Foliar medium-modulus liquid potassium silicate enhances tobacco yield and chemical coordination through elemental homeostasis and energy-driven metabolic reprogramming

Abstract

Insufficient K content and uncoordinated chemical compositions represent critical bottlenecks limiting the industrial value of flue-cured tobacco. This study investigated the effects of foliar-applied liquid potassium silicate (SikL) on the yield and quality of Nicotiana tabacum cv. Yunyan 87 and its metabolic mechanisms. Field experiments revealed 1500 mg/L as the optimal concentration, significantly increasing yield and output value by 16.53% and 27.79%, respectively, relative to the control, outperforming traditional KH₂PO₄. Physiologically, SikL significantly increased the K and Si content in the leaves and led to a non-significant downward trend in Na accumulation, thereby optimizing ionic homeostasis. Regarding quality, SikL effectively improved the carbon-nitrogen (C/N) balance, refining the reducing sugar/nicotine ratio from an uncoordinated 13.58 to an ideal range (8.79–9.58) and significantly increasing the chemical composition coordination score (P).Metabolomic analysis confirmed that SikL induced systemic metabolic reprogramming: it strengthened the energy metabolism infrastructure by up-regulating energy cofactors ( FAD and pantothenate); redirected metabolic flux toward nitrogen pathways (e.g., arginine and glutamate) to provide precursors for nicotine synthesis, thus optimizing the C/N ratio; and activated phenylpropanoid and flavonoid pathways to promote the accumulation of lignin monomers and antioxidants. These changes synergistically enhanced tobacco yield, chemical coordination, and physiological defense. Furthermore, a decline in performance at 2000 mg/L confirmed a concentration threshold effect. In conclusion, foliar application of 1000–1500 mg/L SikL is an efficient strategy for enhancing tobacco yield and quality through energy-driven metabolic reorganization centered on C/N balance.