Abstract: Seeds of Dalbergia fusca , an endangered tree species endemic to Yunnan province of China were used to study the inhibitory effects of abscisic acid (ABA) and the antagonism of IAA, GA3 , 6-BA and ethephon to ABA in the seed germination . The optimum temperature for the seed germination was about 30℃ . There was no different effects of alternating photoperiod ( 14 h light and 10 h dark) and darkness on the seed germination . After treated by 0 .01 - 0. 1 mol/L ABA, the seed germination percentage was not affected , but the time course of germination was decreased , while those levels were
dramatically inhibited by 1 mmol/L and 2 . 5 mmol/L ABA . The seed germination percentage was not affected by 0 . 0001 -1mmol/L indole-3- acetic acid ( IAA) , gibberellic acid (GA3 ) , 0 . 0001 - 0 . 1mmol/L 6-benzyladenine ( 6-BA) , and 0 . 001 - 10 mmol/L ethephon ( the ethylene donor) , but was inhibited by 1mmol/L 6-BA . The inhibition effect of 1 mmol/L ABA on seed germination was antagonized by 0 . 01 - 1mmol/L IAA, 0 . 01 - 1 mmol/L GA3 , 0. 001 - 0 . 1mmol/L 6-BA, and 0 . 1--10 mmol/L ethephon , which were phytohormone type- and concentration-dependent . The antagonistic actions of 0 . 01mmol/L 6-BA and 0 . 1 mmol/L ethephon to 1 mmol/L ABA inhibition could not be increased by addition of 0 . 001 mmol/L IAA or 0 . 001 mmol/L GA3 . The antagonistic action of 0 .1 mmol/L ethephon to 1mmol/L ABA inhibition , however , could be increased by addition of 0 . 01mmol/L 6-BA or 0. 1 mmol/L 6-BA, which resulting in higher germination percentage and enhancing seedling growth .

Key words: Abscisic acid