Comparative studies on growth and physiological responses to saline and alkaline stresses of foxtail millet (setaria italica L.) and proso millet (panicum miliaceum L.)

Soil salinization and alkalization are widespread environmental problems. To compare the growth and physiological responses under saline stress (SS) and alkaline stress (AS), Foxtail millet (Setaria italic L) and Proso millet (Panicum miliaceum L) were tested under saline and alkaline conditions by mixing the two neutral salts (NaCl and Na 2SO 4) and the two alkaline salts (NaHCO 3 and Na 2CO 3). Compared to SS, AS inhibited in greater extent plant dry weight, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and relative water content (RWC) and the rates of reduction were more pronounced in Foxtail millet, indicating that tolerance to AS was higher in Proso millet than in Foxtail millet. Sodium concentration in leaves was enhanced at double by AS than in SS. Foxtail millet accumulated more Na in the leaves and stem but the roots of Proso millet contained a higher concentration of Na, indicating that Proso millet inhibited the transportation of Na from roots to shoots which resulted in less of a decrease in plant growth. The N content markedly decreased under AS in leaves, stems and roots of both species. The proline content in leaves increased under both treatments and it was higher in SS than in AS. These results suggest that the potential extent of stress-induced injuries was higher in Foxtail millet than in Proso millet and thus Proso millet may have a higher capacity to tolerate saline and alkaline conditions, especially the more deleterious alkaline condition.