Salinity tolerance in Triticum aestivum-Lophopyrum elongatum amphiploid and 5E disomic addition line evaluated by NaCl effects on photosynthesis and respiration

Abstract

Effects of NaCl salinity on photosynthesis and respiration were studied in wheat (Triticum aestivum) cv. ‘Chinese Spring’ (abbreviated as CS) and the amphiploid and 5E disomic addition line of CS with wheatgrass (Lophopyrum elongatum), a wild facultative halophyte. Only the amphiploid showed NaCl tolerance based on seedling growth. The net photosynthetic CO2 assimilation measured by the rate of O2 evolution was decreased and chlorophyll a/b ratio increased in CS under the presence of 0.4 M NaCl, but no such changes occurred in the amphiploid and 5E disomic addition line. The amounts of total soluble protein and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) per fresh weight were increased in all the lines, while the relative amount of Rubisco per protein remained unchanged. Rubisco specific activity was inhibited in all the lines but Rubisco activity per fresh weight did not change. The total respiratory electron flow and the flow through the cytochrome pathway were increased in CS under the salinity condition, while no changes occurred in both amphiploid and 5E disomic addition lines. The sustained CO2 assimilation, the stability of the light-harvesting photosystem II complex and the normal level of respiratory electron flow through the cytochrome pathway attested the NaCl tolerance in the amphiploid. A positive effect of chromosome 5 on salinity tolerance was suggested by the stability of the photosystem II complex and the cytochrome pathway under the salinity condition.