Seed dormancy mechanism in wild rice (Zizania aquatica).

In a study of seed dormancy in wild-rice, scraping to remove the pericarp over the embryo 24 h after harvest resulted in 55% germination, compared with no germination in intact seeds or in those punctured at the side of the embryo, whereas 33 and 79% of 1- and 2-yr-old viable seeds, resp., had to be punctured before they would germinate. Percentage germination of fresh scraped seed was reduced by adding pericarp scrapings or fresh hulls (paleas and lemmas) to the germinating medium. This effect was removed by washing and was not produced by hulls of 1-yr-old seed. When freshly harvested seed was stored for 1-2 wk in water at 1.5 deg C with or without removal of hulls, the presence of hulls reduced seedling survival, but no differences occurred after storage for 4 wk. GA at 0.01-5.0 mu M increased germination in dormant freshly-harvested seed and in partially dormant seed stored for 90 days, but had no effect on non-dormant seed stored for 130 days. Kinetin at 0.01-5.0 mu M alone had no effect on germination, but differences occurred in combination with GA and seedlings were less etiolated and had more normal root development when kinetin was combined with GA than with GA alone. It appeared that inhibition of germination in fresh seed was caused mainly by inhibitors in hulls and pericarps, with some effect from pericarp mechanical resistance effect from pericarp mechanical resistance and in older seed by pericarp impermeability.