Reduce the Adverse Effects of Salinity On some Physiological Characteristics of Three Rapeseed (Brassicc napus) Cultivars under Elevated Atmospheric Concentration of Carbon Dioxide

In order to evaluate the effects of atmospheric CO2 concentration increment on rapeseed salinity tolerance، four levels of salinity (0، 5، 10 and 15 dS. m-1) on three cultivars of rapeseed (Okapi، Zarfam، and RGS) at three levels of atmospheric CO2 concentration (350، 700 and 1050 ppm) were studied. The experiment was conducted at the greenhouse of Tarbiat Modares University at 2010 and 2011 crop season. Three levels of CO2 concentrations have been considered as three environments in which two other treatments (salinity and cultivar) carried out in a completely block design in factorial arrangement. Results indicated that photosynthesis rate of canola increased with increasing CO2 Concentration (about three times in 1050ppm) in the air and decreased with increasing salinity (21% in 15 dS. m-1). Three times concentration of CO2 (1050ppm) reduced the impact of salinity on photosynthesis. Elevated CO2 by increasing photosynthesis rate، reducing transpiration and increasing water use efficiency reduced effects of salinity. Water use efficiency was increased with increment concentration of carbon dioxide and decreased with salinity.