Nitrogen application improves gas exchange characteristics and chlorophyll fluorescence in maize hybrids under salinity conditions

The understanding of crop physiological responses to salinity stress is of paramount importance for selection of genotypes with improved tolerance to this stress. Maize (Zea mays L.) hybrids Pioneer 32B33 and Dekalb 979 were grown in pots and subjected to three levels of salinity under four nitrogen levels to determine the role of nitrogen under saline conditions. Salinity stress effects on gas exchange characteristics and chlorophyll fluorescence of maize hybrids were evaluated under semi-controlled conditions. Under salinity stress, the changes in the net photosynthetic rate (P (N)), stomatal conductance (g (s)), and transpiration rate (E) were similarly directed: all decreased and were lower than in control at the higher salinity level (10 dS/m). Water use efficiency was increased with increasing salinity since transpiration was stronger depressed by salt than photosynthesis. Plants subjected to the lower level of salinity did not differ from control in tested characteristics. Nitrogen application ameliorated the effects of salinity.