biological activities of these compounds were compared by three bioassays with those of indole-3-acetic acid and 4-chloroindole-3-acetic acid (4-Cl-IAA), which, like 4-CF(3)-IAA and 4-CH(3)-IAA, has a substituent at the 4-position of the indole nucleus. 4-CF(3)-IAA showed strong root formation-promoting activity with black gram cuttings which was 1.5 times higher than that of 4-(3-indole)butyric acid at 1x10(-4)