Reassimilation of Leaf Internal CO₂ Contributes to Isoprene Emission in the Neotropical Species Inga edulis Mart.

Journal Article · 30 May 2019 · Forests

DOI: https://doi.org/10.3390/f10060472 · OSTI ID:1560599

Garcia, Sabrina  ^[1]; Jardine, Kolby  ^[2]; Souza, Vinicius  ^[3]; Souza, Rodrigo ^[4]; Duvoisin Junior, Sergio ^[3]; Gonçalves, José  ^[1]

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1. National Inst. for Amazonian Research (INPA), Avenida André Araújo, Amazonas (Brazil)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Science Division
3. State Univ. of Amazonas, Avenida Darcy Vargas, Amazonas (Brazil). Faculty of Chemical Engineering
4. State Univ. of Amazonas, Amazonas (Brazil). Meteorology Dept.

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.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1560599
• Journal Information: Forests, Vol. 10, Issue 6; ISSN 1999-4907
• Publisher: MDPICopyright Statement
• Country of Publication: United States
• Language: English