Application of growth promoting hormones alters the composition and antioxidant potential of dill essential oil under salt stress.

The performance of dill plant may be affected by adverse environments such as salinity. Thus, this research was designed to evaluate changes in chemical composition and antioxidant activity of seed essential oil of dill (Anethum graveolens L.) in response to salinity (0, 5, 10 and 15 dS/m) and 1 mM of each hormonal treatments (gibberellic acid, salicylic acid, and cytokinin). Salicylic acid (SA) reduced Na+ content of roots and leaves by 15.4%, 30.9% and 12.4%, 24.3%, but enhanced K+ content by 29.8%, 51.6% and 76.6%, 73.4% under moderate and severe salinities, respectively. Essential oil yield was enhanced with progressing seed filling, despite decreasing essential oil percentage. Percentage of essential oil was increased under low and moderate salinities. Hormonal treatments, particularly SA enhanced seed mass and essential oil percentage, leading to enhanced essential oil yield. The amounts of most constituents were enhanced under moderate salinity. Foliar spray of SA and CK (cytokinin) increased almost all essential oil components, except dill ether and dill apiole, while the GA3 (gibberellic acid) treatment reduced most of the constituents. The α-fenchol was only induced by salt stress. The ß-pinene, 1-terpineol, cryptone, oxypeucedanin hydrate, α-thujene and P-α-dimethylstyrene were also specifically synthesized in SA treated plants under salinity. The highest TPC (total phenolic content) and antioxidant activity were recorded for essential oil of SA treated plants at mass maturity under moderate salinity. In general, the SA spray was the most effective treatment for improving essential oil quantity and quality of dill plants.

Effect of lignite on alleviation of salt toxicity in soybean (Glycine max L.) plants.

Salt toxicity of agricultural land is a natural phenomenon which is due to agricultural irrigation. This toxicity is harmful to crop productivity via increasing oxidative stress products. In a factorial controlled trial, four levels of lignite-enriched soil (soil lignite content: none, 50, 75 and 100 g kg-1) were exposed to three levels of soil salinity (0, 5 and 10 dS m-1 NaCl). Then reactive oxygen species (ROS) generation (hydrogen peroxide and superoxide radical), lipid peroxidation, antioxidant enzymes activities (peroxidase, catalase and super oxide dismutase), proline, glycine betaine, soluble sugars and soluble protein contents of soybean plants were compared across different lignite concentration and saline toxicity. Under the 5 and 10 dS m-1 NaCl, sodium entry to the leaf and root cells, hydrogen peroxide concentration, superoxide radical generation, lipid peroxidation and osmoprotectants creation increased and consequently plant growth reduced (12-49%). Lignite applications by improving the cation exchange capacity of soil (8-16%), enriched the leaf and root cells with potassium (5-26%), calcium (40-56%), magnesium (30-42%) and inhibited the sodium entry to the cells, and consequently increased potassium/sodium ratio and reduced oxidative stress, antioxidant activities and synthesis of osmoprotectants in soybean leading to increased plant biomass (18-37%). Lignite usage in 75 and 100 g kg-1 soil showed a better effect than 50 g kg-1 soil on reducing harmful effects of salt toxicity. Soil enrichment with lignite improves plant tolerance to salt toxicity via decreased oxidative stress.