Department of Plant Sciences

To study the effect of phosphorus solublizing bacteria as biological growth regulators of rapeseed Brassica napus L.) field experiments were conducted from September 2006 to October 2007 at the experimental farm of Arak Islamic Azad University in Iran. The study comprised four levels of phosphorus (P) solublizing bacteria and three rates of ammonium phosphate (0, 125 and 250 kg ha-1). The results showed no significant effects of the three ammonium phosphate rates on plant height, biomass yield and oil content in grains. However, number of pods per plant, grain yield and the P concentration in the shoot and, seeds were significantly increased with ammonium phosphate treatment. Compared to the untreated control phosphorus solubilizing bacteria (PSB) significantly increased average plant height from 77.7 to 97.3 cm, total dry matter from 7.5 to 11.4 t ha-1, number of pods per plant from 62.2 to 115.8, oil content in grains from 48.4% to 49.5, grain yield from 3.0 to 9.9 t ha-1 and P concentration from 0.21% to 0.33% in shoots, from 0.51% to 0.69% in reproductive plant parts (what do you mean here if not seeds?) and from 0.53% to 0.68% in mature grains. The combination of mineral P application at 125 kg P ha-1 and PSB application increased P concentration in the shoot dry matter from 0.21 % to 0.78 %.