An experiment was carried out to compare the period of exposure of pre-dried seeds from
the EMBRAPA 7 Taim cultivar of flooded rice to different oxygen concentrations to break dormancy.
Seeds were sowed in wet paper towel and put into a hermetical closed recipient where were set the 10, 20,
40, 60 and 80% oxygen concetrations for 48, 96 and 336 hours. After two first periods of exposure, the
seeds were placed in a germinator set, at the temperature of 25ºC to complete the period of the germination
test. In the treatment with 336 hours, the seeds were mantained all the time in the germinator. In the predrying
method, the seeds were kept at 42ºC for five days, afterwards they were taken to the germinator.
Seven and 14 days after the experiment has been installed the size and the percentage of normal seedlings
were measured. The 48 and 96 hours of expousure to different O2 concentrations did not effect the size of
seedling, but after 336 hours, concentrations higher than 40% supressed formation of normal seedlings. The
amount of normal seedlings increase after 96 hours of exposure to the 40% or more oxygen concentrations.
However, no more than 47% of seedlings showed to be normal under those treatments above described. The
pre-drying method is more efficient to break dormancy of seeds of flood rice from the EMBRAPA 7 Taim
cultivar than its exposure to high oxygen concentrations.