TIME SEQUENCE OF EFFECT OF ETHYLENE ON TRANSPORT, UPTAKE AND DECARBOXYLATION OF AUXIN

The effect of ethylene on the uptake, decarboxylation and basipetal transport of IAA-1-14C, IAA-2-14C and NAA-1-14C in cotton stem sections (Gossypium hirsutum L., var. Stoneville 213) was studied. A reduction in the capacity of cotton stem sections to transport auxin basipetally appears in sections excised from plants exposed to ethylene for only 3 hr and increases with fumigation time.In addition to reducing transport, increasing ethylene pretreatment periods from 3 to 15 hr also progressively reduced the uptake of 14C and increased the release of 14C as 14CO2 from IAA-1-14C. The effect of ethylene on the decarboxylation of IAA-1-14C was significant when expressed as either the cpm of 14C released per hr per mg dry weight or the cpm released per hr per mm2 in contact with the IAA donor. Comparative experiments using IAA-1-14C and IAA-2-14C demonstrated that the effect of ethylene on the decarboxylation of IAA was primarily a cut surface effect which apparently contributes to the reduction of IAA uptake by ethylene.Although ethylene significantly reduced the transport of NAA-1-14C, uptake was significantly increased rather than decreased as with IAA-1-14C while decarboxylation was unaffected.Ethylene pretreatment caused no significant changes in the dry weight or the cross-sectional area of the absorbing surface of the transport tissue. © 1969 Oxford University Press.