Biofertilizers are used to improve the growth of seeds and plants. A range of beneficial effects of algal and cyanobacterial extracts on plants have been demonstrated, including improved germination and initial seed establishment, improvement of yield, and increased resistance to biotic and abiotic stresses. Rice is one of the oldest crops in the world after wheat and is the main food of millions of people in the world. Considering the beneficial effects of Nostoc cyanobacteria as biofertilizer, in this study, the effect of aqueous extract of N. commune on rice growth indices was investigated. Aqueous extract was prepared at a concentration of 5 g l-1 and then added to sterile Petri dishes containing 10 disinfected rice seeds in 0, 25, 50, 75 and 100% dilutions. Seedlings were harvested after 8 days and growth indices including germination percentage, root and shoot length, seedling weight, number of roots and shoot were examined. The results showed that shoot length, number of roots and seedling weight in treatments with concentrations of 50, 75 and 100% of the extract had a significant increase compared to the control, while root length at concentrations of 75 and 100% showed a significant decrease. The germination percentage and number of shoots treated with different concentrations of the extract did not show significant differences. According to the present results, the use of aqueous extract of N. commune can be effective in improving rice seed growth parameters.
