Mechanical scarification of dormant wild rice seed.

Dehulled dormant seed of Zizania aquatica was tumbled with crushed granite in a small rock polisher or scraped with a razor blade to remove the pericarp above the embryo. Seed tumbled in the laboratory for 1 h gave 44-60% germination in water depending on the seed lot. Scraped seed gave 65-100% germination 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 glasshouse before flooding gave an average germination of only 13% compared with 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 glasshouse stands.