ance ▁produced ▁in ▁the ▁roots ▁was ▁stim ulating ▁this ▁process . ▁The ▁isol ation ▁of ▁str ig ol act ones ▁lead ▁to ▁a ▁series ▁of ▁tests ▁that ▁proved ▁that ▁this ▁comp ound ▁was ▁the ▁necessary ▁mole c ule ▁to ▁indu ce ▁germ ination ▁of ▁Str iga ▁species . ▁Later ▁on , ▁similar ▁comp ounds ▁were ▁proven ▁to ▁produce ▁the ▁same ▁effect : ▁s org ol act one ▁and ▁ale c rol , ▁both ▁of ▁them ▁presented ▁the ▁characteristic ▁la ct one ▁group , ▁so ▁they ▁were ▁class ified ▁as ▁str ig ol act ones . ▁To ▁indu ce ▁germ ination ▁of ▁par as it ic ▁plants , ▁str ig ol act ones ▁only ▁needed ▁to ▁be ▁present ▁in ▁trace ▁amounts , ▁in ▁the ▁order ▁of ▁ 5 ▁parts ▁per ▁million . ▁ ▁Sho ot ▁branch ing ▁h orm one ▁in hib ition ▁ ▁The ▁role ▁of ▁str ig ol act ones ▁as ▁branch ing ▁in hib itor ▁h orm one ▁was ▁discovered ▁because ▁of ▁the ▁use ▁of ▁a ▁new ▁set ▁of ▁mut ant ▁plants . ▁These ▁mut ants ▁presented ▁excess ive ▁growth ▁in ▁the ▁ax ill ary ▁bud s , ▁which ▁induced ▁their ▁terminal ▁stem ▁to ▁start ▁branch ing ▁ab norm ally . ▁Pre viously , ▁cy to kin ins ▁were ▁thought ▁to ▁be ▁the ▁only ▁mole c ule ▁involved ▁in ▁the ▁reg ulation ▁of ▁stem ▁branch ing , ▁but ▁these ▁mut ants ▁presented ▁normal ▁production ▁and ▁signal ing ▁of ▁cy to kin ins , ▁leading ▁to ▁the ▁conclusion ▁that ▁another ▁subst ance