Foliar-applied potassium improved mycorrhizal Goji (Lycium barbarum L.) growth of the potassium free- compartment in a compartmented culture system

Arbuscular mycorrhizal (AM) fungi promote plant mineral nutrient acquisition, and AM fungal hyphae can transport water and nutrients. Potassium has significant effects on plant photosynthesis, stomatal conductance, and other physiological processes. However, it is little known whether foliar-applied potassium in one plant could affect the nearby plant that connected by the AM fungal hyphae network. We analyzed the effects of foliarapplied potassium (2% K2SO4) in the potassium additional compartment (potassium was foliar-sprayed on plant in this compartment) on growth, photosynthesis, chlorophyll fluorescence parameters, potassium content, and the relative expression of potassium channel/transporter genes (LbHAK, LbKAT3, LbAKT2, LbKT1, and LbSKOR) of mycorrhizal Lycium barbarum in the potassium-free compartment (potassium was not foliar-sprayed on plant in this compartment) via AM fungal hyphae network of a three compartments culture system (the system contains three compartments, namely two root compartments on the left and right and a hyphal compartment in the middle). Compared with inoculation of Rhizophagus irregularis, foliar-applied potassium improved growth, photosynthesis, and potassium content of mycorrhizal L. barbarum in the potassium-free compartment, but had no effect on mycorrhizal L. barbarum chlorophyll fluorescence parameters. Additionally, foliar-applied potassium increased the relative expressions of LbHAK, LbKAT3 LbKT1 and LbSKOR in roots of mycorrhizal plants in the potassium-free compartment, while the relative expression of LbAKT2 in shoots of mycorrhizal plant was increased in the potassium-free compartment. This study suggests that AM fungal hyphae network transports potassium to the potassium-free compartment, then potassium regulates the expression of potassium channel/ transporter genes to promote potassium uptake and transport, thus improves photosynthesis, and ultimately, promotes the growth of mycorrhizal L. barbarum in the potassium-free compartment.

Automated summary

This study found that foliar-applied potassium has a promoting effect on the growth, photosynthesis, and potassium content of mycorrhizal plants. It can be transported to the potassium-free compartment through the AM fungal hyphae network, then regulate the expression of potassium channel/transporter genes to improve potassium uptake and transport, thus enhancing photosynthesis and ultimately promoting the growth of mycorrhizal plants.