Poster: Hormones
Abs #
640: Transport of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA) in corn roots
TFIBA is a unique and strong promoter of root growth but inhibits shoot elongation. Among several possible biochemical functions, its effect on ethylene is most notable. In addition to interfering with ethylene action, TFIBA could also competitively interfere with auxin transport. To test this hypothesis we conducted experiments with 2 d old corn roots (Zea mays, cv Pioneer 3085) from which the apical 5 mm were excised. Agar donor blocks (1.5 mm3)were prepared by dialysis against TFIBA (1 to 100 mM in 5 mM CaCl2) and applied to the tip or cut surface to study basipetal or acropetal transport, respectively. Untreated agar blocks served as receivers on the opposite end. After 1 to 4 hours of transport, the agar blocks and the root tissue were extracted in methanol, dried, methylated and quantified by GC/MS. The data were calibrated by measuring known quantities of TFIBA (1 to 80 ng). The uptake of TFIBA (4 - 40 ng per segment/h) led to higher quantities in the tissue than remained in the donors. However, the transition from tissue to receiver coincided with almost complete degradation of TFIBA. This observation and earlier measurements showing that TFIBA enhanced auxin transport when applied to the receiver, suggest that TFIBA interferes with auxin transport, possibly by protection from oxidation. Future studies will show if this protection results from competitive inhibition or transport specific steps. Supported by NASA grant NAG10-0190.
