Facing the Future: Effects of Short-Term Climate Extremes on Isoprene-Emitting and Nonemitting Poplar

Abstract

(H.R.); 0000-0002-9825-867X (J.-P.S.).Isoprene emissions from poplar (Populus spp.) plantations can influence atmospheric chemistry and regional climate. These emissions respond strongly to temperature, [CO 2 ], and drought, but the superimposed effect of these three climate change factors are, for the most part, unknown. Performing predicted climate change scenario simulations (periodic and chronic heat and drought spells [HDSs] applied under elevated [CO 2 ]), we analyzed volatile organic compound emissions, photosynthetic performance, leaf growth, and overall carbon (C) gain of poplar genotypes emitting (IE) and nonemitting (NE) isoprene. We aimed (1) to evaluate the proposed beneficial effect of isoprene emission on plant stress mitigation and recovery capacity and (2) to estimate the cumulative net C gain under the projected future climate. During HDSs, the chloroplastidic electron transport rate of NE plants became impaired, while IE plants maintained high values similar to unstressed controls. During recovery from HDS episodes, IE plants reached higher daily net CO 2 assimilation rates compared with NE genotypes. Irrespective of the genotype, plants undergoing chronic HDSs showed the lowest cumulative C gain. Under control conditions simulating ambient [CO 2 ], the C gain was lower in the IE plants than in the NE plants. In summary, the data on the overall C gain and plant growth suggest that the beneficial function of isoprene emission in poplar might be of minor importance to mitigate predicted short-term climate extremes under elevated [CO 2 ]. Moreover, we demonstrate that an analysis of the canopy-scale dynamics of isoprene emission and photosynthetic performance under multiple stresses is essential to understand the overall performance under proposed future conditions. Climate change will lead to an increase in global temperatures of at least 2°C in the near future (IPCC, 2014). There is at present substantial evidence that this climate change is leading to an increase in the frequency and intensity of extreme events such as heat and drought waves (Feyen and Dankers, 2009;Fischer and Schär, 2010;Perkins et al., 2012;Thornton et al., 2014), creating a sequence of recurring stress and recovery cycles for plants. Coumou and Rahmstorf (2012) showed that, in the last 15 years, five extreme heat wave events have occurred worldwide, four of which were observed also in Europe. Interactions between heat and drought under predicted elevated [CO 2 ] (IPCC, 2014) generate complex, often nonadditive physiological responses. Such effects cannot be predicted by singlefactor analyses and highlight the importance of carrying out controlled, multistress scenarios to investigate plant performance under future climate conditions (Clausen et al., 2011; Alemayehu et al., 2014).Photosynthesis, respiration, and photorespiration are the three dominating processes determining carbon (C) exchange and C metabolism in plants (Bauwe et al., 2010;Mahecha et al., 2010). In addition, the emission of biogenic volatile organic c...

Drought stress and carbon assimilation in a warming climate: Reversible and irreversible impacts

“…The accumulation and compartmentation of some metabolites (expecially of ROS scavengers and of compatible solutes such as proline, betain or glycinebetaine which are also important for osmoregulation) help to protect cells from damages caused by heat or drought and to maintain basic cellular functions (Hormaetxe et al, 2007;Wang et al, 2010;Albert et al, 2012;Hu et al, 2013;Wujeska et al, 2013: AbdElgawad et al, 2015Grant et al, 2015). Such protective effects were recently reported in detail for phenolic compounds (Farfan-Vignolo and Asard, 2012;Wegener et al, 2015), α-tocopherol (MunneBosch and Alegre, 2000; Farfan-Vignolo and Asard, 2012) and for isoprene production/emission (Velikova et al, 2005 ;Velikova, 2008;Centritto et al, 2014 ;Seco et al, 2015 ;Vanzo et al, 2015). Advantages of drought acclimation for improved plant performance were reported by Selote et al (2004).…”

Isoprene emission and photosynthesis during heatwaves and drought in black locust

“…In addition, within the suit of measured volatiles we found no indication for other compounds, which should co-occur with such C5-volatiles (e.g., C6 leaf alcohols or acetaldehyde). In a similar study the absence of those compounds during a heat-drought wave was attributed to natural drought progression not being comparable to fast drying after artificial cutting (Vanzo et al, 2015).…”

“…After periods of drought stress, a quick recovery of isoprene emissions seems to emerge as a common feature that has also been observed in previous studies (Sharkey and Loreto, 1993;Pegoraro et al, 2004b;Velikova and Loreto, 2005;Brilli et al, 2013) and may help isoprene emitting plants to cope with abrupt and repeated temperature changes as commonly observed under natural conditions. However, studies on isoprene dynamics following stress release are scarce and there is to our knowledge only one study that considers dynamics of isoprene emissions during and following prolonged combined heatdrought stress (Vanzo et al, 2015). Vanzo et al (2015) found that isoprene-emitting poplars recovered rapidly from stress and even increased photosynthesis during recovery in contrast to nonisoprene-emitting trees, which showed weaker recovery of photosynthesis.…”

“…However, studies on isoprene dynamics following stress release are scarce and there is to our knowledge only one study that considers dynamics of isoprene emissions during and following prolonged combined heatdrought stress (Vanzo et al, 2015). Vanzo et al (2015) found that isoprene-emitting poplars recovered rapidly from stress and even increased photosynthesis during recovery in contrast to nonisoprene-emitting trees, which showed weaker recovery of photosynthesis. Net photosynthesis in our study recovered quickly, too.…”

“…Drought periods often coincide with high temperatures (Boeck and Verbeeck, 2011). While some efforts have been made to quantify isoprene emissions in presence of single stress factors like high temperature (Sharkey and Loreto, 1993;Singsaas and Sharkey, 2000) or soil water deficit (Pegoraro et al, 2004b;Brilli et al, 2007Brilli et al, , 2013Ryan et al, 2014), there is up to now only one study that has studied the effects of combined prolonged heat and drought on trees (Vanzo et al, 2015). Additionally, most stress-response studies have been based on fixed environmental conditions, for instance the application of discrete temperature steps, and stress exposure was often limited to short time periods and only applied to specific plant tissues such as leaves.…”