Aims An ectomycorrhizal fungus (ECMF) may enhance plant drought resistance. However, there is limited information regarding the effects of ECMFs on drought resistance in Pinus massoniana Lamb., a native species representing an afforestation pioneer tree in subtropical regions of China. Methods In this study, a pot experiment was conducted to determine the effects of ECMF Suillus luteus inoculation on the root morphology and endogenous hormones of P. massoniana, including roots, leaves, and stems, under various water treatment conditions. Four water levels (regular, light, moderate, and severe drought) and three inoculations (inoculated Suillus luteus, numbered S12 and S13, and non-ECMF-inoculated) were compared using a factorial design. Results Under drought stress, P. massoniana seedlings inoculated with S12 and S13 had significantly increased root morphology development (p < 0.05). Light drought positively influenced root development, resulting in a more than twofold increase in root length and root surface area compared to non-inoculated seedlings. Concentrations of gibberellic acid (GA), zeatin riboside (ZR), and indole-3-acetic acid (IAA) in roots, stems, and leaves of inoculated S12 and S13 plants were elevated, whereas abscisic acid (ABA) concentrations were significantly lower, compared to non-inoculated seedlings. The ABA concentrations in the roots of S12 and S13 inoculated seedlings under light drought stress were 1.5 times lower than those in non-inoculated controls. Moreover, root development was positively correlated with plant total GA, IAA, and ZR but negatively correlated with ABA. ConclusionsS. luteus can promote the root growth and development of P. massoniana seedlings, notably by regulating the balance in the concentration of endogenous hormones, thus improving the drought resistance of P. massoniana seedlings.

Ectomycorrhizal fungi can absorb heavy metals and allow host plants to develop resistance to heavy metal stress, but their heavy metal tolerance is not fully understood. In this study, the ability of Suillus bovinus (Sb) and Suillus placidus (Sp) to tolerate cadmium (Cd) was evaluated. Sb and Sp were treated with different Cd concentrations (0 (control), 0.2, 0.4 and 0.8 mg/L) under pure culture conditions, and the biomass, osmotic adjustment substance contents (soluble sugar and soluble protein), antioxidant enzyme activities (superoxide dismutase (SOD) and catalase (CAT)), pH and conductivity were examined. Sb biomass, soluble protein content and SOD activity first increased (0.2 mg/L and 0.4 mg/L Cd) and then decreased (0.8 mg/L Cd). Sp showed a similar change rule but a smaller range. Cd treatment increased the CAT activity of Sb and Sp but significantly reduced soluble sugars in Sb mycelium, whereas 0.2 mg/L Cd significantly increased soluble sugars in Sp mycelium. The pH and conductivity in the medium of Sb treated with different Cd concentrations showed more significant changes than those of Sp. The pH of Sp at 0 mg/L Cd and conductivity at 0.8 mg/L Cd were significantly lower than those of Sb. Correlation analysis suggested that Cd affected Sb more than Sp. In general, Cd treatment had less effect on the indexes of Sp, and Sp tolerated Cd better than Sb.