Padronização do teste de envelhecimento acelerado em sementes de acácia-negra (acacia mearnsii de wild.)

Abstract

In Brazil, acácia-negra (Acacia mearnsii wild) is grown to produce tannin and as a source of energy. The use of the standard germination test to determine physiological quality of the seeds lots has been criticized by researchers and producers of many different cultures. As a result, doing vigor in addition to germination test has become a more and more often recommendable practice. Among them, the accelerated aging process is a test that verifies how the seeds resist stress exposing them to high temperatures and high air humidity. This way their velocity of deterioration is increased and then the standard germination test can be done. But as there is no way to standardize temperature and exposition time to do this experiment with acacia-negra’s seeds. The aim of this paper has been find a way to create a standard accelerated aging test in which the exposition time and temperature can be controlled. To achieve that we made a casual delineating in a bi factorial experiment 3 X 5, where the factors were three levels of temperature (40ºC ( 104F), 42ºC (107.6F), 44ºC ( 111.2F)) and five exposition time ( 0, 24, 48, 72, 96 and 120 hours). The break of the seeds dormancy happened by their immersion in 90ºC water, where they had to stay for 24 hours at atmosphere temperature. The accelerated aging process was achieved using boxes “Gerbox” with metallic screen, filled with 40mL of destilled water. After the aging process periods, the seeds were tested by the standard germination test which used four repetitions of 50 seeds distributed on a humid “germitest” paper and kept in BOD Camera at 25º C ( 77F) and at 12/12 hour- photo period. The evaluation of the germination percentage was made ten days after the sowing considering the percentage of normal seedlings. Afterwards, all the data was carefully revised admitting a 5% error probability. The number 1 observed portion presented the largest germination percentage and was classified as the best quality. The best discrimination of the portions was obtained at 40º C (104F) temperature, with 48-hour-exposition period to the accelerated aging process.