Evaluation of Biochemical Parameters and Antioxidant Activity of Ocimum basilicum L. in Response to Vermicompost and Copper Sulfate

Introduction  Basil (Ocimum basilicum L.) is an annual and herbaceous plant of the family of Lamiaceae. It is used as an antispasmodic, appetizer, carminative, diuretic, lactation aid, and sedative in traditional medicine. In general, basil is rich in phenols and flavonoids. Organic and chemical fertilizers are necessary for each other and both types of fertilizers are needed to create favorable conditions to improve biochemical traits. Overuse of chemical fertilizers has caused several problems in agriculture including changes in the soil structure, contamination of underground waters, and heavy metal toxicity. Agricultural scientists suggest replacing chemical fertilizers with organic products to reduce negative effects on environment and soil properties. In recent years, neglecting the importance of organic matters to improve soil fertility has led to an increase in chemical fertilizer use in Iran. Organic matters due to their positive effects on soil are identified as one of the important pillars of soil productivity. However, more than 60 percent of agricultural soils in Iran contain less than one percent of organic matter. Therefore, the objective of this study was to investigate the influence of vermicompost and copper sulfate on biochemical parameters and the antioxidant activity of basil. Materials and Methods  To investigate the effect of vermicompost and copper sulfate on the biochemical characteristics of Basil's medicinal plant, a factorial experiment was conducted based on randomized complete block design with a field experiment at the Faculty of Agriculture, University of Birjand. The factors included vermicompost in three levels (0, 5, and 10 t.ha-1) and copper sulfate in three levels (0, 3, and 6 per thousand) with three replications. After applying the treatments and after the plants entered the flowering stage, ten plants from each plot were randomly selected taking into account the marginal effects and then samples of the developed leaves of 10 plants were randomly prepared and the biochemical traits of basil were measured. Measured traits included photosynthetic pigments, antioxidants, phenols, anthocyanins, flavonoids, total sugar, and biological function. Statistical analysis of data was performed using SAS statistical software. Results and Discussion  The results of the mean comparison showed that vermicompost had a significant effect on chlorophyll content, antioxidant activity, anthocyanin, flavonoids, sugar, and biological function of basil so that the highest amount of flavonoids (3.26 mg.g-1) with the application of 10 t.ha-1 of vermicompost and the lowest Its amount (2.65 mg.g-1) was obtained from the control. Treatment of 10 t.ha-1 of vermicompost increased plant sugar by 37.05% compared to the control. Copper sulfate also affected chlorophyll a and total, antioxidant activity, phenol, anthocyanin content, sugar, and biological function, so that the highest activity of phenol and sugar (15.29 and 12.99 mg.g-1, respectively) of the treatment of 3 per thousand Copper sulfate and its lowest levels (10.98 and 9.19 mg.g-1, respectively) were obtained from the control. The results of interactions also showed the highest levels of chlorophyll a (1.62 mg.g-1), chlorophyll b (2.57 mg.g-1), total chlorophyll (4.19 mg.g-1), antioxidant activity (92.57%), and anthocyanins (3.03 mg.g-1) was obtained by applying 10 tons per hectare of vermicompost and 3 per thousand of copper sulfate. Furthermore, the highest increase in biological function (20968.3 kg.ha-1) with the application of 5 t.ha-1 of vermicompost and 6 per thousand copper and the lowest (16596.7 kg.ha-1) was related to the control. Conclusion  In general, the results indicated a positive effect of vermicompost and copper sulfate on Basil's biochemical characteristics. Therefore, vermicompost (10 t.ha-1) of and copper sulfate (3 per thousand) treatments can be suggested as a suitable treatment. From the present study, it can be concluded that the combined application of organic fertilizers with chemical fertilizers has a useful and effective role in improving photosynthetic pigments, antioxidants, anthocyanins, and the biological function of basil. In the discussion of basil production as a medicinal and vegetable plant, the best results in terms of crop production were related to the combined treatments of organic and chemical fertilizers, because these treatments have increased the production relative to organic treatments alone.