Study on biological activity of chitosan after radiation processing

In recent years there is a trend in industry to limit the usage of chemical compounds. Natural polymers are new promising materials that possess important properties like biodegrability or lack of toxicity. Radiation processing of natural occurring polymers is an area of current research for development of new applications. The aim of this study was to determine the impact of ionizing radiation modification on bioactivity of a natural polysaccharide. Chitosan with different molecular weights was investigated as a biostimulator – a biologically active substance that stimulates some growth processes in plants. Chitosan in solid state was irradiated with electron beam from an electron beam accelerator Elektronika 10-10 with a dose range from 50 to 300 kGy. The effects of irradiation on the molecular weight of chitosan were investigated by viscosity and GPC measurements. Non-irradiated and irradiated chitosan at concentrations 0.001, 0.01, 0.1 and 1 g/dm3 were used for greenhouse tests of its activity for growth promotion of Salix viminalis L. var. gigantea plant. Uniform rooted cuttings (20 per combination) were selected for the test and cultivated in aerated hydroponics culture containing Hoagland’s nutrient solutions plus respective amounts of chitosan. After six weeks of plant exposure to chitosan, data of selected parameters of plant growth were collected. In most cases, except the highest concentration, both forms of chitosan had stimulatory effect on leaf area, length of roots and of newly developed shoots. Also fresh and dry weights of these organs were greater in chitosan treated plants. The highest concentration of chitosan was stimulatory only for a number of roots and newly developed shoots while for other parameters was inhibitory. In comparable concentrations the stimulatory effect was greater for chitosan irradiated in comparison with the non-irradiated one.