Enhancement of nitrate reduction by chlorine application inSuaeda salsa(L.) Pall

We have previously reported that one of the mechanisms of growth stimulation of the halophyte Suaeda salsa (L.) Pall by NaCl is partly attributed to increased activity of photosystem II by Cl application. In the present study, the effect of Na and/or Cl application on the reduction and assimilation of nitrate in S. salsa was examined by growing plants in nutrient solutions with the following four treatments: –Na·–Cl, +Na·–Cl, –Na·+Cl and +Na·+Cl at 5 mol m−3. Growth was stimulated by the application of Cl, but not Na. The total amount of nitrogen absorbed did not differ among treatments. However, nitrate accumulation in the plant, particularly in the stem, was much higher in the –Na·–Cl and +Na·–Cl treatments than in the –Na·+Cl and +Na·+Cl treatments. In contrast, the accumulation of crude protein in all plant tissues and of amino acids in the leaves was higher in the –Na·+Cl and +Na·+Cl treatments than in the –Na·–Cl and +Na·–Cl treatments. Thus, nitrate reduction and assimilation were stimulated by Cl application, irrespective of Na application. Increased nitrate reduction was considered to be the main cause of the increased nitrate assimilation induced by Cl. Mechanisms of stimulation of nitrate reduction and assimilation are discussed.