A hypothesized trade-off between growth and drought tolerance has figured prominently in plant ecological theory. However, experimental and observational evidence across species has been controversial, and few studies have focused on ecotypes within given species. Plants can potentially adapt to drought in multiple ways, from surviving and maintaining function through drought to, alternatively, avoiding the drought by growing rapidly when conditions are favorable. We tested for potential trade-offs between growth and drought tolerance traits for ecotypes of model species Arabidopsis thaliana native to a wide range of climates, and tested how these traits are associated with origin climate. Fifteen genotypes were grown in a greenhouse common garden and harvested to measure growth and drought tolerance traits. Growth traits included absolute and relative growth rate (RGR) and its biomass allocation components. We also considered leaf osmotic potential at full turgor (πo), which is the main determinant of wilting point (i.e., turgor loss point).
Results/Conclusions
Across the 15 Arabidopsis ecotypes, RGR was higher for ecotypes native to colder temperatures, yet RGR and absolute growth were independent of the aridity of the native climate. Leaf density was greater in ecotypes native to warmer climates. The leaf mass per area was higher, and the πo was more negative in ecotypes native to more arid climates. Growth and drought tolerance traits were independent of one another across the genotypes, indicating a lack of a trade-off between growth and drought tolerance across genotypes of a given species, and the potential for traits to adapt independently to various climate stresses, which would contribute to the occupation of a very large climate range in this species. These results emphasize the importance of considering trade-offs and trends at multiple scales, and especially across genotypes of a single species.