Enhancement of plant growth activity of irradiated chitosan by molecular weight fractionation

Luan, L. Q.*; Nagasawa, Naotsugu; Tamada, Masao; Nakanishi, Tomoko*

The chitosan products irradiated at 25 - 200 kGy in 10 % solution showed a positive effect on the growth of barley, while the unirradiated chitosan inhibited the growth of this plant. The 100 kGy irradiated chitosan product with average molecular weight (Mw) approx. 16 kDa was found as optimal to plant growth activity. Separation of the degraded samples was performed using ultrafiltaration membranes and was found that the fraction with Mw in range of 1-3 kDa. not only showed a remarkable effect on the growth of barley and soy bean, but also significantly increased the activity of phytoalexin enzymes, namely phenylalanine ammonia lyase (87 %) and chitinase (186 %). This fraction also increased 15.8 % seed yeild of soybean after three month cultivation.