Effects of NACL stress on leaf growth, photosynthesis and ionic contents of strawberry cvs 'Elsanta' and 'Korona'

In a two-year study, strawberry (Fragaria x ananassa Duch.) cvs ‘Elsanta’ and ‘Korona’ showed differences in their sensitivities to salinity as applied by irrigating plants with nutrient solutions with 30 mM or 60 mM NaCl concentration. One month after start of treatments, necrotic symptoms appeared on leaf margins of ‘Elsanta’. ‘Korona’ leaves, however, showed any to few symptoms. During the first growing season, salinity impaired the growth of ‘Elsanta’ leaves as indicated by a reduction in leaf area, leaf expansion rate and dry weight. During the second season, the reduction in leaf growth was more severe. By comparison, growth of ‘Korona’ leaves was reduced only during the second season. Total leaf number was unaffected by salinity in both cultivars; however, the number of dead leaves increased significantly due to salinity in ‘Elsanta’, but remained fairly unchanged in ‘Korona’. Maximum assimilation rates and carboxylation efficiencies, calculated from the A/Ci curves of leaves, were reduced by 39% and 44% in ‘Elsanta’ and by 22% and 34% in ‘Korona’, respectively. The net photosynthetic rate of ‘Elsanta’ was slightly reduced in tendency by salt treatments, while in ‘Korona’ the reduction was significant at the highest salt treatment. Salinity had no effect on the Na+ content in leaves of both cultivars. However, the leaf Cl- content increased with increasing salt level, reaching maximum value in ‘Elsanta’ leaves treated with the highest salt level. This indicates that the effect of salt on leaves was due to Cl-, not to Na+. Root Na+ content increased with salinity in both cultivars. The increase in root Cl- content in ‘Elsanta’ was not significant, but it rose in tendency. Cl- content in ‘Korona’ roots increased significantly with increasing salt level. This suggest that ‘Korona’ strawberry is able to accumulate absorbed Cl- in root tissues, thus preventing the translocation of this toxic ion to the leaves.