IRANIAN JOURNAL OF BIOLOGY
Year:2003 | Volume:13 | Issue:3-4|Papers Count:9

Regarding to science and technology development, presently the application of disposable food containers which has generally been made of high and low - density polyethylene are increasing. For studying the effects of the above disposable food containers which may have on the society health, the mutagenicity and carcinogenicity effects of these disposable food containers have been assessed by the Ames test. Mutagenicity assay has been done with Ames method applying Salmonella typhimurium strain TA 104. By the effect of mutation this strain has been missed the histidine synthesis potential. If this strain is cultured in minimal agar medium, no growth will be seen, because histidine has not been produced. In this research, polyethylene compositions has been added separately to minimal agar medium Salmonella typhimurium strain TA104 and compared to positive control index consisting of mutagen sodium azide and negative control index (distilled water). Carcinogen materials will cause a reverse mutation towards the synthesis of histidine and several bacteria will produce histidine. Their presence considering to colony numbers and comparison with negative control index containing several colonies produced by spontaneous mutation approved materials mutagenicity and compared. The obtained results showed that HOPE, disposable glass and food containers, bottle for carrying the liquids, milk plastic bags do not possess the mutagenicity property. LDPE which is generally transparent and made of monomers and free- radicals will cause reverse mutation in thin plastic bags for histidine synthesis. The plastic bags coated by liquid or solid oil will much more affected by mutagenicity. Mouse liver tissues microsomes obtained under sterile conditions have been added separately to minimal agar medium suspected to carcinogenicity and measured the effect of the carcinogen materials and bacteria status affected by reverse mutation and produced histidine.

Mutation has been used as an efficient method for improving the suitable characteristics in industrial microorganisms. In this research we compared the effect of UV radiation, the most important physical agent and treatment with ethidium bromide on mutagenesis of Saccharopolyspora erythraea NUR001, the producer of erythromycin. The spores of S. erythraea NUR001 was exposed to the various doses of the UV radiation and various concentrations of ethidium bromide, and then screening method was used for the isolation of the mutants resistant to erythromycin. The results obtained revealed that optimum conditions for mutagenesis with UV were 5cm distance from a 254nm UV source and 45 minutes radiation. The best concentration of ethidium bromide for mutagenesis was 10µg/ml. The results showed that UV radiation was more efficient than ethidium bromide in the production of mutants that showing increased resistance to erythromycin. The mutant exhibited higher resistance (9µg/ml) to erythromycin when compared with that of the parent strain (8Ilg/ml). In this research, the beneficial mutagenesis effect of UV on Saccharopolyspora erythraea NUR001 was more than ethidium bromide. We obtained the Saccharopolyspora erythraea NUR002.Compared to its parents, this strain was more resistance to high concentration of erythromycin.

Azospirillum brasillense is one of the nitrogen fixing microorganisms which in association with root of cereals and grasses, enhances growth and development of plants. In this research wheat seeds (T.aestivum) of three cultivars (Ghods, Roshan and Omid) were inoculated with two Azospirillum strains (Sp7 and Do1) and grown according to airoponic method. Inoculation increased density and length of root hairs and also in several cases were caused root hair deformation. These changes were directly dependent on the strain-cultivar combination. Strain Do1 induced the greatest density and branching of root hairs in cv. Ghods, whereas strain Sp7 stimulated the highest density and deformation of root hairs in cv. Roshan. The response of cv. Omid was less that the other cultivars. The effects of Azospirillum inoculation were mimictable by authentic indole acetic acid. The presence of IAA in culture filtrate of Azospirillum strains (Sp7, Do1) was confirmed by thin layer chromatography. Therefore, this study has veen demonstrated the important role of IAA in interaction between Azospirillum and wheat root and also density and defromation of root hairs.

Today many researchers investigate the effects of increased UV radiation caused by decrease in ozone layer. Production of reactive oxygen species (ROS) and oxidative stress in plant tissuee specially in photosynthetic tissue are one of the effects of this radiation. In this research, we used fluorescence tube enemates wavelength of 250-280, 280-320 and 320-390 nanometer, which include, UV-C, UV-B and UV-A respectively. To investigate some antioxidant activities including ascorbic acid (ASA), carotenoids, lipid peroxidation reaction and amouts of secondary metabolits which absorb UV radiation, we used seven days canola seedlings which have been exposed 30 min a days to UV radiation for 4 days. Measurment of ASA showed increased of these compound in this plant because of their role in removal of free radicals. chlorophyll decreased specially in B and C bands however carotenoids did not decrease significantly. Malondealdehyde (MDA) is the indicator of the lipid proxidation reaction. Significant increase in MDA in treated plant by UV in our experiment is the indication of fatty acid oxidation in the present of free radicals generated by UV radiation. Aggregation of UV absorbent compounds in epidermis layer is one of the protection mechanisms which plants used against increased UV radiation. The enzymes of the phenylpropanoid pathway were activated because of the UV radiation effects. This activation produced compounds like flavonoids and anthocyanins which prevent penetration of UV to the more sensitive tissue especially mesophylls tissue. In this experiment we observed significant increase of this compounds in UV treated seedlings of canola.

