Phosphorus absorption by mycorrhizal extraradical hyphae accelerates plant growth and active ingredient production in Polygonum cuspidatum

Abstract

Arbuscular mycorrhizal (AM) fungi have demonstrated the capacity to increase active ingredient concentrations in industrial plants such as Polygonum cuspidatum, whereas it is still uncertain whether this effect is mediated by AM-facilitated nutritional absorption like phosphorus (P). In this study, a microsystem was utilized to deliver extra P to the hyphal chamber, thereby examining the impacts of hyphal P absorption on plant growth, P acquisition, phosphatase concentration, bioactive compound concentrations, and the expression of resveratrol-related genes in P. cuspidatum. The supplementation of P led to significant increases in Funneliformis mosseae colonization rates in roots and hyphal lengths in soil. AM inoculation significantly improved plant height (34.3–84.7%) and root biomass (10.9–27.8%), particularly when P was supplied to the hyphal chamber. Compared with the uninoculated treatment, AM inoculation also distinctly elevated leaf and root P levels by 110.9–252.2% and 33.0–179.5%, respectively, aligning with an increase in soil acid, neutral, and alkaline phosphatase concentrations. Roots served as the primary site for resveratrol biosynthesis. Inoculation with F. mosseae increased bioactive compound concentrations in both leaves and roots to varying degrees, with the observed increase being greater when hyphae could pass through a 37 μm mesh (permitting hyphal access) into the P-supplemented hyphal chamber, as opposed to a 0.45 μm mesh (restricting hyphal access). Supplying extra P to the hyphal chamber further amplified the promoting effect on root aloe-emodin (23.1%), chrysophanol (28.5%), physcion (14.8%), polydatin (14.7%), and resveratrol (14.4%) concentrations, as well as on leaf chrysophanol (138.0%), physcion (224.5%), and polydatin (113.7%) in AM plants, accompanied by the up-regulated expression of PcCHS1, PcCHS2, PcCRS1, and PcRS genes. In summary, mycorrhizal extraradical hyphal nutrient absorption, especially P, has emerged as a critical mechanism in modulating both plant growth and bioactive compound production in P. cuspidatum.

Graphical Abstract