Variation in the performance and thermostability of photosystem II in European beech (Fagus sylvatica L.) provenances is influenced more by acclimation than by adaptation

Abstract

The assisted migration of resistant seeds and seedlings may be a key to mitigating the effects of climate change on the productivity and composition of forest ecosystems. These efforts require an understanding of the intraspecific variability in the response of trees to extreme weather events such as heat waves. In this study, we assessed the geographical patterns of photosystem II (PSII) performance and thermostability in European beech (Fagus sylvatica L.) and whether intraspecific differences are associated with climate of origin. Two provenance trials with starkly contrasting climates were used for this study. Leaves were sampled both before and after natural heat stress exposure. Rapid chlorophyll fluorescence kinetics was used to evaluate PSII performance and PSII thermostability after simulated heat stress. The performance of PSII at 30 °C, which is still considered a non-damaging temperature, was generally slightly better at the warmer location than at the colder location. The populations originating closer to the Slovenian refugium, as well as those growing closer to their site of origin, showed better performance of PSII but not greater thermostability. The effect of simulated heat stress was much stronger in the colder plots compared to the warmer plots, but only for previously stressed trees. Likewise, we found indicators of geographical patterns of thermotolerance as well as relationships between thermotolerance and climate of origin mostly for trees exposed to natural heat. While the origin of provenances partly explained the variation among provenances, acclimation driven by climate played a major role in the response to heat stress. In beech, PSII seems to have a potential for coping with high temperature.

Priming Maritime Pine Megagametophytes during Somatic Embryogenesis Improved Plant Adaptation to Heat Stress

“…Thylakoid membranes of chloroplasts are especially sensitive to an increase in fluidity by heat, which can also cause damage to PSII through protein denaturation. Maximum quantum yield of PSII (ΦPSII = Fv/Fm) in native Mediterranean species, including forest trees, decreased to 50% between 41 and 45 • C as compared to 25 • C [16,17,59]; this also holds true in species of agri-food interest such as tomato [69]. Previously, Adams and Demmig-Adams [70] reported that temperature variation (increase or decrease) negatively affects PSII efficiency in conifers, and induced changes in chlorophyll content, which is indicative of an excess of energy causing damage to the photosynthetic apparatus.…”

“…Previous studies on the adaptation thermotolerance in several forest species demonstrated that photosynthetic activity is one of the vital processes most affected by the increase of temperature [16,17]. In radiata pine thermotolerance acquisition was also related to hormone profile, photosynthetic pigments and carbohydrate contents [18,19].…”

Stomatal and Leaf Morphology Response of European Beech (Fagus sylvatica L.) Provenances Transferred to Contrasting Climatic Conditions

“…The effect of environmental change on a provenance planted at a given location can be expressed as the difference between the ecological characteristics of the trial plot and the site of provenance origin, called the ecodistance [22]. Moreover, if we study the performance of populations in different provenance trial plots and the differences between plots are greater than within, we expect that the differences between phenotypes are driven more by acclimation to current environmental conditions than by local adaptation [23,24]. Stomatal and leaf morphological traits such as stomatal density, potential conductance index and specific leaf area affect stomatal conductance and transpiration (functional traits) which in return influence performance, growth and survival [13,19].…”

Intra-annual stem size variations converge across marginal populations of European beech

“…However, the majority of them focus on the southern, western, and/or northern margins of beech distribution range. Only a few of them have included populations from the northern or eastern distribution range and, when included, only one marginal population was analyzed, thus preventing to assess the phenotypic variability for representative groups (Kolář et al 2017;Kurjak et al 2018;Weigel et al 2018;Rose et al 2009). Our study covered northern part of the south-eastern boundary of the biogeographic range of beech, revealing that intra-population variability oversteps inter-population variability of seasonal SCV, regardless of dry or wet growing seasons (Table 1).…”