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

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).

Plants were grown under two potassium regimes (K⁺ control C, 3 mM) and (K⁺ deficient KD, 20 µM) in the absence or the presence of 200 µM NaHS (H₂S donor).

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.

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.