Effects of ectomycorrhizal fungi (Suillus variegatus) on the growth, hydraulic function, and non-structural carbohydrates of Pinus tabulaeformis under drought stress

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>A better understanding of non-structural carbohydrate (NSC) dynamics in trees under drought stress is critical to elucidate the mechanisms underlying forest decline and tree mortality from extended periods of drought. This study aimed to assess the contribution of ectomycorrhizal (ECM) fungus (<jats:italic>Suillus variegatus</jats:italic>) to hydraulic function and NSC in roots, stems, and leaves of<jats:italic>Pinus tabulaeformis</jats:italic>subjected to different water deficit intensity. We performed a continuous controlled drought pot experiment from July 10 to September 10, 2019 using<jats:italic>P. tabulaeformis</jats:italic>seedlings under 80, 40, and 20% of the field moisture capacity that represented the absence of non-drought, moderate drought, and severe drought stress, respectively.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Results indicated that<jats:italic>S. variegatus</jats:italic>decreased the mortality rate and increased height, root biomass, and leaf biomass of<jats:italic>P. tabulaeformis</jats:italic>seedlings under moderate and severe drought stress. Meanwhile, the photosynthetic rates, stomatal conductance, and transpiration rates of<jats:italic>P. tabulaeformis</jats:italic>were significantly increased after<jats:italic>S. variegatus</jats:italic>inoculation. Moreover, the inoculation of<jats:italic>S. variegatus</jats:italic>also significantly increased the NSC concentrations of all seedling tissues, enhanced the soluble sugars content, and increased the ratios of soluble sugars to starch on all tissues under severe drought. Overall, the inoculation of<jats:italic>S. variegatus</jats:italic>has great potential for improving the hydraulic function, increasing the NSC storage, and improving the growth of<jats:italic>P. tabulaeformis</jats:italic>under severe drought.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Therefore, the<jats:italic>S. variegatus</jats:italic>can be used as a potential application strain for ecological restoration on arid regions of the Loess Plateau, especially in the<jats:italic>P. tabulaeformis</jats:italic>woodlands.</jats:p></jats:sec>