The physiological basis of seed dormancy in Arena fatua V. Action of ethanol and other organic compounds

Ethanol (50-200 mM )induced germination in four genetically pure dormant lines of Avena fatua L. The sensitivity to this treatment was moderate immediately after harvest and increased steadily during six months of after-ripening. This sensitivity to ethanol was detectable much earlier during after-ripening than with two other germination promoters, NaN³, and NaNO³, Because ethanol can overcome dormancy in freshly harvested caryopses, the mode of action of ethanol in these caryopses apparently differs from that of the two other promoters, azide and nitrate. Nevertheless, it is clear that induction of germination by the three promoters is fully gibberellin-dependent since in each case this response can be blocked by the administration of 2-chlorocthyl trimethylammonium chloride, an inhibitor of gibberellin biosynthesis. Short-term incubation treatments with ethanol were relatively more effective than continuous treatments. These brief treatments were most effective when presented near the beginning of seed imbibition. Among other organic compounds tested only acetaldehyde significantly promoted germination in all lines tested. Propan-1-ol, butan-l-ol, chloral hydrate, procaine, methanol and chloroform were marginally effective on the least dormant lines, while ether, formaldehyde, acetone and ethyl acetate were ineffective. The mode of action of ethanol in overcoming dormancy in both freshly harvested and partly after-ripened caryopses is discussed and the possible role as a metabolic substrate or anaesthetic is indicated.