| چکیده انگلیسی مقاله |
Background and objectives: Creeping savory is a medicinal and perennial plant that grows in the north and northwest of Iran. The essential oil of this plant has antibiotic properties and is used in herbal medicines, food preparation, and health products. Salinity stress has adverse effects on photosynthetic processes and plant growth and yield. Salicylic acid protects plants against stress by regulating many physiological and enzymatic processes. So far, not much information has been published about the effect of salicylic acid on the physiological process, morphologically, and yielding traits of creeping savory under salinity stress conditions.
Methodology:
This factorial experiment was implemented in the greenhouse of the Kermanshah Agricultural and Natural Resources Research Center based on a Completely Randomized Design including four levels of salinity (0-50-100-150 mM) and two levels of salicylic acid (0 and 2 mM). Chlorophyll fluorescence (Fv/Fm) was measured with a Hansatech, UK Pocket PEA device. The chlorophyll index (SPAD) was measured with a SPAD-502Plus device, Minolta, Japan. Leaf proline content and soluble protein were measured based on Bradford method using a Bio Tek PowerWave XS2 Microplatereader, USA. Various morphological and yield traits such as plant height, leaf area (by a Light Box device, ADC, UK), leaf fresh weight, root fresh weight, and shoot fresh weight (g) were measured. Leaf dry weight, root dry weight, and shoot dry weight were weighed after drying the samples at 75°C for 48 hours. Relative water content (RWC) was calculated. Leaf electrical conductivity (µS/cm) was measured with an EC COND 3110, WTW (Germany). Analysis of variance and comparison of means (Dunkan test) were performed using IBM SPSS Statistics (Ver. 26).
Results: The highest plant height (92.7 cm), leaf area (0.8 cm2), shoot fresh weight (26.9 g), and shoot dry weight (9.15 g) were obtained at 0 mM NaCl + 2 mM SA. The highest leaf fresh weight (13.5 mg), leaf dry weight (2.5 mg), quantum yield of photosystem II (0.80), and photosynthetic index (37.0) were observed at 50 mM NaCl + 2 mM SA. The highest root fresh weight (27.3 grams), root dry weight (4.3 grams), and the highest relative water content (91.7 percent) were obtained at 0 mM NaCl. The highest proline (12.7 μg/g) was observed at 150 mM NaCl and the highest soluble protein (1.1 mg/g) was observed at 100 mM NaCl + 2 mM SA. The use of 2 mM salicylic acid, under salinity stress conditions, increased plant height (16.4%), leaf area (18.6%), leaf fresh weight (17.3%), shoot fresh weight (35.4%), shoot dry weight (35.8%), relative water content (8.4%) and soluble protein by 41.4%, but decreased proline content (41.4%) and electrical conductivity (49.4%). Applying 2 mM salicylic acid has a significant effect on root fresh weight, maximum quantum yield of photosystem II and chlorophyll index in mild salinity conditions. Also, SA increased leaf dry weight in mild salt stress but decreased it in severe salinity conditions.
Conclusion: This research showed that applying salicylic acid under salinity stress causes changes in some morphophysiological, photosynthetic, and biochemical characteristics of creeping savory. Increasing the salinity levels decreased some photosynthetic, physiological, vegetative, and yield traits, but the content of some osmotic regulators, such as proline and protein, was increased. The application of 2 mM salicylic acid improved some of the adverse effects of salinity in creeping savory at different salinity levels, enhancing growth and yield traits in the salicylic acid-treated plants. Applying two mM salicylic acid increases the tolerance of creeping savory against salinity stress by increasing the osmotic protectants and inducing the activity of antioxidant systems. Based on the research results, growing this plant in soils with a salinity of more than 100 mM is not recommended. Also, in the case of planting creeping savory in saline soils (less than 100 mM), to increase plant growth and farmers' income, it is recommended to apply two mM salicylic acid as a foliar spray. |