Effects of salinity stress on certain morphological traits and antioxidant enzymes of two Carica papaya cultivars in hydroponic culture

Abstract

Carica papaya L. is the only species belonging to the Carica genus. Salinity stress in soil or water, especially in hot, arid regions, could limit plant growth and reduce its yield. This research studied six-month old seedlings of two cultivars of papaya (‘Sinta’ and ‘Solo’), in solid, disease-free form for two weeks inside a half-dose of Hoagland solution. Results obtained from the effects of salinity stress indicated that the longest root and shoot were observed in the control treatment in ‘Sinta’. Moreover, there was no significant difference between the two cultivars in terms of root length, shoot length, fresh weight of roots and fresh weight of shoots in different salinity levels. The highest dry weights of roots and shoots were found in the ‘Sinta’ control treatment, while the lowest was observed in ‘Solo’ 6 dS/m treatment. There was no significant difference between the two cultivars in terms of dry weights of roots and shoots. Finally, the interaction of salinity levels showed that increasing salinity in both cultivars led to higher peroxidase, catalase, superoxide dismutase and ascorbic peroxides activity. By increasing the salinity level, the total protein and proline greatly increased in both cultivars, where the maximum value was found in the ‘Sinta’ 6 dS/m salinity treatment, and this was significantly different from other treatments. A comparison of the different salinity levels showed that there was a significant difference between the 6 dS/m salinity treatment and other treatments.