Polyamines, Hydroxycinnamoylputrescines, andRoot Formation inLeafExplants ofTobacco Cultivated inVitro Effects oftheSuicide Inhibitors ofPutrescine Synthesis

Invitro formation ofrootsisobtained directly, without intermediate growth ofcallus, fromfoliar explants ofatobacco (Nicotiana tabacum) plant cultured onMurashige andSkoog medium containing IAA.Auxin-induced rootformation wasaccompanied bysignificant changes inhydroxycinnamoylputrescine Increasing levels werefoundinleafexplants during thefirst 14 daysinculture; this wasfollowed bya sharp decline after 20 days. Early changes inputrescine conjugates weredetected in leaf explants before thevisible appearance ofroots. Anearly and transitory accumulation ofhydroxycinnamoylputrescines wasobserved intheroots. Freepolyamines (putrescine, spermidine, and spermine) inleaf explants androots werealways atalowlevel andonlysmall changes intheir concentrations wereobserved, a-DL-difluoromethylarginine and a-DL-difluoromethylomithine, specific, irreversible inhibitors ofarginine decarboxylase and ornithine decarboxylase, respectively, inhibited putrescine accumulation androotinitiation andreduced thefresh anddryweights ofleaf explants. Theseeffects werereversed byfreeputrescine orhydroxycinnamoylputrescines. Theresults reported heresuggestthathydroxycinnamoylputrescines areassociated withroot formation. Therelationship amongfreepolyamines, hydroxycinnamoylputrescines,