Drought stress is one of the most important factors limiting the survival and growth of plants in different habitats of Egypt. This study was carried out to investigate the effect of drought stress on growth and some metabolic activities of sunflower seedlings under treatments with ascorbic acid (AsA) or CaCl2. Drought stress showed a marked reduction in shoot length, leaf area, shoot fresh and dry weight, photosynthetic pigments, soluble sugar, and amylase activity. On the other hand, root length, soluble proteins, protease activity, proline content, soluble phenolics and flavonoid contents, phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO) activities, H2O2 and Malondialdehyde (MDA) contents, and total antioxidant capacity were induced compared with normal plant. The application of AsA or CaCl2 mitigated the drought stress throughout the increase of growth criteria, antioxidant enzymes and photosynthetic pigments and decreased of H2O2, Malondialdehyde (MDA), soluble phenolics and flavonoid contents.
Key words: Antioxidant enzymes; Ascorbic acid; CaCl2; Drought; Photosynthetic pigments; Sunflower
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