جستجوی مقالات مرتبط با کلیدواژه "پراکسیداسیون چربی" در نشریات گروه "زراعت"

The Cultivation of medicinal plants such as Lamiaceae family increasing throughout the world significantly. Peppermint consider as an important species in this family which it’s important is due to menthol in essential oil. In this study the physiological and biochemical responses of peppermint investigated under different levels of irrigation including 100 (as control), 75, 50 and 25 % field capacity (FC) in CRD design with three replications in research greenhouse of Agronomy Department of University of Tehran in 2013. The results of Anova indicated that, irrigation levels had high significant effect (P≤0.01) on H2O2, MDA, CAT, APX, GPX and SOD. While, the effect of irrigation levels was not considerable on soluble sugar content. The highest content of soluble sugar and soluble protein were observed at 50 and 75 % FC, respectively. The highest H2O2 and MDA (59.63 and 16.25 µmol/g) observed at 25% FC with significant difference in respect to other treatments. The highest activity of antioxidant enzymes CAT, APX and GPX detected at 50 % FC and reduced with increasing of drought stress up to 25 % FC. The activity of SOD increased with increasing of the drought stress and reaching it to maximum amount at 25 % FC. These results suggest that peppermint is a sensitive plant and cannot increase its capacity against drought stress.

Environmental stresses trigger a wide variety of plant responses, such as altered gene expression to changes in cellular metabolism and growth. The several plant reactions exist to circumvent the potentially harmful effects caused by light, drought, salinity, pathogen infections and other stresses. a-Tocopherol is the major vitamin E compound found in leaf chloroplasts. This antioxidant deactivates photosynthesis-derived reactive oxygen species and prevents the propagation of lipid peroxidation by scavenging lipid peroxyl radicals in thylakoid membranes. In this study, we used the tabacco plants containing of pBin:At.TC construct that overexpressed the tocopherol cyclase gene. For analysis effect of overexpressed this gene, the transgenic plants were subjected to drought stress and were studied number of physiologic parameters such as, chlorophyls and carotenoid, proline amino acid content, relative water content, membrane permeability, in transgenic and wild type plants in normal and drought stress condition. The results indicated that transgenic plants have increased chlorophyl, proline and relative water content and decreased membrane Permeability in 40 and 60 stress levels, in comparison to wild type plants. Therefore the overexpression of tocopherol cyclase gene in tabacco plants maybe cause increased plant tolerance under drought stress conditions.

Understanding of physiological responses of salt tolerance might be lead to identify main salt tolerance mechanisms and essential approaches for improving grain yield stability, and also to select salt tolerant wheat cultivars. Thus, the effects of salinity were investigated on grain yield and some of the characteristics related to salt tolerance. Six wheat cultivars (Roshan, Kavir, Karchia, Gaspard, Shiraz and Qods) differing in salt tolerance at three salinity levels (0, 100 and 200 mM NaCl) were used in a pot experiment, using a factorial experiment based on a randomized complete block design with three replications. Salt stress caused to decrease grain yield, biomass production, chlorophyll content, and catalase activity, while it caused to increase the activity of peroxidase, ascorbate peroxidase and glutathione reductase and malondialdehyde (MDA) content. Cultivars showed different responses to salt stress. Cultivars Roshan, Kavir and Karchia showed lower yield losses. With increasing salinity treatment levels, MDA content and antioxidant activity increased except for catalase. Cultivars Roshan and Kavir were showed the highest antioxidant enzyme activity, but the lowest MDA content. Cultivars Qods and Shiraz were showed lowest antioxidant enzyme activity, but the highest MDA content in flag leaf blade. In salt tolerant cultivars, a higher antioxidant enzyme activity was accompanied with lower MDA content, resulting higher capacity to eliminate active oxygen species and yield stability. Correlations coefficient analysis exhibited increasing of antioxidant enzyme activity in salt stress condition with no considerable effect on grain yield, while chlorophyll and MDA content illustrated negative correlation with grain yield and so a main role in yield.

An experiment was conducted to determine the aging mechanism in safflower seed using natural aging treatment (storing seed at room temperature for six years) and accelerated aging (incubating the seed at 41?C and close to 100% relative humidity for 4, 8 and 12 days). The results indicated that both natural and accelerated aging reduced germination percentage, seed vigor and activity of Catalase (CAT), Peroxidase (POX) and Ascorbat Peroxidase (APX). The results also show that Malondialdhyde (MDA) content, electrolyte leakage and Mean Time to Germination (MTG) enhanced under natural and accelerated aging. The germination percentage in accelerated aging (from 94 percent in control) reached 64, 5 and 41 percent within 4, 8 and 12 days of treatment respectively. The increase in MTG was higher in natural aging than in accelerating aging. The decrease in ascorbat peroxidase activity in the aging treatments were higher than those in catalase and proxidase activities. Decrease in antioxidant enzyme activity resulted in enhanced Reactive Oxygen Species (ROS) and lipid peroxidation. Lipid peroxidation and membrane damage resulted to decrease seed germination and vigor. A high correlation was obtained between MDA content and germination as well as seed vigor in both accelerated and natural aging suggesting that lipid peroxidation plays an important role in safflower seed deterioration in natural and as well in accelerated aging.