Natural growth inhibitors associated with the cotyledon effect in light-grown dwarf and tall beans

The contents of non-acidic, acidic and bound growth inhibitorsin hypocotyls and cotyledons were compared between dark- andlight-grown dwarf and tall beans by means of thin-layer chromatographyand bioassay. In the non-acidic fraction, one major inhibitoryactivity appeared on the chromatogram, but its Rf zone was differentbetween hypocotyls and cotyledons. In both the acidic and boundinhibitor fractions, one major inhibitory activity appearedat the Rf zone corresponding to ABA. The ABAIike substance whichwas the major inhibitor in the hypocotyl was more abundant inlight-gorwn than dark-grown ones, especially in the dwarf variety,but light irradiation did not cause its transport from cotyledonsto the hypocotyl. A larger amount of bound ABA-like substance,which was the major inhibitor in the cotyledon, was presentin the dwarf than the tall variety regardless of the light condition.Cotyldon-enhanced photoinhibition of hypocotyl growth couldnot be explained by the levels of the xanthoxinand ABA-likeinhibitors, or the transport of these free inhibitors from cotyledons. (Received September 8, 1977; )