Seed-bulb quality determines yield and quality in Longya Lily: A biochemical and metabolic study

• Seed-bulb weight positively correlates with LBP yield/quality in Longya Lily. • Heavier seed-bulbs have more water-soluble proteins, key starch enzymes, and auxins. • Lighter seed-bulbs accumulate more bioactive secondary metabolites. In this study, Longya Lily ( Lilium brownii var. viridulum Baker) seed-bulbs were graded into three grades based on individual weight. Chemical composition, metabolic enzyme activity, phytohormone levels, and metabolomic profiles were systematically analyzed, and the yield and quality of the resulting Longya Lily bulb products (LBPs) were evaluated. Results showed that LBPs derived from first grade seed-bulbs had significantly greater individual weight (average 400 g), water-soluble protein content (80 mg/g), and total amino acid content (1901 μg/g) compared to those from third grade seed-bulbs (224 g, 65 mg/g, and 1053 μg/g, respectively). Biochemical analyses revealed that first grade seed-bulbs contained significantly higher levels of water-soluble proteins, auxins, salicylic acid, and key starch-sucrose metabolic enzymes (e.g., starch phosphorylase and soluble starch synthase). They also exhibited more active primary metabolism, characterized by higher levels of amino acids, nucleosides, and lipids. In contrast, third grade seed-bulbs displayed elevated levels of jasmonates, abscisic acid, and secondary metabolites (including terpenoids, flavonoids, and alkaloids), along with increased lipid peroxidation. These findings demonstrate that seed-bulb weight governs productivity through differential metabolic allocation: heavier seed-bulbs prioritize growth-related primary metabolism, whereas lighter seed-bulbs activate defense-oriented secondary metabolism. This study provides a theoretical basis for establishing objective seed-bulb quality grading standards.