Thesis (M.Sc.)--Chulalongkorn University, 2007

Chitosan is a derivative of chitin (produced by deacetylation of the aceta amido group). Chitin is the principal component of the hard exoskeleton of shrimp, crabs and insects. Chitosan has become interesting not only because the abundant of crustaceans shells available from fishery industry, but also as a high potential natural material which can be used in various applications. Chitosan has ability to inhibit growth of certain bacteria and fungi which cause diseases in plants, induces plant defense mechanism, stimulates plant growth and enhances yield production. The objective of this study is to investigate the effects of chitosan concentrations on growth and yield production of rice Oryza sativa L. cv. Pathum Thani 1. Chitosan was prepared from crab shells and hydrolyzed by chitinase produced from Bacillus licheniformis SK-1. The percent of degree of deacetylation (%DD) and molecular weight of chitosan was determined. The chitosan prepared has 91 %DD and the molecular weight of 46 kDa. The effects of chitosan on seed germination, growth and yield production were investigated. Chitosan treatments consisted of four concentrations at 10, 20, 40, and 80 ppm, distilled water as a control. Chitosan did not affect seed germination. The difference among treatment was not significant. Chitosan increased plant height, leaf blade length and area, and rice straws dry weight. The most effective concentrations were 20 and 40 ppm. The study also found that chitosan treatment at 20, 40, and 80 ppm significantly increase panicles per plant when compared to the control (P<0.05). Other results showed that total grain number and grain weight were increased of 3 to 5 % by chitosan treatment, where 40 ppm was the most effective concentration. This study suggests that chitosan at the concentration of 40 ppm had a potency to stimulate growth and increase rice yield. The effective application of chitosan on rice plants is dependent on the concentration and the application methods of chitosan.