Ameliorative Effects of Exogenous Potassium Nitrate on Antioxidant Defense System and Mineral Nutrient Uptake in Radish (Raphanus sativus L.) under Salinity Stress

Soil salinization has become a major issue around theworld inrecent years, as it is one of the consequences of climate change assea levels rise. It is crucial to lessen the severe consequences ofsoil salinization on plants. A pot experiment was conducted to regulatethe physiological and biochemical mechanisms in order to evaluatethe ameliorative effects of potassium nitrate (KNO3) on Raphanus sativus L. genotypes under salt stress.The results from the present study illustrated that the salinity stressinduced a significant decrease in shoot length, root length, shootfresh weight, shoot dry weight, root fresh weight, root dry weight,number of leaves per plant, leaf area chlorophyll-a, chlorophyll-b,total chlorophyll, carotenoid, net photosynthesis, stomatal conductance,and transpiration rate by 43, 67, 41, 21, 34, 28, 74, 91, 50, 41,24, 34, 14, 26, and 67%, respectively, in a 40 day radish while decreasedby 34, 61, 49, 19, 31, 27, 70, 81, 41, 16, 31, 11, 21, and 62%, respectively,in Mino radish. Furthermore, MDA, H2O2 initiation,and EL (%) of two varieties (40 day radish and Mino radish) of R. sativus increased significantly (P < 0.05) by 86, 26, and 72%, respectively, in the roots and alsoincreased by 76, 106, and 38% in the leaves in a 40 day radish, comparedto the untreated plants. The results also elucidated that the contentsof phenolic, flavonoids, ascorbic acid, and anthocyanin in the twovarieties (40 day radish and Mino radish) of R. sativus increased with the exogenous application of KNO3 by 41,43, 24, and 37%, respectively, in the 40 day radish grown under thecontrolled treatments. Results indicated that implementing KNO3 exogenously in the soil increased the activities of antioxidantslike SOD, CAT, POD, and APX by 64, 24, 36, and 84% in the roots andalso increased by 21, 12, 23, and 60% in the leaves of 40 day radishwhile also increased by 42, 13, 18, and 60% in the roots and alsoincreased by 13, 14, 16, and 41% in the leaves in Mino radish, respectively,in comparison to those plants grown without KNO3. We foundthat KNO3 substantially improved plant growth by loweringthe levels of oxidative stress biomarkers, thereby further stimulatingthe antioxidant potential system, which led to an improved nutritionalprofile of both R. sativus L. genotypesunder normal and stressed conditions. The current study would offera deep theoretical foundation for clarifying the physiological andbiochemical mechanisms by which the KNO3 improves salttolerance in R. sativus L. genotypes.