The Role of Potassium Nitrate in Physiological Parameters of Citrus aurantium Seedlings Exposed to Salinity

摘要

A hydroponic experiment was carried out under control growth conditions to investigate the impact of KNO_3 on the physiology of Citrus aurantium L. seedlings exposed to salinity. Treatments were: (i) Control, plants receiving nutrient solution without NaCl, (ii) Salinity treatment, as for control plus 50 mM NaCl. The salinity treatment was combined with supplementary KNO_3 at three concentrations (5, 10 or 20 mM KNO_3). Data indicate that the salt treatment (50 mM NaCl) led to significant decreases in photosynthetic rate, stomatal density and total chlorophyll content, accompanied by decreases in leaf K~+/Na~+ ratio. However, carbohydrates and proline content were unaffected in the leaves of NaCl-treated plants. Supplementary 20 mM KNO_3 significantly ameliorated the adverse effects of salinity on chlorophyll content. However, exogenously applied KNO_3 does not measurably affect photosynthetic rate, stomatal density, carbohydrates content and K~+/Na~+ ratio compared to NaCl exposure. Additionally, content of total phenols was reduced by external KNO_3 applications whereas proline content was suppressed by 10 mM KNO_3 application. These observations suggest that KNO_3 has a negative impact on phenol biosynthesis under salinity conditions.