Abstract

In drought stress conditions, the imbalance between energy intake and consumption by photosynthetic organ causes the production of reactive oxygen species (ROS) and inability of the plant to control them, which eventually led to stress in the cell membranes and incidence of symptoms caused by oxidative damage. Antioxidant enzymes are considered as the fastest units that fight against reactive oxygen species. In this study, the changes in catalase and peroxidase activities in two levels of drought stress conditions (drought stress and control) and its effect on cell membrane and chlorophyll stability in the tolerant (Unknown 11, HomaandOhadi), semi-tolerant (Sabalan and Rasad( and sensitive (SARA-PBWYT-85-86-22-5 and SHARK-4-0YC-0YC-0YC-5YC-0YC) lines of wheat were analyzed in a factorial experiment based on randomized complete blocks with three replicates. The drought stress caused increase in the peroxidase enzyme activity of Unknown 11, Ohadi and Rasad lines. Although, no increase in peroxidase enzyme activity was shown, Homa still had the highest rate of enzyme activity in drought and control conditions. The activity of catalase enzyme in stress condition in all investigated lines remained stable or decreased and there was no specific relation between the activity of the enzyme and drought resistant. The highest index of chlorophyll stability in the stress condition was perceived in lines HomaØŒOhadi and Unknown 11. Also, the most stabilized and the most inconstant cell membrane in stress condition was related to lines Rasad, Homa and SARA-PBWYT-85-86-22-5. In drought condition, there was a positive correlation between peroxidase enzyme activity, yield and stability of chlorophyll b, whereas we did not perceive any positive correlation between catalase enzyme activity and yield. Moreover, considering the existence of a negative correlation between peroxidase enzyme activity and cell membrane stability, it can be concluded that more activity of peroxidase enzyme in drought stress condition leads to increased cell membrane and chlorophyll stability, and it is related to the drought resistance of different lines.

Key words: Wheat lines, catalase, peroxidase, cell membrane stability, chlorophyll stability index.