Exogenous hydrogen sulfide mitigates potassium deficiency in Brassica napus plants by modulating growth and photosynthetic activity and regulating hydrogen sulfide and nitric oxide biosynthesis

Background and aims Potassium (K+) deficiency is a major abiotic stress that severely hampers plant growth and development. Hydrogen sulfide (H2S), a signal molecule regulating several critical functions in plants, is involved in plant tolerance to various environmental stresses. However, its involvement in the alleviation of K+ deficiency is not yet elucidated. The objective of the present work was to study the effects of K+ deficiency-H2S interaction on Brassica napus (rapeseed). Methods Plants were grown under two potassium regimes (K+ control C, 3 mM) and (K+ deficient KD, 20 mu M) in the absence or the presence of 200 mu M NaHS (H2S donor). Results Results demonstrated that K+ deficiency reduced plant growth, pigment and soluble sugar concentrations, as well as diminished photosynthetic activity. Notably, photosystem II (PSII) was more affected than photosystem I (PSI), as indicated by modulated chlorophyll measurements. The exogenous application of NaHS significantly alleviated these negative effects induced by K+ deficiency. This amelioration was associated with increased activity of L/D-cysteine desulfhydrase (LCD and DCD) enzymes, which contributed to maintaining adequate endogenous H2S and nitric oxide (NO) concentrations. These balanced levels of H2S and NO improved rapeseed plants' ability to cope with K+ deficiency stress. Conclusion This study suggests a synergistic action of H2S and NO in mitigating K+ deficiency stress by enhancing plant growth, photosynthetic capacity, and energy conversion in both photosystems. This research implies that H2S could serve as a sustainable solution to boost plant growth and productivity, potentially ensuring food security, particularly in underdeveloped economies.