EXOGENOUS APPLICATION OF POTASSIUM NITRATE TO ALLEVIATE SALT STRESS IN RICE SEEDLINGS

Abstract

□ Overall growth characteristics of many plant species cultivated in soil affected by salinity could be alleviated by the application of potassium nitrate (KNO₃) to the soil. The aim of this research was to investigate salt-tolerance in a salt-sensitive rice cultivar, ‘Pathumthani 1’ (PT1), in response to the exogenous application of 11.8 mM KNO₃, in comparison to ‘Homjan’ (HJ), a salt tolerant cultivar. Water potential (ψ_w) in both the roots and leaves of PT1 seedlings under salt stress dropped significantly, while it was maintained in PT1 pretreated with KNO₃, and similarly in HJ. The reduction of leaf water potential was positively related to total chlorophyll degradation, leading to diminished chlorophyll fluorescence, directly affecting growth in plants exposed to salt stress. In salt-sensitive PT1, the application of 11.8 mM KNO₃ improved salt-tolerance via the conservation of water use efficiency, the maintenance of photosynthetic pigments, enhancement of chlorophyll a fluorescence, and stimulation of growth characters.

Keywords:

• chlorophyll a fluorescence
• osmolarity
• pigments
• salt tolerance
• sodium chloride

ACKNOWLEDGMENTS

This research was supported by the National Center for Genetic Engineering and Biotechnology (BIOTEC; Grant number BT-B-02-RG-BC-4905) and partially supported by the Thailand Graduate Institute of Science and Technology (TGIST; Grant number TGIST 01-48-041), National Science and Technology Development Agency (NSTDA).