Does seed priming induce changes in the levels of some endogenous plant hormones in hexaploid wheat plants under salt stress?

In order to assess whether salt tolerance could be improved in spring wheat (Triticum aestivum L.), the present study was performed by soaking the seeds of two cultivars, namely MH-97 (salt sensitive) and Inqlab-91 (salt tolerant), for 12 h in distilled water or 100 mol/m(3) CaCl2, KCl, or NaCl. Primed seeds from each treatment group and non-primed seeds were sown in a field in which NaCl salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCl and NaCl, was found to be effective in alleviating the adverse effects of salt stress on both wheat cultivars in terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance in plants of both cultivars. In MH-97 plants, CaCl2 pretreatment considerably reduced leaf abscisic acid (ABA) concentrations and increased leaf free salicylic acid (SA) concentrations under both saline and non-saline conditions. In contrast, in the Inqlab-91 plant, CaCl2 increased free indoleacetic acid (IAA) and Indolebutyric acid (IBA) content. However, priming of seeds with CaCl2 did not alter free polyamine levels in either cultivar, although spermidine levels were considerably lower in plants raised from seeds treated with CaCl2 for both cultivars under saline conditions. Priming with KCl increased growth in Inqlab-91 plants, but not in MH-97 plants, under saline conditions. The salinity induced reduction in auxins (IAA and IBA) was alleviated by NaCl priming in both cultivars; under saline conditions. However, NaCl increased leaf free ABA content and lowered leaf SA and putrescine levels in lnqlab-91 plants under saline conditions. In conclusion, although all three priming agents (i.e. CaCl2, KCl, and NaCl) were effective in alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different in the two cultivars.