Document Type : Research Article
Author
Research Center of Nutrition and Organic Products (R.C.N.O.P), Shahrekord Branch, Islamic Azad University, Shahrekord, Iran
Abstract
Introduction
Satureja bachtiarica is one of the important endemic species and uses in medicinal and food industries. This plant is rich in essential oil, flavonoids, monoterpene glycosides, trypanocidal terpenoids. The main compounds of the essential oil from S.bachtiarica L. collected from natural habitats are alpha-pinene, p-cymene, carvacrol and gamma-terpinene. The environmental factors cause changes in the growth, quantity, and quality of active substances (such as alkaloids, glycosides, steroids and volatile oils) in the medicinal and aromatic plants. Among environmental stresses, water deficit stress plays an important role in the biosynthesis of secondary metabolites in medicinal and aromatic plants in arid and semi-arid regions like Iran. Drought stress has detrimental effects on growth and yield and can upset the balance between the antioxidant defense system and free radicals by stimulating a series of biochemical reactions, where free radicals cause cell damage. In sustainable production systems of medicinal and aromatic plants, stable quantitative and qualitative functions can be achieved under conditions of environmental stress and it is possible to improve the production of secondary metabolites in these plants under adverse environmental conditions. Therefore, this study was done to evaluate the amino acids on the physiological and phytochemical properties of S.bachtiarica to determine and introduce the best amino acids under water stress.
Materials and Methods
This investigation was done from spring (May) 2022 to fall (September) 2023 at the Research Farm (latitude. 32°20′ N, longitude. 50°51′ E, altitude. 2061 m). Based on the Köppen climate classification, the climate of the area of study is classified as cold and semiarid. This study was conducted in a randomized complete block design (RCBD) in split plot layout with three replications. Irrigation regimes (3, 6, 9 day interval) in main plots and foliar application of amino acids (methionine, lysine, phenylalanine and proline) in sub plots were done. In each year, treatments were applied in 3 stage (3 months after sowing, end of vegetation, before flowering, beginning of flowering and early flowering) and harvesting were done in complete flowering. Weed control was done manually during the entire experiment. During the experiment, no fertilizer and no systemic pesticide and herbicide were used. The harvested shoots were transferred to laboratory for extracting and analysis the leaves and stems of treated plants. For assessment of the total chlorophyll content of S.bachtiarica, the leaves were extracted by 80% acetone. The absorbance of the extraction was read at 470, 648, and 664 nm, and the content of total chlorophyll was calculated as mg per g leaf dry weight. Total phenol content was measured by the Folin-Ciocalteu reagent as reported by Singleton and Rossi. The total phenol content was expressed as mg of gallic acid equivalent per g leaf dry weight according to standard curves of gallic acid. The essential oils were extracted by hydro-distillation and analyzed using GC/MS.
Results and Discussion
Applied amino acids significantly influenced the morpho-physiological and phytochemical characters of Satureja bachtiarica. In two years, the highest chlorophyll content (1.41-1.54 mg.g-1FW) and total phenol content (2.45-2.72 mg.g-1FW) were obtained in methionine (2.5 g.l-1) and phenylalanine (100 µM) treatments by irrigation regimes 3 day interval. The highest essential oil contents (1.09-1.61 %) were obtained from the plants treated by methionine (2.5 g.l-1) and phenylalanine (100 µM) treatments by irrigation regime 3 day interval. The main chemical compounds of essential oil were P-cymene (17.12-19.45 %), gamma-terpinene (18.14-16.87 %) and Carvacrol (45.12-51.24 %) belong of cyclic monoterpenes. The treatments had significant effectiveness on cyclic monoterpens such as alpha-terpinene, gamma-terpinene, germacren-d, carvacrol, thymol and p-cymene. Increasing of essential oil content/composition by use of amino acids was seen. The main components of essential oil in plants treated by proline lesser than other treated plants. In two years of this research amino acids of methionine and phenylalanine mad the most amounts of carvacrol and essential oil content. The monoterpene alcohols in volatile oils of the treated plants with amino acids elicitors considerably were higher than the sesquiterpenes. According to ratio of monoterpenes alcohol to sesquiterpenes in volatile oils of the treated S.bachtiarica with different elicitors, the foliar application of amino acids can improve the odor quality of S.bachtiarica volatile oil.
Conclusion
Foliar application of methionine (2.5 g.l-1) and phenylalanine (100 µM) treatments better than other treatments increased the morpho-physiological and essential oil attributes. Environmental condition plays such as drought is a key role in plant growth and biosynthesis of different metabolic compounds. The observed variation in shoot yield and phytochemical content of S.bachtiarica during the studied years may related to differences in photoperiod, temperature, solar radiation, precipitation and occurrence of biotic and abiotic stresses at different growing seasons. Also amino acids had very important effectiveness on content/composition of essential oil of S.bachtiarica. Generally, treats of methionine and phenylalanine can be a good strategy to improve morpho-physiological characters and essential oil quantity and quality of S.bachtiarica in same climate.
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