Abstract
Drought is one of the main constraints determining forest species growth, survival and productivity, and therefore one of the main limitations for reforestation or afforestation. The aim of this study is to characterize the drought response at the physiological and molecular level of different Pinus halepensis (common name Aleppo pine) seed sources, previously characterized in field trials as drought-sensitive or drought-tolerant. This approach aims to identify different traits capable of predicting the ability of formerly uncharacterized seedlings to cope with drought stress. Gas-exchange, water potential, photosynthetic pigments, soluble sugars, free amino acids, glutathione and proteomic analyses were carried out on control and drought-stressed seedlings in greenhouse conditions. Gas-exchange determinations were also assessed in field-planted seedlings in order to validate the greenhouse experimental conditions. Drought-tolerant seed sources presented higher values of photosynthetic rates, water use efficiency, photosynthetic pigments and soluble carbohydrates concentrations. We observed the same pattern of variation of photosynthesis rate and maximal efficiency of PSII in field. Interestingly drought-tolerant seed sources exhibited increased levels of glutathione, methionine and cysteine. The proteomic profile of drought tolerant seedlings identified two heat shock proteins and an enzyme related to methionine biosynthesis that were not present in drought sensitive seedlings, pointing to the synthesis of sulfur amino acids as a limiting factor for drought tolerance in Pinus halepensis. Our results established physiological and molecular traits useful as distinctive markers to predict drought tolerance in Pinus halepensis provenances that could be reliably used in reforestation programs in drought prone areas.
Highlights
In the context of climate change, the fate of many forest ecosystems depends on their adaptation to such changes (Chen and Jiang, 2010)
Only net photosynthesis (Pn) was statistically significant between tolerant and sensitive seed sources when analyzed globally but no differences can be found among means values for each seed source
Our results indicate that the alternative biosynthesis of Met, together with the synthesis of GSH are associated to drought tolerance in Pinus halepensis
Summary
In the context of climate change, the fate of many forest ecosystems depends on their adaptation to such changes (Chen and Jiang, 2010). Interspecific variation in key functional traits along environmental gradients can explain adaptive patterns related to environmental cues (Sánchez-Gómez et al, 2010) This variation can happen at an intraspecific level, which would explain adaptive patterns among different populations throughout the geographical range of individual species (Taïbi et al, 2014, 2015). For reforestation and ecological restoration, the common strategy was based on the use of local genotypes or genotypes previously represented. One defect of this approach is that it does not consider forest migration and changes in environmental factors, which may lead to failure in reforestation programs and to an unnecessary waste of resources and time (Williams and Dumroese, 2013)
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