Abstract: A series of 1,2,4,6-tetrasubstituted pyridinium tetrafluoroborates were svnthesized and their plant growth regulating activities were examined. Some of them have been found to be effective in regulating the growth of rice and green gram。 Among them,1(4,6-dimethylpyrimidin-2-yl)-2,4,6-triphenylpyridinium tetrafluoroborate was the most effective in inhibiting the growth of rice, Preliminary studv shows that the heterocyclic radical at 1-position of parent pyridine enhances the growth inhibiting activity to rice, and alkyl containing oxygen atom at 1-position of parent pyridine enhances the growth inhibiting activity to green gram.

Key words: tetrasubstituted pyridinium tetranuoroborate, plant growth regulator, synthesis