Physiological, biochemical, and functional changes in quinoa (Chenopodium quinoa Willd) under potassium and zinc applications in drought stress conditions

The utilization of chelated fertilizers at specific concentrations could serve as an efficient method to mitigate the effects of drought stress in plants, considering it a global climatic issue. The objective of this study was to ascertain the influence of potassium and zinc chelate fertilizers on improving drought tolerance in quinoa plants. The experiment was conducted over two cropping years, 2018-2019 and 2019-2020. It followed a split-plot factorial design within a randomized complete block layout, in three replicates. The results indicated that the foliar application of the combined treatment of 50K + 50Zn significantly increased grain yield, particularly in the Q26 cultivar, under drought-stress conditions. However, the best harvest index was related to the Q26 cultivar under 100Zn application conditions. Nevertheless, the application of chelated fertilizers significantly enhanced these traits under stress compared to the non-application conditions. Furthermore, the content of glycine betaine and proline in the plant increased under the influence of 100K and 100Zn applications in the Q29 cultivar in 25% FC. Based on the obtained results for Catalase enzyme activity at 25% FC and in the presence of 100Zn foliar application and for Peroxidase at 25% FC and the presence of the combined 50K + 50Zn foliar application in the Q29 cultivar, the highest activity of these enzymes was observed. Consequently, considering the increased contents of glycine betaine and proline in the foliar application, as well as the enhanced activity of antioxidant enzymes contributing to improved drought tolerance in these plants, the application of potassium and zinc chelates as fertilizers is recommended.