The root characteristics promoted higher water use efficiency and stronger drought tolerance in invasive Compositae plants

Abstract Purpose Root traits affect the response of invasive plants to drought. Understanding the differences in root traits between native and invasive plants could therefore help improve our understanding of invasive plant performance under changing water conditions. Methods Root morphological and physiological traits as well as water use parameters associated with water use efficiency were compared in soil-cultured native and invasive Compositae plants under well-watered and drought stress conditions. Seedlings of five invasive and five genetically-related native species were examined via paired-methods. Results Under drought stress, compared with the native plants, invasive plants had a more positive root and leaf water potential, longer fine root length (diameter ≤ 0.5 mm), larger specific root length and lower water consumption. Especially, invasive plants maintained a higher biomass, higher instantaneous and biomass water use efficiencies than the native plants, although drought inhibited all plants growth and invasive plants had similar root hydraulic conductivity with native plants. Changes in water use efficiency in the invasive plants were mainly regulated by the fine root length (diameter ≤ 1 mm), specific root length, and root water potential; however, in native plants, only the fine root length (diameter ≤ 1 mm) had an effect, regardless of the water conditions. Conclusion Together, a more positive root water potential, and longer and thinner fine roots (diameter ≤ 1 mm) are associated with improvements in water use efficiency and drought tolerance in invasive plants, suggesting that physiological and morphological root characteristics play an important role in the success of plant invasion.