Preparation of Oligoalginate Plant Growth Promoter by γ Irradiation of Alginate Solution Containing Hydrogen Peroxide

Degraded alginate compounds with molecular weights of 7-26, 40-77, or 11-26 kDa were obtained by gamma irradiation, hydrogen peroxide (5% H2O2) treatment, or a combination treatment involving ionizing radiation and H2O2, respectively. The 14 kDa oligoalginate, prepared by the combined method, promoted the growth of mustard greens and lettuce at an optimal concentration of 75 mg/L. The growth promotion effects of the oligoalginate prepared by gamma irradiation in the presence of H2O2 were statistically equivalent to those of the oligoalginate prepared by gamma irradiation only. The combination of gamma irradiation and H2O2 reduced the required irradiation dosage by a factor of 9 relative to the oligoalginate produced by gamma irradiation only. The combination treatment (gamma irradiation/H2O2) may be carried out on a large scale at low cost to produce oligoalginate for use as a plant growth promoter in agricultural industries.