With the culture of various explant under certain cultural conditions, embryogenesis will result. In this research mbryos were obtained from several species of Hyoscyamus: H.arachnoideus H.pusillus, H.niger, from 2 distinct geographical regions, on MS mediums with various hormonal treatments. The results from statistical assessments showed that the highest embryogenesis were obtained with the following conditions: Culture of region 2 biennial H.niger stern segments on mediums of No .I (IAA=0.2mg/L), No. 3 (BAP=1.5mg/L), No. 4 (Kin=1.5mg/L), No. 7 (BAP=1.5, IAA=0.2mg/L), and No. 10 (Kin= 1.5, IAA=0.2mg/L). Culture of region 2 biennial H. niger roots on mediums of No. 4, 7, 10, and (BAP=1.12, IAA=0.09mg/L). Culture of region 2 biennial H. niger leaves on medium contianing Kin (1.5 mg/L). In addition, the highest embryogenesis frequencies were observed with: Culture of H.pusillus sterns on mediums No. 7; and 12. Culture of H.pusillus leaves on medium No. 3. Culture of H.arachnoideus leaves and sterns on mediums No. 7, and 12. Culture of region I biennial H.niger sterns on mediums No. 7, and 12. Culture of region 2 biennial H.niger roots, sterns, and leaves on medium No. 4, 7, and 12. Culture of region 2 biennial Hniger roots, and sterns on mediums No. 1, 3, and 10. The formation of plantlet resulted from the subculture of the obtained embryos on MS medium and MS medium contianing IAA (0.2mg/L).

Rangelands have long been of consideration and exploitation for human beings in economic, medicine, industries and high genetic stores. Physical disturbances such as grazing by domestic animals could affect diversity components. This research was carried out in the two differently grazed sites (grazed and ungrazed) in Torogh basin, south of Mashhad to determine and compare piant diversity of the two sites. Considering cumulative diversity curve of Brillouin and the minimal area, about 228 and 233 1m2 quadrats were established in grazed and ungrazed sites, respectively. Floristic composition along with canopy cover and abundance of each species were recorded in the quadrats. The data were subject to Diver and Nucosa program packages to calulate numerical indices such as species richness, diversity and evenness. The total number of 163 plant species, 93 in ungrazed and 70 in grazed site, belonging to 38 families were recorded in the area. The most important farriilies were Asteraceae, Fabaceae, Lamiaceae, Poaceae, Brassicaceae, Apiaceae, Caryophyllaceae, Boraginaceae and Rosaceae with 29, 22, 14, 14, 13, 10, 7, 5 and 5 plant species, respectively. Data analyses revealed the more diversity in ungrazed site that in grazed site based on the different indices of richness, diversity and evenness. In the grazed site, some species with high forage values became less abundant and even disappeared. There was significant difference based on t-test between values of the two sites measured by the Shannon index.

Germination of two wheat cultivars in different levels of temperature (0-45°C) were compared. Percentage of germination in Alamut at high and low temperatures was significantly higher than that of Zarrin. Based on the results, Alamut is resistant and Zarrin is sensitive cultivar to cold and heat. By using randomized complete block design with 12 treatments (2 cultivars×3 levels of temperature×2 duration of treatments) seedling of 4 days for 24h or 5h at 43°C (heat) , -4°C (cold) and 180oqcontrol) treated. After these treatments total protein and soluble sugars in leaves of wheat cultivars were determined. Cold stress (4°C/24h) causes increase of soluble sugars in leaves of two cultivars, while total protein content is not significantly changed. Heat stress (43°C) causes significantly increase of both soluble sugars and total protein in leaves of two cultivars. Electrophoresis of leaves proteins show expression of heat shock proteins (21, 17.5, 14.6 and 10 KD) in 43°C/5h treatment but not in other treatments.