Glutathione‐induced hydrogen sulfide enhances drought tolerance in sweet pepper (Capsicum annuum L.)

Abstract Glutathione (GSH) has been studied for its potential to enhance stress tolerance in plant systems, but the role of hydrogen sulfide (H 2 S) in GSH‐induced water stress tolerance in sweet pepper ( Capsicum annuum L.) is still under investigation. This study explores how H 2 S and GSH modulate water stress tolerance in pepper plants, addressing a research gap. The joint effect of sodium hydrosulfide (NaHS), a donor of H 2 S, and GSH on water stress tolerance was determined through pre‐treatment with the H 2 S scavenger 0.1 mM hypotaurine (HT). Pepper seedlings were sprayed with 1.0 mM GSH or GSH + 0.2 mM NaHS once a week, with soil moisture content set at 80% and 40% for full irrigation and water stress conditions for a duration of 2 weeks. The results showed that water stress significantly reduced total plant dry weight, chlorophyll a and b content, Fv/Fm , leaf water potential, and relative water content by 50%, 56%, 33%, 27%, 52%, and 34%, while increasing hydrogen peroxide (H 2 O 2 ), proline, and H 2 S levels by 152%, 134%, and77%, respectively. Treatment with GSH and NaHS reduced water stress‐induced H 2 O 2 production and improved plant growth, photosynthetic traits, proline, and the activity of L‐cysteine desulfhydrase (L‐DES), leading to the generation of H 2 S content. GSH reduced NADPH oxidase (NOX), superoxide dismutase (SOD), and H 2 O 2 but increased glutathione peroxidase (GPX) activities. The interaction of NaHS and GSH led to further reductions in NOX, SOD, and H 2 O 2 values but increased GPX activity. The combined GSH and NaHS treatment increased nitric oxide (NO) production but decreased the activity of S ‐nitrosoglutathione reductase (GSNOR), potentially accelerating S ‐nitrosylation. Hypotaurine negated the positive impacts of GSH on water stress tolerance by reducing H 2 S concentration in pepper plants, but this was corrected by the concurrent application of NaHS and GSH + HT. Therefore, water stress tolerance requires H 2 S.