Impact of Ectomycorrhizal Symbiosis on Root System Architecture and Nutrient Absorption in Chinese Chestnut and Pecan Seedlings

Ectomycorrhizal (ECM) symbiosis can alter root tip structures; but the detailed mechanisms behind these changes and their impact on overall root architecture remain unclear. This study aimed to investigate the effects of ECM inoculation with Cenococcum geophilum (Cg) and Pisolithus orientalis (Po) on root growth, nutrient levels in shoots, and enzyme activities in soil for Chinese chestnut (Castanea mollissima) and pecan (Carya illinoinensis) seedlings. Chestnut and pecan seedlings were inoculated with Cg or Po. The growth parameters, including root and shoot development, were assessed. Nutrient levels of nitrogen, phosphorus, and potassium in the shoots were measured, and soil enzyme activities related to carbon, nitrogen, and phosphorus cycles, such as β-glucosidase, peroxidase, N-acetylglucosaminidase, and acid phosphatase, were quantified. Inoculation with ECM fungi significantly enhanced root growth, especially fine roots, and improved nutrient accumulation in the shoots of both seedlings. Cg and Po inoculation increased nitrogen, phosphorus, and potassium levels in the shoots. Moreover, the soil enzymes involved in the carbon, nitrogen, and phosphorus cycles, such as β-glucosidase, peroxidase, N-acetylglucosaminidase, and acid phosphatase, showed elevated activity levels under ECM inoculation. Notably, Cg inoculation elevated peroxidase activity, which is linked to root development and soil hormone regulation. ECM symbiosis, especially with Cenococcum geophilum, positively influences root structure and nutrient absorption, enhancing seedling growth in chestnut and pecan. These findings highlight the role of ECM fungi in improving plant growth, particularly under conditions of limited colonization.