plant isoprenoid emissions

Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatileorganic compounds produced by plants (biogenic volatile organic compounds). Weconducted a meta-analysis to quantify the mean effect of environmental factorsassociated to climate change (warming, drought, elevated CO2, and O3) on the emis-sion of isoprene and MTs. Results indicated that all single factors except warminginhibited isoprene emission. When subsets of data collected in experiments run undersimilar change of a given environmental factor were compared, isoprene and photo-synthesis responded negatively to elevated O3(-8% and-10%, respectively) anddrought (-15% and-42%), and in opposite ways to elevated CO2(-23% and +55%)and warming (+53% and-23%, respectively). Effects on MTs emission were usuallynot significant, with the exceptions of a significant stimulation caused by warming(+39%) and by elevated O3(limited to O3-insensitive plants, and evergreen specieswith storage organs). Our results clearly highlight individual effects of environmentalfactors on isoprene and MT emissions, and an overall uncoupling between thesesecondary metabolites produced by the same methylerythritol 4-phosphate pathway.Future results from manipulative experiments and long-term observations may helpuntangling the interactive effects of these factors and filling gaps featured in thecurrent meta-analysis