Synergistic interaction of gibberellic acid and triazinone derivatives in the promotion of rice shoot growth

Forty-five 1,3,5-triazine-2,6-dione derivatives were synthesized and their plant growth-promoting activities examined by the rice (Oryza sativa) seedling test in the presence or absence of gibberellic acid (GA). For high activity in promoting the growth of rice seedlings and acting as active GA-synergists, a para-substituted or a 2,4-disubstituted phenyl group, a hydrogen atom and an alkoxy group were required in the 1-, 3- and 4-positions of the 1,3,5-triazine-2,6-dione molecule. 4-Ethoxy-1-(p-tolyl)-s-triazine-2,6(1H, 3H)-dione [TA], one of the most potent triazinones, synergized the effect of GA on the shoot elongation of different varieties of rice including normal type, dwarf mutants and chlorophyll-mutants. TA synergistically increased the growth-promoting activity of GA by both a simultaneous treatment at the same sites and separate treatments at separate sites of rice seedlings.