Arbuscular mycorrhizal fungi regulate mineral element distribution in grapevines under pH stress

Grapevine (Vitis vinifera L.) productivity is closely linked to soil stability, and pH is a master variable controlling both plant development and the bioavailability of essential mineral elements (Mg, Ca, Fe, Cu, Zn). This study investigates the growth-promoting effects of arbuscular mycorrhizal fungi (AMF) on grapevines under different soil pH environments. The results indicate that compared to pH 6.5, the relative electrical conductivity (REC) of leaves, root malondialdehyde (MDA), and reactive oxygen species (ROS) increased at pH 5 and pH 8, affecting the absorption and transport of Mg, Ca, Fe, Cu, and Zn, thereby inhibiting the growth and development of grapevines. Inoculation with the AMF Septoglomus viscosum and Glomus chinensis significantly enhanced the activities of superoxide dismutase (SOD) and peroxidase (POD) by activating the root antioxidant system, thereby alleviating the impact of pH stress on grapevine growth and development. Under pH 8 condition, the effects were more pronounced, with G. chinensis significantly increasing plant fresh weight (103.06%), net photosynthetic rate (53.99%), root vitality (108.70%), ferric chelate reductase (FCR) (54.80%), and POD (49.23%), while significantly reducing leaf REC (33.33%) and root MDA content (35.79%). S. viscosum facilitated the root absorption and upward transport of Mg and Ca, significantly promoting the accumulation of Zn and Cu in the roots and inhibiting their transport to the above-ground parts, thereby alleviating heavy metal stress on the leaves. Overall, the addition of AMF significantly improves the distribution of Mg, Ca, Fe, Zn, and Cu within grapevines, enhancing leaf and root functions as well as biomass accumulation under acid-base stress conditions. These findings demonstrate that S. viscosum and G. chinensis differentially promote grapevine performance across pH gradients, offering mechanistic insights into pH-dependent mineral nutrient homeostasis. They provide a theoretical basis for using AMF-based biotechnologies in sustainable viticulture to enhance stress resilience and fruit quality.