Chemical Composition, Physiological and Morphological Variations in Subg. Populations in Response to Different Salinity Levels

This study evaluated the salinity tolerance of five populations of subg. ( and ). The aims of the study were to assess essential oil components, as well as growth and physiological parameters of two species in response to salt stress. Four different levels of salinity (0, 60, 90, and 120 mM NaCl) were applied. The effects of various concentrations of NaCl on essential oil content, composition, growth, water relation, proline, lipid peroxidation (MDA), hydrogen peroxide content, and antioxidant enzyme activity, as well as Na and K contents in leaves and the roots were evaluated. The results revealed that root dry weight loss was higher than that of shoots, indicating root vulnerability due to direct exposure to the salt stress. The lowest and highest oil content was obtained in PATKH (0.6%) at 60 mM and PABAD (0.6%) in 90 mM to 2.16% in PABSM population under 120 mM NaCl. Based on GC-MS analysis, 1,8-cineol (11.64 to 22.02%), camphor (2.67 to 27.14%), bornyl acetate (2.12 to 11.07%), borneol (2.38 to 24.37%), β-caryophyllene (3.24 to 7.58%), α-humulene (2.97 to 7.92%), and δ-3-carene (5.31 to 26.65%) were the most abundant compounds. Based on the principal component analysis (PCA), the most salinity-tolerant populations belonged to species. These populations are characterized by high root stress tolerance index (STI), root elements, and relative water content (RWC) with elevated levels of salinity stress. Finally, the findings might be useful in unraveling the salinity tolerance mechanisms for integrating stress tolerance with medicinal qualities in future studies.