IRANIAN JOURNAL OF BIOLOGY
Year:2005 | Volume:18 | Issue:1|Papers Count:10

Micrococcus luteus is one of the bacteria that exists in water and industrial systems and shows high potential for biofilm formation. M. luteus cause some problems in these systems. In this study isolation and identification of M. luteus were performed of biofilm from cooling tower. Cell surface hydrophobicity, biofilm formation and growth rate were measured by MATH and slide test methods with staining and numbering respectively. The effect of antimicrobial agents in biofilm removal and killing was evaluated by microtiter plate test. Results showed a high degree of bacteria cell surface hydrophobicity and biofilm growth rate. So indicated that non- oxidizing biocides such as sulfathiazol are unable for biofilm removal. In fact this biocide is suitable together with other biocide for control of stable biofilms. But ability of oxidizing biocide such as H2O2 and NaOCl for remove the biofilm are very high than non- oxidizing biocides. As a result these biocides are suitable for control the stable biofilms on the surfaces. Also biocides with detergenic properties such as ADBAC act as oxidizing biocides in order to remove the biofilm.

Cellobiohydrolase is one of the cellulase enzymes which is involved in degradation of cellulose, the most abundant biopolymer in nature. Trichoderma species are known as a useful source of cellulytic enzymes. In this research cellulase enzymes activity in 30 isolates of Trichoderma sp. were studied by rapid screening on medium containing swollen cellulose and isolate Trichoderma reesei (PTCC5142) was selected on the basis of clearing zone diameter (16 mm). The enzyme activity was measured in the optimum conditions for production of cellobiohydrolase enzyme in Trichoderma. In order to obtain the optimum conditions: the selected isolate was grown in Mandels media with CMC, Avicel and Filter paper as carbon source at pH 4, 5,6, and7. Lactose and cellubiose were added to media as inducer agents. Media were incubated at different temperatures (25, 28 and 320C) for 14 days. Samples were collected in 24h intervals, and enzyme activity was measured. Results showed that the optimum conditions for hyperproduction of cellobiohydrolase were pH=5, CMC as carbon source, temperature 28 0C, lactose as inducer on 7th day. After screening the cellobiohydrolase activity of all 30 isolates in the optimized conditions, results showed that isolate Trichoderma reesei (PTCC5142) with the highest enzyme activity (4.45U/ml) was the best producer of cellobiohydrolase enzyme.

Calcium plays an important role in the resistance of plants to the salt stress. In the present research, the effects of different calcium salts (Calcium Sulphate, Chloride and Nitrate) at various concentrations on the resistance of Descurainia Sophia which were under salt stress were studied. The plants were grown in vermiculite medium using pots. Before applying the salt treatments, plants were subjected to a based nutrient solution (Hoagland solution) for 1 week. After 8 weeks, the shoot and root length, shoot and root fresh weight and the concentration of Na+, Ca2+, K+, Zn2+ and Fe2+ in plant tissues was determined by using atomic absorption method.To assess the effect of salinity and Calcium treatments on electrophoretic polypeptide patterns, shoot and root proteins were separated on SDS-PAGE gels. All data were analyzed by using full randomize plots and one-way ANOVA (LSD test). The results indicated that solutions containing 5 mM CaCl2 and 5 mM CaSO4 with 50mM NaCl have best effect on plant morphological (FW, DW and root and shoot length) and chemical paramteres (K+, Fe2+ and Zn2+). Comparison between Polypeptide patterns of treatments showed that the Calcium effected proteins synthesis in plant under salt stress. With the plants treated with 25 and 50 mM NaCl, polypeptide bands (56 KDa ) were more condensed than with the control. Bands of polypeptide with the molecular weight of 66-170KDa were observed in plants treated with 25, 50 and 75 mM NaCl. These bands were not observed in plants pretreated with Calcium ion.

