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was determined after electrophoresis in 10 % native polyacrylamide gel and specific in-gel staining as described earlier ( Barna et al., 1989 , 2014 ). Ion leakage test Leakage of electrolytes was measured as described previously ( Barna et al., 2011

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Heat shock treatment of near isogenic barley lines induced susceptibility against powdery mildew (Blumeria graminis f. sp. hordei, Bgh). When barley lines were immersed into hot water (48–49 °C) for 20 seconds one day before inoculation with Bgh race A6, the heat treatment increased susceptibility in susceptible barley cv. Ingrid and in its near-isogenic barley lines carrying different effective resistance genes. Microscopic investigations indicated vigorous development of the pathogen not only on heat treated susceptible Ingrid and resistant Mla, but also on Mlg-resistant and even mlo-resistant lines. However, when longer heat stress was used, infection density increased gradually on the susceptible Ingrid leaves, and the 40–50 sec heat treatment induced the development of visible powdery mildew colonies even on mlo leaves. Heat stress significantly increased leakage of ions from leaf segments from all barley lines with or without specific resistance genes and caused a late decrease of SOD and a slight increase in CAT enzyme activities, which correlated with the slightly down-regulated levels of hydrogen peroxide in the heat treated barley leaves. Significant increase of RNase activities was found after heat stress, and there was a slight degradation of total DNA as a consequence of heat pretreatment in all barley lines.

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(about 1 h), they were cut and placed on the surface of 10 cm 3 of distilled water in Petri dishes. Membrane permeability was determined by measuring ion leakage from cotyledons with an OK-102/10 conductivity meter (Radelkis, Budapest, Hungary) in

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. , Agarwal , V. , Gupta , S.C. 2009 . Comparison of drought-induced polypeptides and ion leakage in three tomato cultivars . Biol. Plant. 53 : 685 – 690 . Saneoka , H

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In the course of the Maize Consortium Project, investigations were made on the defence mechanisms employed by maize against various abiotic stress factors (low temperature, cadmium) and on the effects exerted by two compounds (S-methylmethionine, salicylic acid) capable of improving the stress resistance of plants to certain abiotic stresses. Salicylic acid (SA) was found to inhibit the uptake of cadmium (Cd), but caused damage to the roots, including a reduction in the activity of phytochelatin synthase (PCS), which meant that preliminary treatment with SA aggravated the damaging effect of Cd. It was also proved that as the result of 2-day treatment with Cd, there was a continuous rise in the Cd level in the plants, more Cd being accumulated in young leaves than in older ones. The PCS activity increased greatly after 24 hours, both in the leaves and in the roots, declining again after 2 days. The effect of SA was examined in both the hybrids and their parental lines, and the effect of this compound on the intensity of alternative respiration was also investigated. A comparison of chilling tolerance data and antioxidant enzyme activity indicated that these two parameters were not directly correlated to each other, i.e. antioxidant enzyme activity values could not be used to draw reliable conclusions on the chilling tolerance of maize lines and hybrids. With regard to the interaction between alternative respiration and salicylic acid, it was proved that exogenous hydrogen peroxide caused a similar increase in the ratio of alternative respiration to that observed after salicylic acid treatment. Abbreviations: SA, salicylic acid; Cd, cadmium; PCS, phytochelatin synthase; SMM, S-methylmethionine; PCs, phytochelatins; PAR, photosynthetically active radiation; TTC, triphenyl tetrazolium chloride; KCN, potassium cyanide; PSII, 2nd photochemical system; POD, guaiacol peroxidase; APX, ascorbate peroxidase; GR, glutathione reductase

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The present study was aimed to investigate the effect of different ultraviolet radiation doses on the growth, and antioxidant enzymes of three cultivars of soybean ( Glycine max L.) (‘Giza-22’, ‘Giza-35’ and ‘Giza-111’). The seeds were grown in plastic pots equally filled with a mixture of pre-sieved sandy loam soil, peat-moss and vermiculite (2: 1: 1) for two weeks. The planted pots were divided into four groups and exposed to white light (1,100 Lux) (control), 3.2, 6.4 and 12.8 KJ m −2 d −1 UV A+B radiation, respectively, for 30 days and then harvested. The results indicated that shoot dry weight was decreased with increasing UV A+B radiation doses; it was found that supplementation of UV A+B radiation increased root dry weight in all studied cultivars of soybean plants. With referring to oxidative stress, it was found that increasing UV radiation induced significant increases in H 2 O 2 concentration, lipid peroxidation and cell death (as ion leakage) in soybean cultivars. Increasing supplemental doses of ultraviolet radiations significantly induced reductions in all studied antioxidants (catalase, peroxidase and superoxide dismutase (SOD) activities and glutathione content).

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In the present study the physiological status of two wheat ( Triticum aestivum L.) cultivars subjected to polyethylene glycol-induced dehydration is evaluated. Wheat seedlings were exposed to either 8-d-long mild (15% PEG) or 24-h-long severe (30% PEG) osmotic stress by immersing their roots in PEG-supplemented Knop nutrient solution. Relative water content in the leaves and the levels of free proline, malondialdehyde, and hydrogen peroxide were chosen as indicative parameters corresponding to the degree of stress of the treated plants. Electrolyte leakage from leaf tissues of control and stressed plants was compared in terms of the common parameter Injury index used for characterizing cell membrane stability. In addition, a model test system was established for preliminary stress evaluation based on the kinetics of ion leakage. Short-term exposure to higher concentration of PEG was considered to be more harmful than prolonged mild stress as judged by RWC, proline and hydrogen peroxide accumulation, and injury index. The two cultivars demonstrated more obvious dissimilarities under conditions of prolonged mild stress than under severe stress.

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Apples were harvested at three different times (1 st, 2 nd and 3 rd) then stored at 1-3 °C, 85-90% R.H. for 5 months. Firmness, ethylene productivity, the distribution of calcium and potassium and the ion leakage were measured. The ultrastructure of the cell wall was studied by SEM and TEM and he activity of β-galactosidase and polygalacturonase and pectin content were determined. The ethylene evolution of fruits decreased by the harvest and storage time. At the beginning of storage, the ethylene productivity in the 1 st harvest apple increased up to a maximum value then declined. The 2 nd harvest fruits produced less ethylene than that observed in 1 st harvest fruits. No ethylene production was found in the 3 rd harvest fruits. Firmness was different according to harvest time, but that difference disappeared during storage. The permeability of membranes increased as a function of harvests and storage. The distribution of calcium was typical at the beginning, the highest concentration of calcium being near the core and skin, but by the end of the storage calcium moved from the skin towards the core. Potassium content was the highest near the core and decreased towards the skin, both in the fresh and stored apples. The activities of polygalacturonase and β -galactosidase were not influenced by the harvest time, but changed as a function of storage time. The autolysis of pectin and soluble carbohydrates increased during storage, mostly in the 3 rd harvest. At the beginning of storage, the cell wall and middle lamellae of the 1 st harvest fruits' flesh were not damaged. Large degradation of the middle lamellae was observed in the 2 nd and 3 rd harvest fruits. Lower membrane permeability, pectin degradation and PG enzyme activity were found in the 1 st harvest apples. The Idared apple should be harvested close to the climacteric maximum for better and longer storage.

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The effect of EEP on potassium ion leakage from S. aureus Fig. 4 The effect of EEP on protein leakage from S. aureus . Symbols as in Fig. 3. 2.6 Scanning Electron Microscopy (SEM) After exposure of S. aureus to EEP at different concentrations, cells

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