Effect of <em>Zataria multiflora</em> Boiss. Extract and Nano-Extract on Inducing Salt Stress Tolerance of<em> Ocimum basilicum</em> L.var. Genovese Under Floating Culture

In order to investigate the effect of Zataria multiflora Bioss. extract and nano-extract on morphophysiological, phytochemical indices, yield, and essential oil compositions of basil (Ocimum basilicum L.var. Genovese) under salinity stress (0, 25, 50, and 100 mM NaCl), an experiment was conducted as split-plot design in a basic block with complete randomization with three replications. The results of this study showed that the highest levels of root and shoot fresh weight, total chlorophyll, total phenol, flavonoid, antioxidant activity (DPPH and FRAP), proline, catalase enzyme and phenol alanine ammonia lyase (PAL) enzyme were observed in the Z. multiflora nanoextract treatment. The highest level of potassium was observed in conditions without salinity stress and foliar spraying with Z. multiflora extract. The highest level of O. basilicum L.var. Genovese sodium was observed in the 100 mM salinity treatment and the lowest level was recorded in the nanoextract treatment in conditions without salinity stress. In this study, the results of essential oil analysis indicated the identification of 39 compounds in which linalool, eugenol, carotenoid, methyl chavicol, A-Humulene and menthol were identified as the main compounds. In this study, the effect of nano-extract on the content of essential oil compounds was evident. The results of the study showed that there was a positive correlation between the traits of fresh and dry weight of shoots, fresh and dry weight of roots, total chlorophyll and potassium. While sodium showed a negative correlation with the traits of fresh and dry weight of shoots, fresh and dry weight of roots, total chlorophyll and potassium. Principal component analysis showed that the combination of the first two components accounted for 89.28% of the variations. Among all treatments, Z. multiflora nanoextract, while moderating the effects of stress, showed the highest efficiency in improving the morphophysiological, biochemical traits, and essential oil content and secondary metabolites of O. basilicum L.var. Genoves.