Effects of Bio-Regulators on Morphological and Physiological Traits and Essential Oil of Ammi visnaga (L.) Lam

Introduction[1]Ammi visnaga (L.) Lam is a herbaceous medicinal plant and belongs to Umbelliferae family. It is native to the Mediterranean region. A. visnagais well known as a source of essential oil and is especially cultivated for it therapeutic properties (diaphoretic, carminative, antispasmodic, antiseptic, tonic,) being used in traditional medicine systems in many countries. Essential oil of A. visnaga is known for its proprieties against coronary diseases and bronchial asthma. Phenolic compounds considered as a kind of bio-regulators which are synthesized in the environmental conditions in plant cells. These compounds are involved in various processes of plant growth and reproduction as well as a defense mechanism against biotic and abiotic stresses. Amino acids as bio-regulators have been identified as an alternative to chemical fertilizer to increase soil fertility and crop production in sustainable farming. Therefore, the main objective of the present field experiment was to investigate the effects of bio-regulators on morphological and physiological traits and essential oil of A. visnaga. Materials and MethodsA factorial experiment was performed based on a randomized complete block design (RCBD) at Agricultural Research Institute of Zabol University in 2014-15. The experiment was conducted in pots with a height of 20 cm and a diameter of 33 cm. The treatments used in this study consisted phenolic compounds (salicylic acid, trans-cinnamic acid and benzoic acid with three levels of 5, 10 and 20 mg l-1) and amino acids (phenylalanine and tyrosine with three levels of 50, 100 and 200 mg l-1). Distilled water was used as control. All treatments were applied by foliar application and spraying was done 30 days after planting. Measurement was performed at maturity stage (210 days after planting) and fruiting (180 days after planting). The measured traits include vegetative growth characteristics (plant height, branch number, umbel number, fresh weight of herb and dry weight of herb), relative water content (RWC), photosynthetic pigments (Chl a, Chl b, carotinoids, Chl a+Chl b and (Chl a+Chl b)/carotinoids), carbohydrate (total carbohydrates, soluble carbohydrate, insoluble carbohydrate), Fruit yield, essential oil content and yield. For identifying the essential oil components, essential oil fraction was collected and subjected to GC/MS (Gas Chromatography-Mass spectrometry) analysis. Analysis of variance by using SAS software and mean comparisons by Duncan’s multiple range test (at the 5% probability level) was done. Results and DiscussionThe results indicated that bio-regulators significantly affected on all of the traits.  In addition, benzoic acid 20 mg l-1 had the greatest impact compared to other treatments so that, vegetative growth characteristics 46.2 percent, RWC 60.2 percent, photosynthetic pigments include Chl a 77.6, Chl b 60.6, carotinoids 66. 7, Chla+Chl b 73.3 and Chl a+Chl b/carotinoids 19.1percent were increased compared to control treatment. After extraction type and amount of volatile compounds were determined in the aerial part of A. visnaga with GC-MS. Dominant compounds of essential oil in this plant were included 2, 2-dimethylbutanoic acid, isobutyl isobutyrate, thymol and croweacin. In this study, all treatments on the green tissues of A. visnaga were increased the essential oil content. The results of this study demonstrated that, the use of bio-regulators, with aimed at reducing the use of chemical fertilizers, had a positive effect to increase the quality and quantity of A. visnaga and also, sustainable production and environmental protection. ConclusionThe results of this study demonstrated that, the use of bio-regulators, with aimed at reducing the use of chemical fertilizers, had a positive effect to increase the quality and quantity of A. visnaga and also, sustainable production and environmental protection. Considering the importance of the production of medicinal plants in farming systems, bio-regulators such as phenolic compounds seem to be a viable alternative to chemical fertilizers in the production of these plants.