Comparison of Physiological Traits of Two Sweet Pepper Cultivars under Salinity Stress

In order to investigate the effect of salinity on the physiology of two cultivars of green and orange bell peppers, an experiment was conducted at the Isfahan University of Technology, Isfahan, Iran in 2019. The experiment was a factorial experiment in a completely randomized design in the greenhouse, in which treatments included four salinity levels (irrigation with normal water, irrigation with saline 1.5, 4.5, and 6.5 dS/m). Increasing the salinity level increased the activity of the ascorbate peroxidase enzyme in orange bell pepper. The highest amount of activity of this enzyme was achieved in orange cultivar when grown in the presence of 6.5 dS/m saline water. Green bell peppers had a higher starch content than orange bell peppers at all salinity levels. Also, with increasing salinity, the K concentration of roots and shoots and Na concentration of shoots increased compared to the normal water irrigation condition. An increasing trend in proline and phenol concentrations was observed with increasing salinity level. Also, increasing salinity level significantly reduced transpiration, stomatal conductance and CO2 concentration in the sub-stomatal space. With increasing salinity level, the abscisic acid and carotenoids concentrations in the leaves increased. In general, salinity led to adverse effects on an array of the examined physiological attributes of both genotypes, though, orange cultivar seemed to be more tolerant to the saline water, compared to the green pepper.