- The use of KNO 3 as a means to reduce salt damage to peanuts (Arachis hypogaea L.) was tested in sprayhydroponics (aeroponics) with 50 mM NaCl and 1, 3, 5, 7, and 9 mM KNO 3. The addition of KNO 3 caused an increase in dry weight of the shoot, root length, chlorophyll content, nitrate reductase activity, and the reduction of salt injury symptoms in the leaves with an optimum at 5–; 7 mM KNO 3. None of these factors was correlated with proline content. Mean root diameter was abnormally thick in low KN03 concentrations and became thinner in higher KNO 3 concentrations, reaching the lowest value at about 6 mM KNO 3. Concentrations of Na+ and CI-in the shoot, but not in the root, decreased with the increase in KNO 3 concentration. It is suggested that K+ and NO 3-inhibited Na+ and CI-translocation from the roots to the shoots so that leaf metabolism was protected against salt damage.