Exogenous application of KNO₃ elevates the salinity tolerance of Stevia rebaudiana through ion homeostasis mechanism

Abstract

Number of tables: 05Number of figures: 07 (5, 6, 7 will be colour online-only) Number of Words (start of the introduction to the end of the acknowledgements): 6502Supplementary data: two tables (Table S1 and S2) and one figure ( Fig S1) Exogenous application of KNO 3 elevates the salinity tolerance of Stevia rebaudiana through ion homeostasis mechanism HighlightThe detrimental effects of moderate and higher salinity levels on growth and dry leaf yield of stevia were observed. However, tolerance level can be elevated through exogenous application of KNO 3 . Abstract Though relatively little is understood of adaptation, physiological and metabolic changes ofStevia rebaudiana under exposure to salinity stress, it is hypothesized that exogenous application of potassium (K + ) could elevates the salinity tolerance through ions homeostasis.Thus, an experiment was conducted with twenty treatment combinations comprising four salinity levels (irrigation with normal water as control and three level of NaCl at 40, 80 and 120 mM) and five different concentrations of KNO 3 (0.0, 2.5, 5.0, 7.5, and 10.0 g L -1 ). Dry leaf yield was not negatively affected with mild salinity (40 mM). However, the detrimental effects were observed at moderate and higher salinity levels (80 and 120 mM). The uptakes of K + , Ca 2+ , and N were significantly reduced at higher salinity level, whereas accumulations of Na + and Cl − ions in plant tissues were substantially increased. Proline content in leaf was also increased significantly (P≤0.05) in response to salt stress. Among the foliar application, KNO 3 at 5.0 gL -1 registered significantly (P≤0.05) higher dry leaf yield compared with control. Exogenous application of K+ under moderate salinity stress maintained ion balance in cytosol, particularly K: Na. Thus, the salinity tolerance of stevia can be elevated to some extent through exogenous application of K + .