▁for ▁germ ination ▁of ▁the ▁sp ore ▁and ▁fung al ▁branch ing . ▁Studies ▁with ▁root ▁extract s ▁support ▁this ▁hypothesis , ▁and ▁so ▁far ▁str ig ol act ones ▁are ▁the ▁candidate ▁mole cules ▁that ▁better ▁explain ▁this ▁increased ▁in ▁mit och ond rial ▁activity . ▁ ▁A ux in - medi ated ▁secondary ▁growth ▁ ▁It ▁has ▁been ▁established ▁that ▁secondary ▁growth ▁in ▁plant ▁is ▁mainly ▁reg ulated ▁by ▁the ▁ph y to h orm one ▁aux in . ▁However , ▁the ▁mechanism ▁of ▁aux in ▁secret ion ▁is ▁at ▁the ▁same ▁time ▁reg ulated ▁by ▁str ig ol act ones , ▁thus ▁the ▁latter ▁can ▁control ▁secondary ▁growth ▁through ▁aux in . ▁When ▁applied ▁in ▁terminal ▁bud s ▁of ▁stem , ▁str ig ol act one ▁can ▁block ▁the ▁expression ▁of ▁transport ▁prote ins ▁required ▁to ▁move ▁aux in ▁across ▁the ▁bud s , ▁these ▁prote ins ▁are ▁denomin ated ▁P IN 1 . ▁Thus , ▁it ▁was ▁not ▁surprising ▁that ▁when ▁analyz ing ▁str ig ol act one ▁def ic ient ▁mut ants , ▁they ▁were ▁found ▁to ▁present ▁an ▁over - expression ▁of ▁P IN 1 ▁protein , ▁which ▁facil itate ▁the ▁transport ▁of ▁aux in ▁in ▁the ▁terminal ▁bud s ; ▁aux in ▁prevent ed ▁the ▁mit otic ▁activity ▁of ▁these ▁bud s , ▁stopping ▁the ▁plant ▁to ▁initi ate ▁secondary ▁growth ▁and ▁branch ing . ▁In ▁conclusion , ▁plants ▁depend ▁in ▁aux in ▁transport ▁for ▁secondary ▁growth ▁init iation ▁or ▁in hib ition , ▁but ▁these