Investigating the role of tryptophan pretreatment in the acclimation of maize (Zea mays L.) plants to salt stress at physiological and biochemical levels

The aim of this study was to determine the effects of Trp (0.1 mM) seed priming of two maize (Zea mays L.) cultivars (ꞌDKC6590ꞌ and ꞌDKC6724ꞌ) grown under salt stress (0, 25, 50, 100, and 150 mM NaCl). Results showed that NaCl and Trp decreased radicle, root and leaf lengths as well as root and leaf fresh and dry weights of maize (Zea mays L.) plants. RWC and water loss were reduced by salt stress, while Trp did not have any significant effect on RWC and water loss. Osmotic potential (Ѱs) was decreased by salt stress but increased by Trp. Salt stress induced an increase in Na+ content, but decreased K+ content and K+/Na+. In contrast, Trp treatment decreased Na+ content, but increased K+ and K+/Na+. Electrolyte leakage was increased by NaCl but was decreased by Trp application. NaCl decreased Fv/Fm at moderate salt stress levels and increased Fv/Fm at high salt levels, but Trp application decreased Fv/Fm compared to control plants. Chlorophyll a, chlorophyll b, total chlorophyll and total carotenoid contents increased under NaCl conditions, while Trp application had no effect on these parameters. NaCl and Trp treatments increased proline content under high salt stress conditions. Mannitol and sucrose contents increased due to salt stress, while Trp application increased mannitol and sucrose contents under high level salt conditions. Overall, salt stress had negative effects on all parameters and revealed that maize 'DKC6590' variety was more tolerant to salt stress compared to 'DKC6724'. However, Trp application could improve the growth and development of maize plants.