The Effect of Biofertilizer and Salicylic Acid on Quantitative and Qualitative Traits of Satureja hortensis L. under Drought Stress Conditions

Introduction  Satureja hortensis L. is an annual herbaceous plant of the mint family that has numerous raised or creeping stems or arched stems with a height of 10 to 30 cm. The height of this plant reaches a maximum of 60 cm. The stems and branches are usually covered with hairs. The leaves are opposite, have short or almost no petioles. The leaves are opposite, the petioles are short or almost without petioles, there are many small spots on the surface of the leaf called the tuber, which contains the essential oil. Knowledge of environmental, plant and agro-factors play an important role in the success of medicinal plants. One of the factors affecting the growth and development and production of active ingredients of medicinal and aromatic plants is water, the lack of which has a greater effect on reducing production than other inputs. Drought stress is an important global constraint on agricultural production and food security. Recently, there has been a growing interest in reducing the use of chemical fertilizers and exploring alternative methods for producing high-quality crops. This is particularly important in arid and semi-arid regions like most parts of Iran, where soil nutrient levels are often low. The use of biofertilizers can help strengthen plants and promote sustainable crop production. The objective of this study was to examine the impact of salicylic acid foliar application, Mycorrhiza-Azotobacter bio-fertilizers, and drought stress on the morphological and physiological characteristics of summer savory, a medicinal plant. Materials and Methods This experiment was conducted to evaluate some traits of summer savory in response to biological fertilizers, salicylic acid and drought stress in Zamanabad village of Rey city (Tehran province) during 2018 and 2017. This experiment was conducted using a randomized complete block design with three replications, as a factorial split plot. The main factor was irrigation, with three levels including soil moisture potential (as a control), potential of -5.5 atmospheres as medium stress, and potential of -10 atmospheres as severe stress. Sub-factors included four levels of biological fertilizers: No inoculation, seed inoculation with Azotobacter strain, seed inoculation with Mycorrhiza, and concomitant use of Azotobacter + Mycorrhiza. Salicylic acid was also considered at two levels: no foliar application and foliar application with a concentration of 0.6 mM. The following plant characteristics were studied: plant height, root dry weight, shoot dry weight, total chlorophyll content, proline content, percentage, and essential oil yield. At full flowering stage, the plants were harvested and placed in an oven at 75 ° C for 24 hours to measure the dry weight of roots and shoots. 10 g of leaves and flowering twigs from each replicate were transferred to the laboratory to measure physiological traits. SAS 9.4 software was used to perform a two-year combined analysis of variance for the recorded traits. To ensure the uniformity of variance of errors, the Bartlett uniformity test of variance was performed based on the mean squares and the degree of error freedom in two years. Mean traits were also compared using the least significant difference test (LSD) at the 5% probability level. Results and Discussion The results showed that the effect of drought stress, fertilizer and salicylic acid treatments on the studied traits of plant height and shoot and root dry weight, chlorophyll content, percentage and yield of essential oil and proline content were significant. Salicylic acid and the combined application of Azotobacter + mycorrhiza increased plant height, plant dry weight and root, as well as increased chlorophyll content, proline, percentage and yield of safflower essential oil under drought stress. According to the results of this experiment, it can be argued that the response of plant height, plant dry weight and essential oil yield to the increase in drought stress levels was negative, but the root dry weight, total chlorophyll, proline and essential oil percentage were the opposite response. The highest amount of these traits was observed in severe stress conditions and the combined application of bio-fertilizers (Azotobacter + Mycorrhiza) and salicylic acid 0.6 mM had a positive and increasing effect compared to other levels of bio-fertilizer and salicylic acid in The studied traits of the present study were observed. Conclusion According to the results of this experiment, the application of bio-fertilizers and foliar application of salicylic acid causes dehydration and dehydration, as well as the presence of essential oils, nutrients, and the quality of summer safflower under drought stress.