The Effect of Fulvic Acid and Triacantanol Foliar Application on some Biochemical and Physiological Properties and Active Ingredients of Calendula officinalis

Introduction  Marigold (Calendula officinalis) is an herbaceous plant belonging to the family Asteraceae. C. officinalis is always one of the most widely used medicinal plants and is widely cultivated for its extract in traditional and herbal medicine especially in Iran. Marigold extract has medicinal effects such as wound healing, anti-inflammatory, antibacterial, immune stimulating, anti-tumor and anti-AIDS. To achieve the higher yield and quality in this plant, it’s necessary to have enough nutrition. Fulvic acid stimulates plant metabolism, increases enzyme activity as a catalyst in plant respiration, and increases nutrient efficiency and cell pore permeability. On the other hand, triacanthanol is a type of alcohol with a 30-carbon chain and is found naturally in plant epicotyledonous waxes. The use of triacanthanol increases plant dry weight and reduces the content of sugar, amino acids and protein.  Materials and Methods In order to evaluate the effect of fulvic acid and triacantanol and their interactions on some characteristics of C. officinalis, a factorial experiment with 16 treatments and 3 replications was conducted at greenhouse. Experimental treatments consisted of four levels of fulvic acid (0, 0.5, 1, 2 mg / l) as the first factor and four levels of triacantanol (0, 10-5, 5.5×10-4, 10-4 M) as the second factor. Treatments were sprayed on the plant three times in the form of foliar spray. Physiological factors were measured during the growing season and after applying the treatments. Finally, at the end of the growing season, plants were sampled to measure the parameters. Yield and fresh and dry weight (at flowering stage and in the form of fully opened flowers), shoot height with a ruler, number of leaves and leaf area were measured with a leaf gauge. Number of flowers by counting the number of flowers from the time of the first flower to the end of the experiment without taking into account the unopened buds, the time required for flowering (early flowering, late flowering) in terms of days by noting the date of the day At the time of emergence, the first flower in each treatment was examined. Acetone at 100% was used to measure photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll and carotenoids) and their absorption was measured at 470, 644.8 and 661.6 nm by spectrophotemeter. The measurement of total phenol was performed using a covalent folate reagent in the absorption spectrum of 765 nm in a spectrophotometer. The flavonoid content of all extracts was measured by aluminum chloride colorimetric method. The absorbance of the samples was read at 415 nm by spectrophotometer. Quercetin was used as the standard to obtain the calibration curve. The flavonoid content of the samples was reported as mg quercetin per 100 g fresh plant weight. DPPH free radical scavenger was used to measure antioxidant activity. The absorbance of the samples was read at 517 nm using a spectrophotometer. Results and Discussion Based on the results of this study, it was observed that the foliar application of 10-4 M triacantanol led to an increase in flower yield, leaf area, fresh weight, dry weight, number of flowers, flower height, antioxidant activity, and flavonoid content. On the other hand, the application of 10-5 M triacantanol increased the percentage of evergreen dry matter and phenol content more than the other concentrations. Among the different concentrations of fulvic acid tested, the concentration of 2 mg/l showed the greatest positive impact on the number of leaves, leaf area, fresh weight, dry weight, dry matter percentage, antioxidant activity, and total flavonoid content. Overall, the application of 10-4 M triacantanol and 2 mg/l fulvic acid as a leaf treatment significantly improved most of the measured traits in comparison to the control treatment. It is worth noting that plants treated with 2 mg/l fulvic acid flowered later than the other treatments, and there was a significant interaction between triacanthanol and fulvic acid on flower yield and height. Conclusion  The results of this study in response to the use of the triacantanol and fulvic acid indicate that the use of these two compounds in foliar spraying can be very useful to achieve sustainable production and achieve organic farming. Triacanthanol promotes growth by regulating many of the genes involved in photosynthesis The use of fulvic acid increases the permeability of the cell membrane and better penetration of nutrients from the membrane. Also, soil permeability to nitrogen uptake increases by plant roots.