Drought and air warming affect the species-specific levels of stress-related foliar metabolites of three oak species on acidic and calcareous soil

Abstract

Climate change as projected for Central Europe will lead to prolonged periods of summer drought and enhanced air temperature. Thus, forest management practices are required to take into account how species performance is adapted to cope with these climate changes. Oak trees may play a major role in future forests because of their relative drought-tolerance compared with other species like beech. Therefore, this study investigated the stress responses (i.e., anti-oxidants, free amino acids) in the leaves of three widely distributed oak species in Central Europe (i.e., Quercus robur L., Q. petraea [Matt.] Libel., Q. pubescens Willd.) to drought, air warming and the combination of drought plus air warming under controlled conditions after periods of spring drought, a short rewetting and summer drought. We quantified foliar levels of thiols, ascorbate, and free amino compounds in Q robur, Q. petraea and Q. pubescens. Our study showed that oak saplings had increased levels of γ-glutamylcysteine and total glutathione and proline with drought and air warming. Foliar ascorbate, glutathione disulfide and dehydroascorbic acid levels were not affected. The comparison of stress responses to drought and/or air warming between the three species showed higher foliar thiol levels in Q. robur and Q. pubescens compared with Q. petraea. For total and reduced ascorbic acid and γ-aminobutyric acid, the highest levels were found in Q. robur. In conclusion, our study showed that foliar anti-oxidant and free amino acid levels were significantly affected by drought plus air warming; however, this effect was species-dependent with the drought-tolerant species of Q. pubescens having the highest reactive oxygen species scavenging capacity among three tested oak species. Furthermore, stress responses as shown by increased levels of foliar anti-oxidants and free amino acids differ between calcareous and acidic soil indicating that the capacities of anti-oxidative defense and osmotic stress adjustment developed better on calcareous compared with acidic soil; however, this effect was metabolite- as well as species-specific.

Prey-Mediated Effects of Drought on the Consumption Rates of Coccinellid Predators of Elatobium abietinum

“…The effects of drought on plants themselves range from effects at a cellular level [55] and on plant chemistry [56,57,58,59], through to changes to plant structure [55,60] and growth [60,61,62]. Furthermore, by modifying the nutrient uptake by a plant [63], drought also has the potential to affect phloem sap quality for phloem-feeding insects such as aphids, much as turgor pressure affects availability of the sap to the herbivores.…”

Solar UV Upregulates Photoprotection but Slows Photosynthesis in Subalpine Australian Plants

“…Thiols were extracted and their redox status of leaves was determined as per Hu et al (2013). Thiols were extracted from 30 mg homogenized frozen leaf tissue in pre-cooled 750 µL 0.1 M HCl with 50 mg PVPP.…”

“…For oxidized thiols, 20 μL of 20 mM N-ethylamide (NEM) was added to tube for 15 min prior to reduction with DTT, to block reduced thiols (Hu et al, 2013). Tubes were incubated for 1 h at room temperature before reduction was terminated with 20 μL of 30 mM monobromobimane (mBBr).…”

Nonlinear tree growth dynamics predict resilience to disturbance

“…For example, investigators have elucidated distinct physiological responses of different cooccurring tree genera (Breshears et al 2005, 2009, Eilmann and Rigling 2012, Mitchell et al 2013) and co-occurring oak species (Hu et al 2013, Renninger et al 2014 to drought. Such studies help investigators predict which tree species may be relatively resilient to this type of disturbance.…”

“…Testing this hypothesis cannot discern the mechanism driving tree survival or susceptibility to disturbance. However, unlike more mechanistic studies exploring trees' physiological response to a particular disturbance type (Breshears et al 2005, 2009, Eilmann and Rigling 2012, Hu et al 2013, Mitchell et al 2013, Renninger et al 2014), our approach is applicable to a multitude of disturbance types. We use the results of our work to begin to disentangle the mystery of why some trees appear susceptible to v www.esajournals.org disturbance, while conspecifics with apparently similar access to resources and co-dominance status in the canopy succumb.…”