Phormidium improves seed germination and growth parameters of berseem clover in hexadecane-contaminated soil

Petroleum is known as the main source of fuel and one of the most important environmental pollutants. Petroleum contaminated soil negatively influences plant growth and human health. Bioremediation of petroleum-contaminated soil could be achieved by adding cyanobacteria and photosynthetic microalgae in the soil. In the current study, the beneficial effects of cyanobacterium Phormidium sp. ISC108 treatment on seed germination and plant growth parameters were investigated on berseem clover plants exposed to 1% hexadecane- contaminated soil. For this purpose, after cultivation of berseem clover seeds in soil with 0 and 1% hexadecane, they were irrigated every two days by 3 ml Phormidium (OD600 = 0.7) and water for the cyanobacteria treatment and control, respectively. After 30 days, the biodegradability of hexadecane in the soil around the root was measured by gas chromatography mass-spectrometry (GC-MS). The results showed that Phormidium treatment accelerated germination of berseem clover seeds in both control and hexadecane- contaminated soil. Improvement of plant growth indices such as leaf area, plant fresh weight and leaf RWC due to cyanobacteria treatment was observed in hexadecane-contaminated soil. Hexadecane levels in the soil around the root of the plants irrigated by cyanobacteria were significantly decreased. In addition, the hexadecane degradation in the soil around the roots of berseem clover plant was increased in both control (water) treatment. In conclusion, due to positive effects of Phormidium treatment on seed germination, plant growth of berseem clover and hexadecane degradation, it can be effectively used to enhance plant capacity to cope with hexadecane toxicity in petroleum-contaminated soils.