Comparison between of Photosynthetic Pigments, Osmotic Regulators and Antioxidant Enzymes of Nimroz and Nomar Barley Cultivars of Sistan Region under Drought Stress

Drought is one of the most important stresses that inhibit growth of plants and due to mainly disturbance of the balance between the production of reactive oxygen species and antioxidant defense, causes oxidative stress and different biochemical and physiological responses in plants. So, the evaluation of plants for drought tolerance to cultivate in dry regions is very important.In this way, the present study aimed to investigate and compare two native barley cultivars of Sistan region (Nimroz and Nomar) based on measurement of some defense mechanisms and physiological properties including Antioxidant enzymes activity (Catalase (CAT), Ascorbate Peroxidase (APX), Polyphenol oxidase (PPO)) photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll and carotenoids), protein content, relative leaf water content (RWC) and some Osmotic regulators (proline and carbohydrate) were under drought stress. This experiment was performed as a factorial in a completely randomized design with three replications, conducted at the Institute for Biotechnological Research in the University of Zabol. Experimental treatments included drought stress (50%, 75% and 100% of the field capacity (control)) and two cultivars native to Sistan region (Nimroz and Nomar). Analysis of variance showed that the effect of cultivar, drought stress and interaction of cultivar and drought stress were significant at 1% probability levels, on all studied traits. Results indicated that with increasing drought stress levels compared to normal levels, the amount of photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll and carotenoids), protein content and relative leaf water content (RWC) decreased. However, proline and carbohydrate concentration, carotenoid content, the activity of antioxidant enzymes CAT, PPO and APX were increased. Based on the results of the interaction, it was identified that Nimroz cultivar had a better reaction than Nomar cultivar in terms of protein, relative leaf water content, carotenoids, osmotic regulators and antioxidant enzymes (catalase and ascorbate peroxidase) during drought stress. While the Nomar cultivar was the highest average in terms of chlorophyll a, chlorophyll b, total chlorophyll, protein and enzyme polyphenol oxidase compared to the Nimroz cultivar during drought stress.