Evaluation of quantity and quality of Linum usitatissimum L. fatty acids under the influence of boric acid, salicylic acid, and urea foliar application during the day

Linum usitatissimum L. is one of the most important oilseed crops in the world and moreover, its oil is a valuable source of essential fatty acids composed of omega-3 such as alpha-linolenic acid. This plant is sensitive to fertilizer that is poured near the stem. Therefore, foliar application of nutrients is used as an efficient method with a major impact on the growth, quantity and quality of active ingredients in this product. This factorial experiment was performed based on a randomized complete block design with three replications in the Medicinal Plants Research Farm of Islamic Azad University, Miyaneh Branch, during 2019 to assess  the effect of foliar application of different concentrations of boric acid, salicylic acid and urea at different hours of the day on increasing the quantity and quality of essential fatty acids. Treatments were applied at ten-day intervals in three periods after the beginning of flowering and the final harvest was performed to extract the oil with N-hexane solvent after capsule maturity. The percentage of fatty acid profile of flaxseed oil were determined using GC and GC-MS connected to mass spectrometer. Based on the results, the foliar application 50 mg/l salicylic acid on the percentage of alpha-linolenic acid and 3 liters of boric acid on linoleic acid after sunset, and 100 mg/l salicylic acid on eicosadienoic acid before sunrise and 5 g/l urea on palmitoleic acid after sunset were effective. Therefore, a combination of environmental effects on the plant before and during foliar application and plant physiology during and after uptake determines the effect of foliar application.