بهرخ دایی حسنی

Vanadium (V) is a transition metal consistently distributed in the Earth’s crust. At trace concentrations, it has been described as a beneficial element for some organisms; however, it is toxic at higher concentrations. This study was conducted hydroponically in a complete randomized design to investigate effects of V (0, 3.25, 7.5, and 15 mg L-1) on antioxidant system of sunflower. Results showed that all applied concentrations of V significantly decreased the plant growth, but increased the free amino acids, proline, malondialdehyde and H2O2 contents of plants. The antioxidant enzymes activities increased in response to the increase in V concentration. The activity of (Guaiacol) peroxidase showed a significant increase at 15 mg L-1 V while the activities of catalase, glutathione reductase, and ascorbate peroxidase decreased significantly by application of V. There was a slight increase in the superoxide dismutase activity at different concentrations of V. The study concludes that the applied concentrations of V induced oxidative stress in sunflower and (Guaiacol) peroxidase was a more effective antioxidant enzyme in scavenging the free radicals in this plant.

Ultraviolet radiation as one of important stressful environmental factors, has deleterious effects on plant physiological processes and growth. Plants confront with this conditions that produce ROS, via specific physiological mechanisms. This study to investigate the effect of UV-C radiation on the physiological responses in radish (Raphanus sativus L.cv), the plant with one year old and belong to brassicaceae . This experiment was conducted in a randomized complete blocks design with different three varieties of plant radish seeds that cultured hydroponically in green house. After two weeks, seedlings were treated with UV-C for a period of 10 days for 3 minutes / day with daily dose of 12KJ/m2. The results of the evaluation showed that in all studied variations, UV-C lead to reduction in shoot and root dry weight and leaf area. The radiation also reduced the photosynthetic pigments (chlorophyll a, chlorophyll b and total chlorophyll), sugar content and total soluble proteins. The total phenol, total amino acids and UV absorbing compounds such as anthocyanins and flavonoids, were increased under effect of UV-c radiation. By considering to obtained results, we concluded that in the variation of assayed metabolites, UV- C treated red radish plants had highest compatibility than other studied varieties.

Salinity is one of the most severe abiotic stresses in one-half of all irrigated lands, causing negative effects on physiological, biochemical, and molecular responses in plants. Application of chemical fertilizers, particularly phosphorus (P) fertilizers, may reduce harmful effects of salinity. In this study, an investigation was performed on the effects of exogenous application of different levels of phosphorous (0, 40, and 80 mg/kg soil as CaHPO4) on hydrogen peroxide (H2O2) and malondialdehyde (MDA) generation, the content of soluble proteins, and activities of antioxidant enzymes like superoxide dismutase (SOD) and peroxidase (POD), in shoots of two different cultivars of Capsicum annuum L. (cv DS 77-172 and cv Sera) under different concentrations of NaCl (0, 50, and 150 mM). Treatment of salt stressed grown seedling with CaHPO4 increased activity of POD. Under salinity conditions, phosphorous treatment decreased contents of H2O2 and MDA. These results indicate salt-induced deleterious effects in both pepper cultivars alleviated by phosphorous treatment.

Safflower, Carthamus tinctorius L., is a member of Asteraceae, cultivated mainly for itsseed and flower, which are used as edible oil and for medicinal applications. Safflower is aresistant plant to the environmental stresses; therefore scientists use this plant as a modelfor studying the mechanism of plant resistance to the environmental stresses. Antioxidantenzyme system is one of the defense mechanisms that plants use for various environmental stresses. In this study some biochemical properties of catalase, an antioxidant enzyme system, from safflower and it sensivity to azide and cyanide was investigated. Carthamus tinctorious L.cv.IL-111 was grown hydroponically in perlite for 40 days and catalase was extracted from their leaves using phosphate buffer 0.1 M, pH 7.2. Study of pH profile, temperature and different concentration of substrate and inhibitors (azide and cynide) on catalase activity in Safflower and non-denaturant polyacrylamide gel electrophoresis of crude extract, showed that at least two isoenzymes of catalase were present in safflower leaves with optimal pH at 6.5 and 8.5, respectively. Isoenzyme active at pH 8.5 was more resistant to temperature in comparison to isoenzyme active at pH 6.5. Effects of inhibitors (azide and cynide) on catalase activity showed that isoenzyme active at pH 8.5 was more sensitive to both inhibitors (azide: 4.6 fold, and cynide: 2.6 fold) in comparison to isoenzyme active at pH 6.5.