Cross-Talk between Physiological and Metabolic Adjustments Adopted by Quercus cerris to Mitigate the Effects of Severe Drought and Realistic Future Ozone Concentrations

Abstract

Global climate change represents a moving target for plant acclimation and/or adaptation, especially in the Mediterranean basin. In this study, the interactions of severe drought (20% of the effective daily evapotranspiration) and O 3 fumigation (80 ppb, 5 h day −1 , for 28 consecutive days) on (i) photosynthetic performance, (ii) cell membrane stability, (iii) hydric relations, (iv) accumulation of compatible solutes, and (v) lipophilic antioxidant compounds were investigated in young Quercus cerris plants. In addition to the typical drought-induced stomatal closure, imposition of water withholding dramatically influenced the profile of stress-associated metabolites, i.e., abscisic acid (ABA), proline, and lipophilic antioxidants. However, plants were not able to delay or prevent the negative effects of water deficit, the greatest impacting factor in this study. This translated into a steep decline of photosynthetic efficiency, leaf hydration, and membrane fluidity and permeability. When water stress was coupled with O 3 , plants orchestrated cross-talk among ABA, proline, and sugar in fully-expanded mature leaves, partially leading to a premature senescence.

Species-Level Differences in Osmoprotectants and Antioxidants Contribute to Stress Tolerance of Quercus robur L., and Q. cerris L. Seedlings under Water Deficit and High Temperatures

“…Our findings show that Turkey oak (Q. cerris) and pedunculate oak (Q. robur) seedlings responded to the applied soil water deficit and high air temperature conditions by (Figure 9): (1) increasing differently the levels of several components of their osmoregulation and antioxidative defense system depending on the species and the nature of the stress; (2) upregulating the synthesis of the newly-explored metabolite dimethylsulphoniopropionate (DMSP); (3) trading-off between multifaceted components of the protection system; and (4) modulating the synthesis of stress-related (ABA) and developmental-related (IAA) hormones. The occurrence of oxidative stress in leaves of both species under both soil water deficit and high air temperature conditions (i.e., increased membrane lipid peroxidation), is consistent with similar results in Quercus [58], including Q. cerris and Q. robur (Table 1) [42,59,60]. However, the low level of lipid peroxidation, together with the increasing response pattern of mostly biochemical parameters to both stress conditions, suggest an acclimation to oxidative stress for the examined species [61].…”

Antioxidative responses of three oak species under ozone and water stress conditions

“…Under drought, plants usually suffer from the impairment of many physiological and biochemical processes, such as (i) alteration of photosynthetic performance, (ii) cell dehydration, (iii) high production of reaction oxygen species (ROS) and, finally, (iv) early senescence and/or leaf necrosis (Chaves et al, 2003). Similar effects have also been attributed to O3 (Cotrozzi et al, 2017a;Jolivet et al, 2016). A combination of drought and O3 can induce responses considerably different from those observed when each stressor is applied independently (Bohler et al, 2015).…”

Combined effects of ozone and drought stress on the emission of biogenic volatile organic compounds from <i>Quercus robur</i> L.

“…Besides increasing temperature and more severe droughts, future climate scenarios predict increasing ozone concentrations (Bowen, 1926;Kangasjärvi et al, 1994;Hollaway et al, 2012). Long-term elevated tropospheric ozone concentration affects BVOC emissions (Peñuelas et al, 1999) and induces alterations in photosynthetic performance, increasing the production of reactive oxygen species (ROSs) (Cotrozzi et al, 2017;Jolivet et al, 2016).…”