Seed pre-treatment effects on Echinochloa crus-galli seed dormancy and germination

We investigated the response of dormant barnyard grass Echinochloa crusgalli (L.) P. B. seeds to various "germination pre-treatments" (GPT) which consisted in exposure of dormant seeds to conditions favourable for germination. Temperature during GPT (18, 25 or 36 degrees C) and length of GPT (1,2,4,8, and 16 d) were varied. The dormant seeds which did not germinate during GPT were chilled at moist conditions and 5 degrees C (stratification), for up to 400 days. The rate of dormancy termination in seeds exposed to stratification was checked in samples removed from chilled material at regular intervals and left to germinate at 25 degrees C and 4L:20D photoperiod. The course of dormancy termination in seeds exposed to GPT was compared with controls not exposed to GPT. Seed pre-treatment increased both the time required for dormancy termination by chilling and the percentage of seeds that did not germinate even after a long period of stratification. These seeds were not dead but conditionally dormant and germinated readily at 34 degrees C. The effect of GPT did not significantly increase with temperature of GPT period. Using temperature of 25 degrees C during GPT, the effect increased gradually with the length of GPT period and became fully manifested after greater than or equal to 4 d of GPT. Experiencing germination conditions by dormant seeds in the post-harvest period may influence pattern of germination in the field.