Effects of Potassium Application on Lilium davidii var. unicolor Growth, Polysaccharide Accumulation, and Metabolism

Abstract

Lilium davidii var. unicolor is an important variety of lily with high economic, ornamental, edible, and medicinal values. Up to now, the research on polysaccharide as the main active substance is not vast, especially the effect of potassium on lily polysaccharide. Here, we investigated the effects of potassium fertilizer application on the growth and development, polysaccharide accumulation in the bulb, and differential metabolites in L. davidii var. unicolor. It was treated with fixed amounts of nitrogen (N) and phosphorus (P), and four K concentrations comprising K0 (0 mg·L−1), K1 (447.6 mg·L−1), K2 (671.4 mg·L−1), or K3 (895.2 mg·L−1). The growth indexes were determined for L. davidii var. unicolor under different K concentrations in different growth stages. The polysaccharide contents of the bulbs were determined using the sulfuric acid−phenol method. An analysis of the differential polysaccharide metabolites was also conducted. The application of potassium promoted the growth and increased the bulb polysaccharide content of L. davidii var. unicolor, and the most suitable K concentration of 671.4 mg·L−1 had the most significant effects. Non-targeted metabolomics analysis screened 37 differential polysaccharide metabolites under K0 and K2, where 25 were significantly upregulated and 12 were significantly downregulated. Three metabolic pathways were enriched in polysaccharide-related differential metabolites, i.e., the galactose metabolism, amino sugar and nucleotide sugar metabolism, and starch and sucrose metabolism. The results could provide a theoretical basis for an improved fertilization management and the high-quality cultivation of L. davidii var. unicolor.