Hydrogen-rich water prepared by ammonia borane can enhance rapeseed (Brassica napus L.) seedlings tolerance against salinity, drought or cadmium

Hydrogen agriculture is recently recognized as an emerging and promising approach for low-carbon society. Since shorter retention time for hydrogen gas (H₂) in conventional electrolytically produced hydrogen-rich water (HRW) limits its application, seeking a more suitable method to produce and maintain H₂ level in HRW for longer time remain a challenge for scientific community. To solve above problems, we compared and concluded that the H₂ in HRW prepared by ammonia borane (NH₃·BH₃) could meet above requirement. The biological effects of HRW prepared by NH₃·BH₃ were further evaluated in seedlings of rapeseed, the most important crop for producing vegetable oil worldwide. Under our experimental conditions, 2 mg/L NH₃·BH₃-prepared HRW could confer 3-day-old hydroponic seedlings tolerance against 150 mM sodium chloride (NaCl), 20% polyethylene glycol (PEG; w/v), or 100 μM CdCl₂ stress, and intensify endogenous nitric oxide (NO) accumulation under above stresses. The alleviation of seedlings growth stunt was confirmed by reducing cell death and reestablishing redox homeostasis. Reconstructing ion homeostasis, increasing proline content, and reducing Cd accumulation were accordingly observed. Above responses were sensitive to the removal of endogenous NO with its scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-1-oxyl-3-oxide (cPTIO; 100 μM), reflecting the requirement of NO functioning in the regulation of plant physiology achieved by NH₃·BH₃-prepared HRW. The application of 1 mM tungstate, an inhibitor of nitrate reductase (NR; an important NO synthetic enzyme), showed the similar blocking responses in the phenotype, suggesting that NR might be the major source of NO involved in above H₂ actions. Together, these results revealed that HRW prepared by NH₃·BH₃ could enhance rapeseed seedlings tolerance against abiotic stress, thus opening a new window for the application of H₂ in agricultural production.