Abstract
Isoprene (C5H8) is a hydrocarbon gas emitted by many tree species and has been shown to protect photosynthesis under abiotic stress. Under optimal conditions for photosynthesis, ~70%–90% of carbon used for isoprene biosynthesis is produced from recently assimilated atmospheric CO2. While the contribution of alternative carbon sources that increase with leaf temperature and other stresses have been demonstrated, uncertainties remain regarding the biochemical source(s) of isoprene carbon. In this study, we investigated leaf isoprene emissions (Is) from neotropical species Inga edulis Mart. as a function of light and temperature under ambient (450 µmol m−2 s−1) and CO2-free (0 µmol m−2 s−1) atmosphere. Is under CO2-free atmosphere showed light-dependent emission patterns similar to those observed under ambient CO2, but with lower light saturation point. Leaves treated with the photosynthesis inhibitor DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) failed to produce detectable Is in normal light under a CO2-free atmosphere. While strong temperature-dependent Is were observed under CO2-free atmosphere in the light, dark conditions failed to produce detectable Is even at the highest temperatures studied (40 °C). Treatment of leaves with 13C-labeled sodium bicarbonate under CO2-free atmosphere resulted in Is with over 50% containing at least one 13C atom. Is under CO2-free atmosphere and standard conditions of light and leaf temperature represented 19% ± 7% of emissions under ambient CO2. The results show that the reassimilation of leaf internal CO2 contributes to Is in the neotropical species I. edulis. Through the consumption of excess photosynthetic energy, our results support a role of isoprene biosynthesis, together with photorespiration, as a key tolerance mechanism against high temperature and high light in the tropics.
Highlights
Isoprene (2-methyl-1,3-butadiene, C5 H8 ) is a reactive hydrocarbon gas emitted in large amounts to the atmosphere by many plants [1,2]
We further investigated the potential for the reassimilation of CO2 release by internal decarboxylation processes using an inhibitor of photosynthesis under CO2 -free reference air
Most studies have focused on stored carbon sources including carbohydrates and their metabolites as potentially important alternative carbon sources and few studies are made with tropical species
Summary
Isoprene (2-methyl-1,3-butadiene, C5 H8 ) is a reactive hydrocarbon gas emitted in large amounts to the atmosphere by many plants [1,2]. Forests 2019, 10, 472 important role in atmospheric chemistry involving air quality and climate [5]. Despite great advances in our knowledge on the roles of plant Is on atmospheric chemistry, much less is known about the physiological roles that isoprene plays in plants [9,10,11]. The emerging view is that isoprene production can protect photosynthesis during abiotic stress through mechanisms including excess photosynthetic energy consumption, physical stability of biological membranes, and direct roles as an antioxidant through reactions with reactive oxygen species that accumulate under stress conditions [12,13]. Recent work has noted that protection of photosynthesis through isoprene via the physical stabilization of membranes may not be possible and that the mechanisms of protection from oxidative stress are still unclear [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
