EFFECTS OF DIFFERENT LEVELS OF FOLIAR ZINC AND APPLICATION TIME ON TOTAL PHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY OF POTATO

Abstract

In this research, it was aimed to determine effects of foliar zinc applications before and after flowering on total phenolic content, antioxidant activity, total sugar, reducing sugar and sucrose of potato tubers. This study was conducted in a randomized complete block design in split-plot layout with three replications. Zinc sulfate solution with increasing doses (0, 0.2, 0.4 and 0.8%) was applied to leaves of potato before and after flowering. The results revealed that the effect of increasing zinc doses and application time was significant on total phenolic content. The highest total phenolic contents were obtained from 0.4% zinc treatment and post-flowering application as 70.33 mg kg(-1) and 59.49 mg kg(-1), respectively. The antioxidant activity of potato tubers reached its maximum in plots receiving 0.4% zinc before flowering, with a significant interaction effect between zinc dose and application time. As a conclusion, foliar application of Zn can noticeably improve total phenolic content, antioxidant activity and sugar content of potato tuber, especially in case foliar zinc application was carried out before flowering.