Mechanical Scarification of Dormant Wild Rice Seed1

Abstract

AbstractWild rice (Zizania aquatica L.), which formerly grew only under natural conditions until the early 1960's, is now being grown as a cultivated field crop. A 3 to 6‐month, post‐harvest seed dormancy hinders the continued development of wild rice as a field crop. Part of this dormancy is due to an impermeable pericarp. Scarification with chemicals to increase permeability has not been successful, and scraping the individual seeds to remove the pericarp above the embryo is too time‐consuming. A small rock polisher was evaluated as a scarification device in this study. Three dehulled seed lots, one from greenhouse‐grown plants and two from field‐grown plants with different harvest dates were used. Samples from each were tumbled with dry crushed granite in the polisher for varying times or scraped with a razor blade to remove the pericarp above the embryo. Laboratory and greenhouse gemination were used to measure the resulting release of dormancy. Seed tumbled in the laboratory for 1 hour gave gemination percentages in water of 44 to 60, depending on the seed lot. Scraped seed gave gemination percentages of 65 to 100 for the corresponding seed lots. Tumbling resulted in less seed injury and required less time than scraping seed. Placing tumbled or scraped seed 1.5 cm deep into soil in the greenhouse before flooding gave an average gemination percentage of only 13 compared to 64 when seed was germinated in water. Transplanting seedlings from scarified seeds germinated in water was more successful than direct planting of scarified seed to establish greenhouse stands. Use of the rock polisher significantly accelerated scarifying wild rice seed with a minimum amount of injury. This method may be adapted to other high moisture seed that requires scarification.