02102naa a2200217 a 450000100080000000500110000800800410001910000200006024502300008026000090031052013640031965300110168365300180169465300190171265300180173170000190174970000170176870000190178570000160180477300640182011188922013-08-23       1999    bl uuuu     u00u1 u    #d1 aPERES, L. E. P.  aEffects of Auxin, Cytokinin and Ethylene Treatments on the Endogenous Ethylene and Auxin-to-cytokinins Ratio Related to direct Root Tip Conversion of Catasetum fimbriatum Lindl. (Orchidaceae) into Buds.h[electronic resource]  c1999  aThe present investigation attempts to correlate the effect of the exogenous auxins, cyrokinins and ethylene with rhe endogenous ethylene and auxin-ro-cytokinin ratio, and with the direct root-to-bud conversion in Catasetum fimbriatum. lncubation of root tips with IAA and NAA strongly inhibited both root elongation and bud formation. On the other hand, treatment with IBA resulted in a conspicuous stirnulation of longitudinal root growth, while bud formation was retarded. High levels of exogenous zearin, iP and BA enhanced bud formation, and inhibited root growth. Ethylene production was measured in IAA, IBA and zeatin-treated roots. AlI growth regulators elicited ethylene evolution, which decreased considerably along the period of incubation. Addition of AVG to the media reduced ethylene evolution. Endogenous auxin, cytokinins, and ABA conrents were determined by means of HPLC and ELISA rnethods in root tips of C. fimbriatum pre-incubated with ethylene (CEPA) and cyrokinin (iP). Both exogenous substances stimulated bud formation and conduced to an endogenous IAAlCks rario favourable to Cks. From rhese results it is proposed that the stimulatory effect of exogenous Cks and ethylene on root-to-bud conversion of C. fimbriatum seems to be mediated by rhe establishment of an endogenous auxin-to-cytokinins balance favourable to shoot formation.  aOrchid  aOrganogenesis  aPlant hormones  aRoot meristem1 aKERBAUY, G. B.1 aSALATINO, A.1 aZAFFARI, G. R.1 aMERCIER, H.  tJournal of Plant Physiology, USAgv. 155, p. 551-555, 1999.