Enhanced isoprene emission capacity and altered light responsiveness in aspen grown under elevated atmospheric CO₂ concentration

Abstract

Controversial evidence of CO2‐responsiveness of isoprene emission has been reported in the literature with the response ranging from inhibition to enhancement, but the reasons for such differences are not understood. We studied isoprene emission characteristics of hybrid aspen (Populus tremula x P. tremuloides) grown under ambient (380 μmol mol−1) and elevated (780 μmol mol−1) [CO2] to test the hypothesis that growth [CO2] effects on isoprene emission are driven by modifications in substrate pool size, reflecting altered light use efficiency for isoprene synthesis. A novel in vivo method for estimation of the pool size of the immediate isoprene precursor, dimethylallyldiphosphate (DMADP) and the activity of isoprene synthase was used. Growth at elevated [CO2] resulted in greater leaf thickness, more advanced development of mesophyll and moderately increased photosynthetic capacity due to morphological “upregulation”, but isoprene emission rate under growth light and temperature was not significantly different among ambient‐ and elevated‐[CO2]‐grown plants independent of whether measured at 380 μmol mol−1 or 780 μmol mol−1 CO2. However, DMADP pool size was significantly less in elevated‐[CO2]‐grown plants, but this was compensated by increased isoprene synthase activity. Analysis of CO2 and light response curves of isoprene emission demonstrated that the [CO2] for maximum isoprene emission was shifted to lower [CO2] in elevated‐[CO2]‐grown plants. The light‐saturated isoprene emission rate (Imax,Q) was greater, but the quantum efficiency at given Imax,Q was less in elevated‐[CO2]‐grown plants, especially at higher CO2 measurement concentration, reflecting stronger DMADP limitation at lower light and higher [CO2]. These results collectively demonstrate important shifts in light and CO2‐responsiveness of isoprene emission in elevated‐[CO2]‐acclimated plants that need consideration in modeling isoprene emissions in future climates.

Advances in understanding CO2 responsive plant metabolomes in the era of climate change

“…Isoprene emissions of hybrid aspen (P. tremula 9 P. tremuloides) grown under ambient or elevated (780 ppm) CO 2 indicated that the isoprene emission rates remained unaltered, although the pool of the isoprene precursor DMAPP was significantly smaller in plants grown under elevated CO 2 (Sun et al 2012). In addition, isoprene emission and respiration rates of the leaves of white poplar (P. alba L.) grown in a free-air carbon dioxide enrichment (FACE) facility were not affected by elevated CO 2 .…”

Temperature responses of the Rubisco maximum carboxylase activity across domains of life: phylogenetic signals, trade-offs, and importance for carbon gain

“…In general, photosynthesis models are applied assuming that the temperature responses of k c cat (or V cmax ) are invariable across species (Niinemets and Tenhunen 1997;Bernacchi et al 2001;Sharkey et al 2007;Díaz-Espejo 2013;Rogers 2014). Actually, many contemporary studies, irrespective of the species considered, use the temperature functions provided for tobacco (Bernacchi et al 2001(Bernacchi et al , 2003 to model photosynthesis in a range of environmental conditions (e.g., Yamori and von Caemmerer 2009;Galmés et al 2011;Bermúdez et al 2012), while many others use spinach (Jordan and Ogren 1984) Rubisco kinetics (e.g., Harley et al 1992;Niinemets et al 2009;Sun et al 2012). However, some evidence already exists suggesting that the temperature response of V cmax might vary among species (Zhu et al 1998;Hikosaka et al 2006;Archontoulis et al 2012;Walker et al 2013).…”

Metabolic Flux Analysis of Plastidic Isoprenoid Biosynthesis in Poplar Leaves Emitting and Nonemitting Isoprene

“…Isoprene emission rates depend mainly on the availability of photosynthetic intermediates, the lightdependent delivery of energy, and redox equivalents as well as the amount of ISPS (for review, see Sharkey and Yeh, 2001;Sharkey et al, 2008); all these parameters are similarly affected by environmental constraints , with the exception of CO 2 concentrations (Rosenstiel et al, 2003;Sun et al, 2012;Way et al, 2013). Changes in light intensity and temperature rapidly affect the pools of MEcDP and plastidic DMADP in IE leaves, which is also reflected in the changes of isoprene emission (Rodríguez-Concepción, 2006;Rasulov et al, 2010;Mongélard et al, 2011).…”