Ethylene and Abscisic Acid Have Contrasting Regulation During Salt Stress-Induced Inhibition of Seed Germination in Peanut

Plant hormones are chemical messengers that regulate plant development from seed to seed and their adaptation to environmental stress. Salt stress limits food production by inhibiting seed germination and impeding seedling emergence. The Arachis hypogaea L. is an economically important legume crop; however, peanut seed germination and seedling development are affected by soil salinity. The aim of this study was to investigate the significance of ethylene and abscisic acid synthesis in mitigating salt stress during seed germination and the post-germination growth phase in the peanut. Ethylene synthesis in peanut seeds of the cultivar ‘IAPAR25’ was progressively inhibited with increasing NaCl concentration in the germination medium without significant changes in abscisic acid biosynthesis. In contrast, the exposure of seeds of the cultivar ‘Tatu-53’ to NaCl solutions at concentrations of 100, 150, and 200 mM resulted in a significant increase in abscisic acid concentration, but ethylene synthesis by these peanut seeds was not affected by saline conditions. In addition, ‘IAPAR 25’ seeds incubated in increasing concentrations of NaCl exhibited relatively higher germination in comparison with ‘Tatu-53’ seeds. The peanut cultivar ‘IAPAR 25’ was more tolerant to salt stress than the cultivar ‘Tatu-53’, showing little reduction in total dry weight production and a high plant salinity tolerance index. Therefore, different capacities to produce ethylene and abscisic acid by peanut seeds of the cultivars ‘IAPAR25’ and ‘Tatu-53’ explain the differences in salinity tolerance between cultivars.