Enhancement of plant growth stimulation activity of irradiated alginate by fractionation

Alginate with the weight-average molecular weight (Mw) approximately 900 kDa and ratio of M (mannuronate)/G (guluronate) about 1.3 was irradiated by gamma Co-60 in aqueous solution at doses up to 200 kGy. The irradiation dose was shown to be a function for reducing Mw and molecular weight distribution of irradiated alginates. The distribution of oligomer fractions in irradiated products was also investigated by separation using ultrafiltration membranes. The irradiated alginate with Mw approximately 14.2 kDa was found to have a positive influence for growing of barley and soybean. The irradiated oligoalginate fraction with Mw ranging from 1 to 3 kDa displayed the strongest effect on the growth and development of the mentioned plants at low concentration (20 ppm). It is suggested that oligoalginate with Mw in the range 1–3 kDa is a trigger for the growth and development of plants.