Objectives Green, sustainable, and high economic return are the primary requirement for ecological remediation of mining areas. We examined the effects of different methods for applying dark septate endophytes (DSE) strains on growth, nutrition quality and photosynthetic efficiency of Morus alba L., to provide an efficient biological remediation method.

Methods The study was carried out in the reclaimed area of Morus alba L. in Halagou coal mine in Shenmu City, Shaanxi Province. DSE extracellular metabolites were applied in three methods, including: leaf spreading (L), watering root (R), and leaf spreading + watering root (LR), and clear water was used as control. The growth, photosynthetic indexes, and the nutrients and nutrition quality indexes of Morus alba L. were determined. The ecological effects of Morus alba L. reclaimed area under different treatments were evaluated by principal component analysis, and the optimal application method of DSE extracellular metabolites was explored.

Results Application of DSE promoted the growth and nutrient absorption, and significantly increased the plant height, ground diameter, leaf N, P and K contents of Morus alba L. compared with the control, LR treatment significantly increased leaf transpiration rate and net photosynthetic rate of Morus alba L. by 329.4% and 207.1%, respectively, enhanced soluble sugar content of Morus alba L. by 19.8%; L and R treatment significantly increased the cellulose and protein contents of Morus alba L. According to the principal component analysis, LR treatment had the highest comprehensive score, while the control treatment had the lowest comprehensive score.

Conclusions DSE extracellular metabolites application method of leaf spreading combined with watering root shows the most satisfactory effect on promotion of Morus alba L. nutrient uptake and photothynthetic efficiency, which is conducive to promote the growth and nutrition quality, and the bioremediation effect of Morus alba L. as well.