Effect of proline on some physiological and biochemical characteristics of two ‎cultivars of Impatiens walleriana under salt stress

The aim of this study was to investigate the effect of foliar application of proline on some physiological and biochemicalcharacteristics of two cultivars of impatiens under salinity stress. The experiment was a factorial based on a completely randomized design with three replications. The first factor was two cultivars of impatiens (Accent Premium Salmon and Tempo Orange), the second factor was foliar application of proline (0 as control, 5 and 10 mM were applied weekly) and the third factor was salinity stress at four levels (0 as control, 20. 40 and 60 mM sodium chloride were applied as irrigation (90% field capacity) every three day). The results showed that increasing salinity stress significantly reduced fresh and dry weight of leaf, stem, root and total plant, time of flower opening, flower diameter, number of flower, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content and catalase activity, and while significantly increased proline content, activity of peroxidase and ascorbate peroxidase enzymes in both cultivars of impatiens. Exogenous application of 5 and 10 mM proline have mitigated salinity stress effects and caused a significant increase in all of the studied characteristics. The highest activity of catalase and proline content was observed in Salmon cultivar, whereas the highest activity of ascorbate enzyme was observed in Tampo cultivar. In general, the results of this study indicated that all levels of salinity stress had negative effects on growth and yield of both impatiens cultivars, but proline application especially at a concentration of 10 mM reduced the effects of salinity stress and increased plant toleranceto stress.