Foliar application of L-phenylalanine, sodium selenate, and nitroxine biological fertilizer can improve antioxidant and phytochemical properties of goji berry (Lycium barbarum L.)

Purpose: Lycium barbarum berries can be a source of natural antioxidants for human food production. Research method: To increase the antioxidant activity of secondary metabolites in goji berry seedlings, we applied amino acid L-phenylalanine (Phe: 0.5, 1, and 1.5 mM), sodium selenate (Se: 0.25, 0.5, and 1 mg. L-1), and nitroxine biological fertilizer (170, 330, and 500 μL.L-1) at three levels. Distilled water was the control treatment. The experiment took place at the research farm of Ferdowsi University of Mashhad during 2021-2022. Findings: The results revealed that the treatments significantly affected goji berry plants regarding physiological and chemical attributes. Phenylalanine, selenium, and nitroxine substantially affected photosynthetic pigments, including chlorophyll and carotenoid, antioxidant, and catalase during the two years of foliar application. The results showed that phenylalanine with selenium increased the amounts of flavonoids, anthocyanins, and carbohydrates in goji berry plants. Applying phenylalanine alone had a positive, more potent effect on the amount of phenylalanine ammonia-lyase enzyme, which shows the impact of this substance on the phenylpropanoid pathway. Using it with nitroxine enhanced the phenol content and superoxide dismutase activity significantly. Research limitations: There was no limitation. Originality/Value: According to the results of this experiment, during the two years of 2021 and 2022, phenylalanine improved antioxidant enzyme activity and other traits significantly. Using phenylalanine and sodium selenate at low concentrations increased all antioxidant compounds and improved plant growth.