The purpose of this study was to investigate the allelopathic effects of Achillea santolina L. shoot aqueous extract on dry weight and photosynthetic pigment contents as well as some metabolic and biochemical processes during germination of wheat plant (Triticum aestivum L. Sakha 93). To exclude the involvement of osmotic stress in plant reaction to phytotoxic compounds, the study compared the effect of 0.5%, 1%, 2%, 4%, and 8% (w/v) Achillea shoot aqueous extracts with distilled water as a control. Most of measured parameters of wheat plant exhibited a great sensitivity to Achillea extract. Germination, shoot and root length, dry weight, water content, chlorophyll content, proteins, carbohydrates and proline were significantly inhibited by increasing the concentration of allelochemicals extracted from Achillea. Achillea extracts enhanced the production of hydrogen peroxide (H2O2), electrolyte leakage (EC), and malondialdeyde (MDA) in wheat plant. The activities of antioxidant enzymes (such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione peroxidase (GPX)) beside the contents of non-enzymatic antioxidants as ascorbic acid and glutathione (AsA & GSH) were markedly affected after treatment with Achillea extract. The allelopathic effects of Achillea on growth alongside with metabolic and biochemical performance of wheat plant is mostly due to the allelochemicals extracted from its shoots.
Key words: Phytotoxicity, Achillea santolina, Oxidative stress, Triticum aestivum L.,Lipid peroxidation, hydrogen peroxide, Electrolyte leakage, Membrane permeability, Antioxidant enzymes,non enzymatic antioxidants.
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