**5. Conclusions**

Priming with 0.5 mM of GABA could be an effective technique to alleviate salinity and osmotic stresses and OS+S causing inhibition of rice seed vigor. Under the stress conditions, GABA induced a balance in Na+/K<sup>+</sup> accumulation and transport from the root to the leaf which could be attributed to the osmotic adjustment through the mobilization of organic osmolytes such as proline, sugars, and starch during seed germination. The fluorescence staining revealed that H2O2 formation was increased under the stress condition and decreased by the GABA priming treatment. These findings indicated that GABA could also act as a signal molecule under salinity, osmotic stress and their combination by increasing antioxidant enzymes, phenolic metabolism-related enzymes and detoxification-related enzyme activities and their transcript levels. The significantly improved starch and sugar contents and *CIPK* gene expression in rice seedlings by GABA treatment under the stress conditions may be the main mechanism of rice tolerance to salinity, osmotic stress and their combination. The present study elucidated the possible cross talk between the salinity and osmotic stresses when the plant are exposed to both at the same time, and thus to develop transgenic crops with enhanced tolerance to field conditions, further studies need to expand their area to include stress combinations. Current findings provide new evidence for better understanding of GABA-regulated osmotic and salinity combined stress tolerance during seed germination and development. The results showed that the different abiotic stresses induced changes in cell cycle progression resulting in inhibition in rice root cell development. Priming with 0.5 mM GABA has the potential to improve cell ultra-morphology under the stress condition.
