The Symbiotic Influence of Effective Microorganisms on Biochemical and Morphological Characteristics of Savory (Satureja hortensis L.) under Salinity Stress

Savory plant (Satureja hortensis ) belongs to mints family (Lamiaceae). Environmental and abiotic stresses affect the agricultural plants growth and yield in many regions of the world. Salinity is one of the most limiting factors for growth and production of crops in arid and semiarid regions. Soil salinity is a dominant issue for the sustainability of agricultural production. Reduction of vegetative growth, dry weight and cells mass are some of most common adverse effects of salinity. Salinity increases energy consumption to remove excess sodium ions accumulated in the root cells leading to significant reduction in plant growth rate. Nowadays, effective microorganisms (EM) is one of the biological fertilizers which has attracted a lot of attention as a useful tool to increase plant productivity and stress tolerance rate. The micro-organisms existed in EM improve the health and yield performance of agricultural plants by increasing photosynthesis rate, producing biologically active compounds such as hormones and enzymes, controlling soil diseases and accelerating the decomposition of organic matter in the soil. Therefore, the use of EM bio-fertilizer under conditions of environmental limiting factors such as salinity could be highly important to develop horticultural plant cultivation in regions with saline soli or saline water resources. The purpose of the current study was to investigate the morphological and bio-chemical responses of the savory plant to salt stress, and using EM bio-fertilizer to reduce the adverse effects of salt stress.           

In order to investigate the effect of EM bio-fertilizer on the morphological and bio-chemical characteristics of the savory plant under salinity conditions, a factorial experiment was conducted based on randomized complete blocks design with 4 replications at the Faculty of Agriculture, University of Mohaghegh Ardabili, during 2021. In this study, Em treatments were applied at three levels including 0 (control), 1 and 2 %, and salinity was induced at three levels including 0 (control), 6 and 12 dS/m NaCl. Fresh and dry yield of plants and fresh and dry weight of the roots were measured with a digital scale. The content of chlorophyll a and b, and total chlorophyll were measured by a spectrophotometric method. Proline, soluble sugars and total protein were measured as physiological characteristics.

The results showed that the highest height (30.66 cm) was recorded in plants treated with EM 2 % and grown under control condition. The height of plants decreased with increasing salinity level. Also, the highest fresh and dry yield, and fresh and dry weight of root were obtained by applying EM 2 % under control level of salinity. The highest number of leaves was counted in plants treated with EM 2 %, and grown under control level of salinity. The lowest leaf number was related to non-treated plants grown under salinity level of 12 dS/m. The highest recorded contents of chlorophyll a, b and total were 3.11, 1.85 and 4.96 mg/g FW, respectively. The lowest value of these traits (1.14, 0.65, and 1.79 mg/g FW) was recorded in non-treated plants grown under highest level of salinity. Generally, the amount of chlorophyll a, b and total decreased with increasing salinity level, while EM increased the values of these traits. The results showed that the highest amount of soluble proteins was obtained at control level of salinity and application of EM 2 %, with an average of 38.03 mg/g FW, while the lowest value (15.30 mg/g FW) was obtained in non-treated plants under salinity level of 12 dS/m. The amount of soluble sugars increased with increasing stress level. The highest amount of proline (35.4 μmol/g FW) was obtained under salinity level of 12 dS/m. EM increased the content of photosynthetic pigment under salinity conditions which led to increase photosynthetic performance of treated plants. Also, accumulation of proline as osmoprotectant agent in cells of treated plant, definitely led to decrease the activity of reactive oxygen species resulting in lower damages to cells membrane.

In conclusion, results showed that savory plants fed with EM bio-fertilizer had better growth and yield under salinity conditions than the unfed plants. These plants showed more tolerance rate against salt stress due to better absorption rate and physiological responses. So that the highest values of vegetative traits were recorded in plants treated with EM 2 %. Therefore, this treatment could be recommendable to overcome adverse effects of salinity on savory plants characteristics.