Abstract
DURING the winter season in various parts of Saudi Arabia, temperatures decrease up to 14 degrees C, and water salinity levels are affected by irrigation. The purpose of this study was to investigate the interactive effects of salinity stress and chilling temperature on plant growth, F-v/F-m, chlorophyll content and gas exchange in two forage species, Pennisetum purpureum and Zea mays. The treatments involved daytime/nighttime temperatures of 14/12 degrees C (chilling temperature) and 24/22 degrees C (optimum temperature) and 5 NaCl concentrations (0, 75, 150, 225, 300 mM). The findings showed that NaCl levels were higher and growth parameters and gas exchange of the two species lower at chilling temperature than at the optimum temperature. The optimum temperature did not induce any significant decrease in F-v/F-m values of P. purpureum at the different salinity treatments, while chilling temperature was significantly reduced the F-v/F-m values for both species at higher salinity. The chlorophyll content was higher at 24 degrees C under increased salinity in P. purpureum. In addition, senescence occurred in Z. mays grown at 14 degrees C and salinity concentrations of 225 and 300 mM within three weeks of emergence. The interaction between salinity and chilling temperature significantly affected most measurements of the two species; however, P. purpureum showed high resistance to stress. Therefore, the obtained results will be useful for agricultural application of P. purpureum as a reliable crop for saline lands under chilling temperature conditions.