Mechanism of Bacillus pumilus cooperating with silicon to restore carbon metabolism of Glycyrrhiza uralensis Fisch. seedlings exposed to drought stress

Glycyrrhiza uralensis Fisch, widely used in traditional medicine, tobacco flavoring, and food sweetening, faces growth challenges due to drought stress in arid regions. Plant growth-promoting bacteria (PGPB) and silicon (Si) have emerged as effective solutions to mitigate drought effects by enhancing photosynthesis and balanced carbon metabolism, promoting plant growth. This study investigates the impact of Bacillus pumilus (G5), Si, and G5+Si on the carbon metabolism of G. uralensis seedlings under drought stress. Drought stress was induced by maintaining soil moisture at 35 similar to 45 % saturation, and seedlings were treated with G5 (10(8) CFU mL(-1)), Si (2 mM), and both (D+G5, D+Si, D+G5+Si). Results showed that both G5 and Si treatments enhanced carbon metabolism, with the combined G5+Si treatment showing a synergistic effect. Specifically, G5+Si increased chlorophyll levels, boosting photosynthesis and promoting soluble sugar accumulation. This treatment also maintained carbohydrate balance by modulating starch and sucrose metabolism and improved energy conversion by activating glycolysis (EMP) and the pentose phosphate pathway (PPP). Additionally, G5+Si stimulated energy generation by accelerating the tricarboxylic acid (TCA) cycle, enhancing plant growth, and increasing biomass. These findings highlight the synergistic role of G5 and Si in enhancing the drought resilience of G. uralensis seedlings, offering promising strategies for sustainable agriculture and improved crop resilience to climate change.