The impacts of droughts on species and ecosystems are becoming stronger and more critical to understand, and model species Arabidopsis thaliana provides an excellent platform to elucidate potential mechanisms and trade-offs in drought responses. The leaf osmotic potential at turgor loss point (πTLP) is a key determinant and predictor of drought tolerance, as a measure of the ability of plants to maintain photosynthetic function as soil moisture declines. Across species and biomes, more negative values for πTLP are associated with greater climatic aridity. However, no studies have tested this pattern across genotypes of a single species spanning a large geographic range. Further, previous theory has hypothesized a trade-off between drought tolerance and relative growth rate, but conflicting evidence has been presented across species, and little work has focused on this trade-off within a model system. The aim of this study was to test Arabidopsis ecotypes native to a range of climates for potential trade-offs between growth and drought tolerance traits, and to determine how these traits are associated with origin climate.
Results/Conclusions:
We analyzed growth and drought tolerance traits in a common garden experiment for eight Arabidopsis ecotypes representing a range of native environments and genetic backgrounds, selected from a larger group of 1001 genotypes for which genomic information is available. We tested for correlations among growth and drought tolerance traits, and for relationships between these traits and climate variables. There was a strong relationship between the πTLP and several climate factors: the πTLP was more negative with greater aridity and lower annual precipitation and with greater potential evapo-transpiration in the native range. By contrast, we found no relationship between relative growth rate (RGR) and native climate variables, or with πTLP. Our results support the hypothesis that the πTLP varies consistently with native climate across Arabidopsis ecotypes, confirming the utility and importance of the πTLP as a predictor of plant performance at many scales. Our results also show that relative growth rate is independent from πTLP, consistent with a lack of a trade-off between growth and drought tolerance across genotypes of a given species.