The effect of sodium hypochlorite and gibberellic acid on seed dormancy and germination of wild oats ( Avena fatua )

The seed coverings, including the pericarp and testa of the caryopsis and the hull, arc the main barriers to the exchange of gases and the penetration of exogenous gibberellic acid (GA 3 ) for germination of wild oats (Avena fatua L.). Dormancy was induced in seeds by immersing them in water for 15 minor longer. Dormancy induction was greater in those seeds immersed for up to 1 h in 6% sodium hypochlorite (NaOCl) and then 1 h in water than in those seeds immersed only in water for 1 h. The addition of GA 3 , to seeds subjected to NaOCl treatment for 15 min or less did not break dormancy, indicating a slow rate of entry, or the exclusion, of GA 3 , by the seeds. In the presence of GA 3 , germination increased with increasing exposure to NaOCl. Maximum germination was obtained by immersing dry seeds in NaOCl for 2 h, in water for 1 h, and then incubating the seeds in GA 3 . Gibberellic acid was not required for complete germination of imbibed, dehulled seeds immersed in NaOCl for 1 h then in water for 1 h, but it was necessary to use 10 −4 M GA 3 for complete germination of intact seeds that were treated with NaOCl or 2 h then with water for 1 h. Imbibed, dormant seeds that were dehulled and pierced required 10 −7 M GA 3 , to give complete germination in this study. Piercing of the seed coverings enhances GA 3 , penetration and thus increases the availability of GA 3 , for germination. NaOCl treatment to the seeds mimics the effects of piercing. NaOCl may also have caused loss of germination inhibitors or rendered these inhibitors susceptible to oxidation. However, prolonged NaOCl treatment resulted in either poor germination or seed disintegration.