Characterization of low molecular weight fragments from gamma irradiated κ-carrageenan used as plant growth promoter

Radiation degraded κ-carrageenan (1% solution at absorbed doses of 20kGy and 30kGy) were tested for its plant growth promoter (PGP) effect on pechay plants under hydroponics condition. Results revealed that higher PGP effects were found in κ-carrageenan irradiated at an absorbed dose of 30kGy. Mw of irradiated κ-carrageenan as measured by GPC were determined to be 7362Da and 6762Da for 20kGy and 30kGy, respectively. Fractionation of the irradiated κ-carrageenan (30kGy) was done to separate different Mw fractions using Mw cut-off filters of 1kDa, 3kDa, and 5kDa. The PGP effect of the different retentates showed that biological activity in plants followed the order of 5kDa>3kDa>1kDa using hydroponics condition but the reverse was observed in the order of 1kDa>3kDa>5kDa when absorbed in plants by foliar spraying. GPC chromatogram indicated at least three (3) low molecular weight (LMW) fragments from radiation modified κ-carrageenan solution with an Mw