Bamboo and BVOCs: Exploring the interplay between isoprene emission and physiology

Background/Question/Methods

Biogenic volatile organic compounds (BVOC) are emitted from plant leaves and play a significant role in ecological interactions, protection from abiotic and biotic stresses, and regional atmospheric chemistry. Though BVOCs comprise a minor proportion of a plant’s photosynthetic carbon, they are the most significant and abundant source of VOCs globally. BVOCs are emitted in a diverse number of forms with equally diverse functions throughout plant taxa. Isoprene is the most abundant non-methane BVOC emitted, and has a significant impact on ozone formation and depletion of peroxide radicals. Isoprene emission is well-constrained within most groups of plants, but displays variable emission within the bamboos. We have found that bamboos emit a broad range of BVOCs in addition to isoprene, which may differentially impact their physiology. Thus, we have identified bamboos as a novel system for studying the interplay that occurs between isoprene and all other BVOCs, as well as elucidating physiological factors that vary alongside isoprene emission.

Results/Conclusions

Here we present comparisons of physiological parameters relative to isoprene emission rate, and within the context of the diverse range of BVOCs emitted by bamboos. In a common garden field study, physiological measurements were made on 16 phylogenetically dispersed species of bamboo with variable levels of isoprene emission (0-33 nmol isoprene m^-2 sec^-1). ANOVAS were used to compare physiological parameters to the relative amount of isoprene emitted by each species (high, medium, low). No significant difference was found between isoprene emission level and photosynthetic rate, electron transport rate, or stomatal conductance. Dark respiration rate was significantly different amongst isoprene types, and was highest in plants with medium emission rates. Additionally, total BVOC composition was measured in the lab following the field survey. Our previous work has shown broad diversity in BVOCs emitted in bamboos, and that this variability is partially due to variations in isoprene emission. Here, we show that emissions of sesquiterpenes, compounds that serve plants in biotic and ecological interactions, are significantly reduced in plants that make high levels of isoprene. Taken together, this data suggest that there are biochemical trade-offs that track isoprene emission level and significantly effect the physiology and BVOC composition of this system.