Effects of Foliar Potassium Fertilizer on Photosynthetic Capacity and Expression of Potassium and Sugar Transporters in Peach (Prunus persica)

Potassium (K+) is a vital macronutrient for plant growth and stress resilience, with KT/HAK/KUP transporters playing a central role in its homeostasis. Although these transporters are known to influence photosynthesis, the molecular mechanisms by which fertilization promotes assimilate accumulation in peach crops remain poorly understood. In this study, 17 PpHAK genes were identified based on the peach genome and classified into four distinct clades through phylogenetic analysis, a classification further supported by conserved gene structures and motifs. Interspecific collinearity analysis revealed that transporters are highly conserved among Rosaceae species. Physiological measurements demonstrated that foliar application significantly enhanced photosynthetic capacity, as evidenced by a 33% increase in net photosynthetic rate (Pn) and improved photoelectron yield (Y(II)). At the same time, the transcript levels of the transporters PpHAK1, PpHAK5, and PpHAK9 were significantly upregulated, as confirmed by quantitative real-time RT-PCR (qRT-PCR) analysis. Furthermore, the expression of genes involved in sugar metabolism and transport, particularly PpPLT5-1, was significantly induced. Collectively, these results indicate that foliar K+ application enhances photosynthesis and promotes assimilate accumulation by modulating the expression of both K+ and sugar transporters. These findings offer a theoretical basis for optimizing nutrient management to improve fruit quality in stone fruit production.