Salicylic Acid-Regulated Antioxidant Mechanisms and Gene Expression Enhance Rosemary Performance under Saline Conditions

Abstract

Salinity stress as a major agricultural limiting factor may influence the chemical composition and bioactivity of Rosmarinus officinallis L. essential oils and leaf extracts. The application of salicylic acid (SA) hormone may alleviate salinity stress by modifying the chemical composition, gene expression and bioactivity of plant secondary metabolites. In this study, SA was applied to enhance salinity tolerance in R. officinallis. R. officinallis plants were subjected to saline water every 2 days (640, 2,000, and 4,000 ppm NaCl) and 4 biweekly sprays of SA at 0, 100, 200, and 300 ppm for 8 weeks. Simulated salinity reduced all vegetative growth parameters such as plant height, plant branches and fresh and dry weights. However, SA treatments significantly enhanced these plant growth and morphological traits under salinity stress. Salinity affected specific major essential oils components causing reductions in α-pinene, β-pinene, and cineole along with sharp increases in linalool, camphor, borneol, and verbenone. SA applications at 100–300 ppm largely reversed the effects of salinity. Interestingly, SA treatments mitigated salinity stress effects by increasing the total phenolic, chlorophyll, carbohydrates, and proline contents of leaves along with decline in sodium and chloride. Importantly, this study also proved that SA may stimulate the antioxidant enzymatic mechanism pathway including catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) as well as increasing the non-enzymatic antioxidants such as free and total ascorbate in plants subjected to salinity. Quantitative real-time PCR analysis revealed that APX and 3 SOD genes showed higher levels in SA-treated rosemary under salinity stress, when compared to non-sprayed plants. Moreover, the expression level of selected genes conferring tolerance to salinity (bZIP62, DREB2, ERF3, and OLPb) were enhanced in SA-treated rosemary under salt stress, indicating that SA treatment resulted in the modulation of such genes expression which in turn enhanced rosemary tolerance to salinity stress.

Application of seaweed organic components increases tolerance to Fe deficiency in tomato plants

“…However, application of SA, GA and FU x1/10 significantly increased the CAT activity in roots compared to Fe deficient control. Similar results were reported in salt stressed rosemary plants where the application of SA (100-300 mg/L) increased CAT activity [50]. The CAT enzyme catalyze the decomposition of hydrogen peroxide (H 2 O 2 ) into oxygen and water [30].…”

“…Several studies reported positive effects on plant biomass under abiotic stress conditions after the application of SA, GA, SoA, MA, and LA, although none with respect to nutrient imbalance. Related to this, SA application at different concentrations, 0.5 mM (69 mg/L) in seeds of wheat [49], 100-300 mg/L sprayed in rosemary leaves [50] or 0.7-1.4 mM (96-193 mg/L) sprayed in sunflower [51] with high salinity showed a significant increase in FW. Applications in the nutrient solution of 1-2 mM (170-240 mg/L) GA in soybean under low temperatures [22] or applications of 0.75-1 mM (127-255 mg /L) GA in rice under salinity [20] increased the relative growth rate compared to the control.…”

New Tricks for Old Guys: Recent Developments in the Chemistry, Biochemistry, Applications and Exploitation of Selected Species from the Lamiaceae Family

“…Several approaches had been adopted to control salinity adverse effects on plants and one of the more interesting is the use of salicylic acid. The effects of the use of salicylic acid on R. officinalis were studied by Elansary and collaborators . Salinity stress caused the reductions in α ‐pinene, β ‐pinene, and cineole along with increases in linalool, camphor, borneol and verbenone.…”

“…The effects of the use of salicylic acid on R. officinalis were studied by Elansary and collaborators. [174] Salinity stress caused the reductions in α-pinene, β-pinene, and cineole along with increases in linalool, camphor, borneol and verbenone. However, salicylic acid applications at 100-300 ppm largely reversed such effects of salinity.…”

Echophysiological aspects of Ocimum basilicum under saline stress and salicylic acid

“…It also influences fruit productivity, gas exchange, water composition and resistance development to plant diseases. However, the salicylic acid effect will depend on genetic and environmental factors, as well as the application method and dosage (El-Esawi et al, 2017).…”