Leaf isoprene and monoterpene emission distribution across hyperdominant tree genera in the Amazon basin. (July 2020)

• Record Type: Journal Article
• Authors: Jardine, Kolby J.; Zorzanelli, Raquel F.; Gimenez, Bruno O.; Oliveira Piva, Luani Rosa de; Teixeira, Andrea; Fontes, Clarissa G.; Robles, Emily; Higuchi, Niro; Chambers, Jeffrey Q.; Martin, Scot T.
• Is Part Of: Phytochemistry. Volume 175(2020)
• Publication Date: 2020-07
• Subjects: Protium -- Licania -- Inga -- And Eschweilera, isoprene and monoterpene emissions in the amazon rainforest -- Isoprene synthase -- Mycene/ocimene synthase; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2020.112366
• Languages: English
• ISSNs: 0031-9422

Abstract

Abstract: Tropical forests are acknowledged to be the largest global source of isoprene (C5 H8 ) and monoterpenes (C10 H16 ) emissions, with current synthesis studies suggesting few tropical species emit isoprenoids (20–38%) and do so with highly variable emission capacities, including within the same genera. This apparent lack of a clear phylogenetic thread has created difficulties both in linking isoprenoid function with evolution and for the development of accurate biosphere-atmosphere models. Here, we present a systematic emission study of "hyperdominant" tree species in the Amazon Basin. Across 162 individuals, distributed among 25 botanical families and 113 species, isoprenoid emissions were widespread among both early and late successional species (isoprene: 61.9% of the species; monoterpenes: 15.0%; both isoprene and monoterpenes: 9.7%). The hyperdominant species (69) across the top five most abundant genera, which make up about 50% of all individuals in the Basin, had a similar abundance of isoprenoid emitters (isoprene: 63.8%; monoterpenes: 17.4%; both 11.6%). Among the abundant genera, only Pouteria had a low frequency of isoprene emitting species (15.8% of 19 species). In contrast, Protium, Licania, Inga, and Eschweilera were rich in isoprene emitting species (83.3% of 12 species, 61.1% of 18 species, 100% of 8 species, and 100% of 12 species, respectively). Light response curves of individuals in each of the five genera showed light-dependent, photosynthesis-linked emission rates of isoprene and monoterpenes. Importantly, in every genus, we observed species with light-dependent isoprene emissions together with monoterpenes including β-ocimene. These observations support the emerging view of the evolution of isoprene synthases from β-ocimene synthases. Our results have important implications for understanding isoprenoid function-evolution relationships and the development of more accurate Earth System Models. Graphical abstract: Graphical illustration of the biochemical, ecological, and atmospheric roles of volatile isoprenoids (isoprene and monoterpenes) within plants, ecosystems, and the atmosphere. Volatile isoprenoids protect photosynthesis during abiotic stress, are involved in multi-trophic interactions within ecosystems, and following atmospheric oxidation, impact climate through influences over secondary organic aerosol (SOA) and cloud condensation nuclei (CCN) lifecycles in the troposphere. Image 1 Highlights: A systematic study across five abundant tree genera in the Amazon found widespread occurrence of leaf isoprenoid emissions. Isoprene and β-ocimene co-emissions support the emerging view of isoprene synthase evolution from mycene/ocimene synthases. The finding of widespread isoprenoid emissions among abundant genera may aid development of mechanistic Earth System Models.