Plant growth promoting cyanobacteria and their distribution in terrestrial habitats of Iran

In this research heterocystous cyanobacteria were isolated from paddy soils and used as algal extracts in a pot culture of vegetable crops. The first aim of this research was to study the distribution of algal species isolated from different rice (Oryza sativa L.) cultivation regions of Iran. Soil samples were collected from seven main rice cultivation provinces situated in perhumid and semi-arid regions of the country. In total, 49 heterocystous morphospecies were isolated from 20 locations. Among these taxa, Anabaena and Nostoc were found to be the dominant genera at most stations. The effect of algal extract on vegetable crops was the second aim of this experiment. After isolation and identification of these taxa, monoalgal cultures of two isolates were carried out by growing the isolates in nitrate-free BG-11 medium. Pot experiments were carried out by spraying algal extract on soil of treated plants. Growth of plants was evaluated by measuring growth parameters such as plant height, root length, dry and fresh weight of plant as well as leaf number after 40 days since planting. Statistical analysis showed that there are significant differences in studied parameters as compared to the control. In complementary studies nitrogenase activity of these taxa was determined by the acetylene reduction technique and identification of phytohormones was performed with the high performance liquid chromatography (HPLC) method. As result of this study, chemical content of algae extracts and production of plant growth-stimulating substances such as phytohormones can be proposed as factors affecting plant growth parameters.