Showing 4 results for Nitrogen Fixation
M. Sepehri, N. Saleh Rastin, H. Asadi Rahmani, H. Alikhani,
Volume 10, Issue 1 (4-2006)
Abstract
Heavy metals have deleterious the effects on nodulation and N2 fixation of Rhizobium- Legume symbiosis, due to their inhibitory effects on the growth and activity of both symbionts. This research has been undertaken to evaluate the effect of Cd tolerance of native rhizobial strains on diminution of the Cd detrimental effects on Sinorhizobium meliloti-alfalfa symbiosis. For this purpose, a greenhouse experiment was conducted based on Randomized Complete Block Design. The treatments in this experiment included: plants inoculation with 6 bacterial strains (sensitive, partially tolerant and tolerant to Cd), 5 levels of Cadmium (0, 2, 5, 10, 20 mg/kg soil) and non-inoculated control. In different levels of Cd, the effects of bacterial inoculation on root nodule number and total amount of nitrogen in plant shoot were compared. The results indicated that soil pollution by Cd even at 2 mg/kg had significant effect on symbiotic properties of rhizobial strains, and according to Cd tolerance of various strains, the mentioned effect was different. Decreasing effect of Cd concentration on root nodules and nitrogen concentration in plants that were inoculated with sensitive strains in comparison with plants inoculated with tolerant strains was 68.31% and 40.8%, respectively. In this research, R95m was introduced as the best strain because of its ability for nodulation and nitrogen fixation.
S. Rajaee, H. A. Alikhani, F. Raiesi,
Volume 11, Issue 41 (10-2007)
Abstract
Azotobacter chroococcum is an important PGPR (Plant Growth Promoting Rhizobacteria) producing compounds needed for plant growth. The aim of this research was to study the effects of different native strains of Azotobacter chroococcum on growth and yield of wheat under greenhouse counditions. Seeds of spring wheat (Triticum aestivum L. var. Pishtaz) were inoculated with some Azotobacter chroococcum strains capable of producing IAA, HCN, sidrophore and fixing molecular nitrogen. The inoculation of wheat with those strains had a positive, significant effect on biological yield, seed protein percentage, thousand seed weight, leaf area, N, P, Fe and Zn uptake, in particular, by wheat. The increased growth of wheat was most likely due to the production of IAA and enhanced nitrogen fixation by inoculated strains. Some strains of Azotobacter chroococcum native to Chaharmahal va Bakhtiari are established as PGPR. Results also support the efficiency of Azotobacter chroococcum as an important biofertilizer in wheat cropping systems. The selected strains had a significant effect on wheat growth and yield, including biological yield and seed quality under greenhouse counditions. This beneficial effect of Azotobacter chroococcum on wheat is attributed mainly to IAA production and, to some extent to non symbiotic nitrogen fixation in the rhizosphere. So, these strains can potentially be used to improve wheat nutrition of micronutrients such as Fe and Zn, in particular.
M Modares Sanavi, M Amini Dehagh, M Gholamhoseni, M Panj Tan Dost,
Volume 13, Issue 48 (7-2009)
Abstract
In order to study the effect of air and root-zone temperature on yield, yield components, nodulation and nitrogen fixation of three annual medics, an experiment was conducted in controlled environment (growth chamber) at the Faculty of Agriculture, Tarbiat Modares University in 2006. The experiment was performed as a spilt split plot with the layout of completely randomized design with three replications. Air temperature at three levels including 15/10, 20/15 and 25/20ºC day/night, four levels of root-zone temperatures including 5, 10, 15 and 20ºC and three annual medics (Medicago polymorpha, M. radiata and M. rigidula) were randomized to main plot, sub plot and sub sub plot units, respectively. The results showed that there were significant differences among annual medics for dry matter production, yield components and nitrogen fixation. M. rigidula produced more leaves, stems and root dry matter, leaf and stem to root ratio, leaf number and area and forage yield than other annual medics. Also, three annual medics at 25/20ºC day/night air temperature (the highest one) produced more nodulation dry matter (8.85 mg/pot) and nitrogen fixation (7.7 mg/g dry matter) than other temperatures. Plants at the former temperature produced 8 and 2 times more nodulation and nitrogen fixation than 15/10ºC day/night air temperature (the lowest one), respectively. Low root-zone temperature up to 5ºC had severely negative effect on yield and nitrogen fixation in the three studied annual medics. Interaction among annual medics, air and root-zone temperatures showed that M. rigidula was better than other annual medics for yield, nodulation and nitrogen fixation at 25ºC air temperature and 15ºC root-zone temperature . The result showed that M. rigidula had normal growth and development compared with other annual medics at low root-zone temperatures. Thus, M. rigidula may be a better annual medic for cultivation in cold and moderate regions. Therefore, in the zones where soil temperature is lower than 5ºC during the season, cultivation of annual medics is not successful, but in the zones where soil temperature is greater than 10ºC, annual medics have normal growth and produce average yield due to better nitrogen fixation.
L. Rahimi, N. Aliasgharzad, Sh. Oustan,
Volume 15, Issue 58 (3-2012)
Abstract
Azotobacter chroococcum can improve mineral nutrition of plants through N2 fixation and plant growth promoting capabilities. Fourteen strains of A. chroococcum were isolated from rhizosphere of wheat plants grown in different field conditions around Tabriz, northwest of Iran. In a pot culture experiment with sterile soil, wheat plants (Triticum aestivum cv. Falat) were inoculated with 14 bacterial strains. Positive control received nitrogen fertilizer without bacterial inoculation and the negative control was left un-inoculated and without N- fertilizer. Totally, 16 trearments with four replications were arranged in a completely randomized design. The plant growth indices and N and P concentrations of shoot and root were determined at the harvest time. Results showed that the inoculation with Azotobacter strains caused a significant increase in shoot and root dry weights. Bacterial inoculation significantly enhanced the concentration and content of N in shoot and root. Phosphorus content was only enhanced (p<0.05) in the root. Translocations of N and P from root to shoot were markedly increased in bacterial treatments compared to the positive and negative controls. Moreover, strains 1 and 48 which showed relatively higher phosphate solubilizing capability and phosphatase activity in in-vitro assay also brought about higher P content and concentration in shoot and its translocation from root to shoot.
