1National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
2Department of Botany, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.
Potassium is a major nutrient which may play an important role in many processes such as ion homeostasis in plant cells and osmotic adjustment of guard cells during stomatal opening and closing. Pathumthani 1 (PT1) rice has been reported as being a salt sensitive cultivar and has been selected as a model plant in this study to investigate the possibility of improving the osmotic potential, pigment stabilization, photosynthetic efficiency and growth characteristics of this plant under salinity stress by potassium nitrate (KNO3) application. Sodium ion accumulation in root and leaves of KNO3 (11.8 mM) treated plants declined as compared to the control plants. In control plants, however, due to decline in potassium ion content, the Na+ / K+ ratio increased significantly. A positive relation between Na+ accumulation and osmotic potential was found. Osmotic potential (Ys) in the root and leaf tissues of PT1 rice treated with 11.8 mM KNO3 was maintained at low levels, which was accompanied with the stabilization of photosynthetic pigments, high photosynthetic performance and better growth characters under 200 mM NaCl. The photosynthetic ability in plants with KNO3 application was positively related to plant dry weight. Exogenous KNO3 application to rice crops may play a vital role as a short-gun technique for the improvement of salt tolerance.