Nitric oxide improves the germination of wheat seeds exposed to salinity via modulating sugar and proline metabolism

Abstract

There is a large body of evidence showing the positive effect of nitric oxide (NO) on the growth of plants subjected to abiotic stress but less is known regarding the physiological responses of NO-treated seeds to harsh environmental conditions. Therefore, the aim of this study was to determine NO-mediated physiological alterations in germinating bread wheat seeds under salinity. In this regard, NaCl-exposed wheat seeds were germinated in petri plates containing various concentrations of sodium nitroprusside dehydrate (SNP, 25 to 500 µM) for 7 days. Different chemicals, such as potassium ferrocyanide, potassium cyanide, and carboxy-PTIO potassium salt were also used to confirm NO action on germination. Finally, physiological parameters associated with reserve mobilization, oxidative and antioxidative status, and osmoregulation were assayed in wheat seeds treated with NaCl and/or SNP for 2 days. The results showed that 250 µM SNP supplementation significantly improved the germination of wheat seeds exposed to 405 mM NaCl. It was verified that the stimulating effect of SNP on seed germination was not related to molecules (e.g., cyanide and iron) other than NO. In addition, SNP treatment markedly enhanced the activity of alpha-amylase, resulting in an increment in the reducing sugar content of wheat seeds subjected to salt stress. Moreover, 250 µM SNP led to a considerable increase in the proline accumulation in seeds under both control and excess salt conditions (p < 0.05). In conclusion, the current work provides evidence that NO can improve salinity-induced germination inhibition in wheat seeds by regulating sugar and proline metabolism.