A coastal and an interior Douglas fir provenance exhibit different metabolic strategies to deal with drought stress

Abstract

Drought is a major environmental stress affecting growth and vitality of forest ecosystems. In the present study, foliar nitrogen (N) and carbon (C) metabolism of two Douglas fir (Pseudotsuga menziesii) provenances with assumed different drought tolerance were investigated. We worked with 1-year-old seedlings of the interior provenance Fehr Lake (FEHR) originating from a dry environment and the coastal provenance Snoqualmie (SNO) from a more humid origin. Total C and N, structural N and the concentrations of soluble protein, total amino acids (TAAs) and individual amino acids as well as the relative abundance of polar, low-molecular-weight metabolites including antioxidants were determined in current-year needles exposed either to 42 days of drought or to 42 days drought plus 14 days of rewatering. The seedlings reacted in a provenance-specific manner to drought stress. Coastal provenance SNO showed considerably increased contents of TAAs, which were caused by increased abundance of the quantitatively most important amino acids arginine, ornithine and lysine. Additionally, the polyamine putrescine accumulated exclusively in drought-stressed trees of this provenance. In contrast, the interior provenance FEHR showed the opposite response, i.e., drastically reduced concentrations of these amino acids. However, FEHR showed considerably increased contents of pyruvate-derived and aromatic amino acids, and also higher drought-induced levels of the antioxidants ascorbate and α-tocopherol. In response to drought, both provenances produced large amounts of carbohydrates, such as glucose and fructose, most likely as osmolytes that can readily be metabolized for protection against osmotic stress. We conclude that FEHR and SNO cope with drought stress in a provenance-specific manner: the coastal provenance SNO was mainly synthesizing N-based osmolytes, a reaction not observed in the interior provenance FEHR; instead, the latter increased the levels of scavengers of reactive oxygen species. Our results underline the importance of provenance-specific reactions to abiotic stress.

Waterlogging Tolerance of 57 Plant Species Grown Hydroponically

“…Differences in abiotic stress tolerance among provenances of the same species from different climatic zones have been observed (Carsjens et al, 2014;Du et al, 2016;Yildiz et al, 2014), which is contrary to our second hypothesis that phenotypic divergence would not occur among provenances of the same species under waterlogging stress. This variability may be caused by differences among habitats and the duration of provenance separation.…”

Foliar nitrogen metabolism of adult Douglas-fir trees is affected by soil water availability and varies little among provenances

“…Besides variation in N pools as a consequence of genotypic differentiation or genotypic variation in plasticity, N metabolism of trees is also affected by acclimatization to variation in environmental conditions [ 35 , 36 ]. Water shortage and elevated temperature exert strong effects on tree N metabolism [ 37 , 38 ].…”

“…Under drought and / or heat, foliar total amino acid contents, particularly amino acids from the glutamate family (e.g. glutamate, arginine), increased in deciduous [ 39 , 40 ] and conifer species [ 35 , 41 – 43 ]. Accumulation of arginine in needles was regarded as a general response of conifers to stresses causing a reduction in growth [ 26 ].…”

A molecular approach to drought‐induced reduction in leaf CO2 exchange in drought‐resistant Quercus ilex

“…Few studies have addressed leaf responses to soil drought stress in tree species by combining molecular (e.g. metabolomics and transcriptomics) and physiological approaches (Jansen et al , Du et al ), and even fewer addressing long drought periods in non‐commercial tree species of slow growth and high drought resistance (Valero‐Galván et al , Rivas‐Ubach et al ). To shed light on the mechanisms underpinning reduced rates of photosynthesis and respiration under drought, in our study, leaf gas exchange rates were analyzed together with gene expression and gas chromatography time‐of‐flight mass spectrometry (GC‐TOF‐MS) primary metabolite profiling in Quercus ilex L. seedlings exposed to increasing levels of drought severity.…”