FILM COATING IMPAIRS LEACHING OF GERMINATION INHIBITORS IN SUGAR-BEETSEED

Polymer film coating has been applied to commercial sugar beet (Beta v ulgaris L.) seeds in the USA as an effective delivery system for agroc hemicals. This research was conducted to study the impact of polymer f ilm coating on sugar beet seed germination. Twelve seed tots, represen ting nine monogerm cultivars, had standard germination of 89 to 95%. A fter film coating (20 g of polyvinyl polymer per kilogram seed), the g ermination percentage varied from 68 to 94%. Six seed lots, including three lots of cultivar HH55, exhibited significant germination reducti ons after coating. Besides significant cultivar differences, seed lots within the same cultivar (HH55) also showed different responses to co ating. After removal of the pericarp, the true seed of sensitive culti var HH55 did not show germination reductions after coating. This indic ates that the interaction between film coating and pericarp factors ac counted for the germination reduction in film-coated seeds. Sensitivit y to film coating was alleviated by presoaking or peroxide treatments. A high negative correlation was found between absorbance at 265 nm (A (265) nm) of seed steep solution and coated seed germination percentag e (r = - 0.96**). The A(265) nm of steeping solution could be reduced to near zero by filtering the solution through the phenolic absorbent polyvinylpyrrolidone. Polymer film coating induced germination reduct ions in sensitive cultivars were likely related to restricted oxygen s upply to the enclosed embryo and to the retention of water soluble ger mination Inhibitors, which would normally be leached into the germinat ion medium and/or oxidized and deactivated.