The use of branch enclosures to assess direct and indirect effects of elevated CO2 on photosynthesis, respiration and isoprene emission of Populus alba leaves

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

“…In these studies, photosynthetic capacity (light-saturated net assimilation rate standardized to a common C i , or Farquhar et al (1980) model parameters V cmax and J max ) was not affected by ele- Fig. 5. vated [CO 2 ] or was even "upregulated" in elevated-[CO 2 ]-grown plants (our study, Darbah et al, 2010;Rapparini et al, 2004;Staudt et al, 2001;Loreto et al, 2001a;Calfapietra et al, 2007Calfapietra et al, , 2008Sharkey et al, 1991;Brilli et al, 2007b). Data were fitted by linear regressions: r 2 = 0.75, P < 0.001 for A380; r 2 = 0.11, P > 0.3 for A780; r 2 = 0.71, P < 0.001 for E380 and r 2 = 0.59, P < 0.01 for E780.…”

“…Symbols as in Fig. 5. vated [CO 2 ] or was even "upregulated" in elevated-[CO 2 ]-grown plants (our study, Darbah et al, 2010;Rapparini et al, 2004;Staudt et al, 2001;Loreto et al, 2001a;Calfapietra et al, 2007Calfapietra et al, , 2008Sharkey et al, 1991;Brilli et al, 2007b). In contrast, in all studies reporting reduced isoprene emissions under elevated [CO 2 ], there was also downregulation in photosynthetic capacity (Darbah et al, 2010 one aspen clone); (Possell et al, 2004;Scholefield et al, 2004;Monson et al, 2007;Possell & Hewitt, 2009Velikova et al, 2009;Wilkinson et al, 2009).…”

“…Some studies demonstrate reduced emission capacity in elevated-CO 2 -grown plants, including Acacia nigrescens (Possell & Hewitt, 2011), Liquidambar styraciflua Wilkinson et al, 2009), Populus tremuloides (Darbah et al, 2010 one clone), (Sharkey et al, 1991), Eucalyptus globulus, P. tremuloides and P. deltoides , Phragmites australis (Scholefield et al, 2004), and Platanus orientalis (Velikova et al, 2009). However, other studies have either found no significant change, including P. tremuloides (Darbah et al, 2010 another aspen clone), (Calfapietra et al, , 2008, P. x canescens (Trowbridge et al, 2012), Populus alba (Loreto et al, 2001a(Loreto et al, , 2007Brilli et al, 2007b), Quercus chapmanii (Buckley, 2001) and Quercus pubescens (Rapparini et al, 2004), or even increased emissions in Gingko biloba (Li et al, 2009), Q. pubescens (Tognetti et al, 1998) and Q. rubra (Sharkey et al, 1991). This large study-to-study variability is currently not understood, but suggests that acclimation of isoprene emission capacity to elevated [CO 2 ] depends both on changes in isoprene synthase activity and alterations in DMADP pool size that may both increase or decrease under elevated [CO 2 ] or the integrated response may be dominated by one of them.…”

Isoprene is more affected by climate drivers than monoterpenes: A meta‐analytic review on plant isoprenoid emissions

“…Indeed, reduction of Ci stimulates isoprene emission (Guidolotti et al, ) by an effect opposite to the inhibition caused by elevated CO 2 . As isoprenoid formation depends on metabolites, which are primarily formed by photosynthesis, a decrease in emissions is expected to occur when a severe drought stress inhibits primary metabolism (Brilli, Tricoli, Fares, Centritto, & Loreto, ; Fortunati et al, ; Ormeño et al, ; Wu et al, ), and this may appear even days after stomatal closure and photosynthesis down‐regulation had begun (Beckett et al, ; Tattini et al, ). Clearly, most of the meta‐analysed studies fell into this group of responses, as also suggested by the large average reduction of soil water content in the examined papers.…”