Rice is one of the most important crops in agriculture and it has the highest production in whole world after wheat. Several investigators have worked on nitrogen nutrition in rice especially on ammonium and nitrate nutrition. The metabolic pathways and assimilation of ammonium and nitrate is not similar in plants and under some circumstances may lead to senescence. In this research, Effects of ammonium and nitrate nutrition on senescence of rice was investigated. Our data indicated that nitrate treatment induced the higher growth of shoots and roots. The shoot/ root ratio increased in ammonium fed plants that indicated higher inhibition of root growth in compare to shoot. The soluble and non- soluable carbohydrates content increased significantly in nitrate fed plants in compare to ammonium fed ones in both roots and shoots. The chlorophyll concentration was significantly higher in ammonium treatment in compare to nitrate ones. However, the chlorophyll a/b ratio did not changed significantly. The protein content increased significantly in ammonium fed plants in compare to nitrate fed ones in both roots and shoots. Also the proline concentration was significantly higher in ammonium fed plants than in nitrate ones. On the contrary, total phenolics concentration increased in nitrate treatment but not in ammonium ones. However, the increase in phenolics was no statistically significant in nitrate- fed plants as compared with the ammonium- fed plants.

Stipa barbata Desf. is important for fooder and prevention of running sands. According to ISTA reports, all seeds of this species have shown dormancy that causes reduction in seeds viability. In this study, seeds of Stipa barbata is collected from five pronances of Isfahan including: Semirom, Natanz, Feridan, Tangecheshmeh and Tiran. Then dormancy breaking treatments were done in completely randomized design in four replications. Germination percentage and mean daily germination and allometric coefficient were measured. Then best treatment was recommended. Results showed that the best dormancy breaking treatment for Stipa barbata seeds are A) alternative temperature (13/230C) in dark/light regime (16/8), B) use of 250 ppm GA3 for 48 hours, C) remove of lemma and palea. The highest and the lowest viability are in Natanz and Tiran pronances respectively. High correlation between germination percentage and mean daily germination was observed. This indicates that the germination percentage, also mean daily germination could be the best indicator for evaluation of viability of this species.

The Iranian desert plants have evolved adaptive mechanisms to tolerate harsh environmental conditions throughout the years. As a result, these plants have developed great genetic potential for tolerance toward abiotic stresses such as drought and salinity. One of such plants is genus Aeluropus which is an intertrible and native relative of wheat. In this research, plant culture of A. lagopoides and A. littoralis in controlled conditions with methods such as seed or vegetative propagation, hydroponic culture as well as suspension and callus cultures and subsequent regenerations were determined. We found that plant reproduction via stolon is the best way for vegetative propagation. In addition, it was shown using 2 mg/l auxin and 1-2 mg/l cytokinin hormones induced the highest embryonic callus formation from root tip explants. The small, fragile and milky calli were selected for establishing suspension culture. A combination of kinetin and auxin treatment induced embryonic culture form the suspension cells. These methodologies would be valuable in upcoming investigations aimed at elucidation of plant molecular responses to salt and drought stresses.

In order to evaluation of row spacing and seed value on quality characteristics in Koohdasht wheat (Triticum aestivum L.) an experiment was conducted under dry land farming in experimental farm of Agricultural Research center of Gonbad during 1380- 1381. The experiment was arranged as randomized complete blocks design with yhree replications. The treatments resulted from the factorial combination of three row spacing (12.5, 17 and 25 cm) and four seed value (250, 300, 350 and 400 seed per m2). Zeleny index was significantly affected by different seed value and water adsorption percentage was significantly affected by interaction effect. Study of results showed that the best row spacing is 17 cm and seed value is 300- 350 seed per m2.

In this research the effect of different bands of UV- radiation on the quantity of chlorophyll a, b, total chlorophyll, anthocyanine, carotenoids, flavonids and UV-absorbing pigments in leaves of the Glycine max were studied. Studied showed that in those plants which were treated with UV -A (2.73wm-2), the contents of these pigments were not significantly different in comparison to the control. While irradiation of the plant with UV-B (1/15wm-2) and UV-C (2.66wm-2) caused significant decrease in chlorophyll a, b, total chlorophyll and carotenoids. Decrease in carotenoid pigments was less significant when compared with chlorophyll. The reason for that probably is the sensitivity of the chlorophyll to the UV irradiation which should be highest in comparison with carotenoids. Other possibility is the increase in carotenoid synthesis which will act as protective pigments against UV radiation. Because the rate of this pigment on detoxification of different Active oxygene species and quenching of the triplet excited chlorophyll in photosynthetic is well known. The quantity of antocyanine, flavonoids and UV- absorbing pigments in treated plants were significantly increased these pigment have high absorption in UV spectrum of light and therefore could be used as UV absorption compounds by plants to prevent penetration of UV to the more sensitive tissues . The role of flavonoids in quenching of Hydrogene peroxide and other species of active oxygen could well describe. The defensive reaction of plants against uv radiation which will discussed in this paper.