modern research physics

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The effect of various CuCl2 concentrations at rosette stage on protein level, catalase and peroxidase activities of leaf and root of two canola cultivars were studied under greenhouse conditions. The experiment was conducted as factorial in completely randomized design with 4 replications and 4 treatments (0, 100, 300, and 500µM CuCl2). In general, protein concentration and catalaze and peroxidase activities were increased with increasing CuCl2 concentration. This enhance was more in PF cultivar than Hayola, and was more in root than leaf. Thus, it seems that PF cultivar has more ability in protein biosynthesis and antioxidant enzymes activation in compare with Hyola in stress conditions. Therefore, PF can be introduced as a cultivar with more tolerance to cupper stress, in compare with Hayola cultivar.

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Aluminum toxicity is one of the most important limiting factors for plant growth and development in acidic soil (pH <5.5). Soil acidity and consequently availability of Al in the soil can be accelerated by some farming practices and acid rain. The mechanisms of Aluminum toxicity have not been elucidated yet. The first response of the plant to aluminium toxicity is the inhibition of root elongation, that is apparently resulted from increasing of cell wall cross links. Therefore, the effect of aluminium on activity and gene expression of enzymes involved in phenolic compounds biosynthesis such as phenylalanine ammonialyase and peroxidase was investigated in this research.To this end, the flax seeds grown in Hoagland’s solution were treated with 0, 50 and 100 &muM aluminium (as AlCl3. 6H2O). The results showed that aluminium decreased root growth but increased wall bound phenolics content, compared with those of the control plants. Increase of the activity of peroxidase especially in ionically and covalently fractions in Al-treated roots was consisted with reducing root growth.  Increased activity, PAL expression and lignin contents were observed in higher concentrations of aluminum. The investigation of the expression of peroxidase isozymes, Flxper1 and Flxper3 suggested that Flxper3 is the isozyme which is more involved in aluminium toxicity in flax roots.  

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Citrus fruits are tropical and sub-tropical crops. The main problem in sub-tropical area is chilling and frost damage. Regarding the sensitivity of citrus fruit to low temperature and the conjunction of the fruit harvest season with low temperature, the investigation of the physiological impacts of low temperature treatments are very important. In this study, flavedo tissue of five cultivars of citrus fruit was examined to compare some enzymatic antioxidants activities including Superoxide dismutase (SOD), Ascorbate peroxidase (APX), peroxidase (POD) and Catalase (CAT) under various cold treatments, i.e. control (~15), 3, 0, -3 and -6 ^°C in two stages of before and after ripening of the fruits. The high activity of SOD enzyme in the flavedo tissue of the examined cultivars indicated that this tissue is the first defensive line of the fruits facing low temperatures treatments. The activity of CAT enzyme in the flavedo tissue of Sanguinello before and after ripening stages was higher in all low temperature treatments compared with other cultivars. Unshiu and Local Orange had maximum and minimum activity of APX enzyme, respectively in both stages. Also, Unshiu, Sanguinello and Local lemon showed increasing activity of POD enzyme by decreasing temperature

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Manganese (Mn) is a micronutrient that is essential for plant growth and develop-ment. Meanwhile, an excess amount of Mn is one of the most important growth limiting factors in acid soils. The present study was undertaken to identify the effects of excessive Mn on the physiological aspects of tea plant. To this end, 2-year old rooted cuttings of tea (Camellia sinensis L. assamica × sinensis) were grown in a modified Hoagland solution with pH=4.2 for 1 month with aeration in green house, with temperature of 27 ± 3 ˚C and photosynthetic photon flux of 101.5 µmol. m-2 s-1 (400-700 nm) at the plant level. After emergence of new, white roots with 5 to 10 cm in length, the plants were treated for 1 week with excessive Mn to a final concentration of 0.9 mM. After 1 week, the white roots were harvested and frozen in liquid N2 and kept at -80 ˚C until used for determination of PO activity, lignin and sugar as well as chlorophyll content. The activities of soluble peroxidase (SPO), covalently wall-bound peroxidase (CPO) and lignin content decreased by Mn treatment. On the other hand, the activities of ionically wall-bound peroxidase (IPO), sugar and chlorophyll contents increased by Mn treatment. These results suggest that excessive Mn may have beneficial effects on tea plant via lowering lignin content and increasing extensibility of the walls.