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THE EFFECT OF TFIBA ON AUXIN TRANSPORT IN PRIMARY ROOTS OF ZEA MAYS L.  G. Ku and K.H. Hasenstein, Biology Dept. UL Lafayette, Lafayette, Louisiana 70504-2451

   Previous research has shown that the promotion of root growth of 4,4,4-trifluoro-3-(indole-3-) butyric acid (TFIBA) is partially due to its effect as ethylene antagonist but it is also possible that TFIBA affects auxin transport. Therefore, we studied auxin transport in apical segments of 2-3 d old primary roots of corn in the presence of this compound. The root segments were sandwiched between an agar donor and receiver, and tritiated IAA (10^-7 M) was applied to the cut surface. Auxin transport was measured in the presence of   100 µM TFIBA in the receiver, or donor, or both agar blocks for one and two hours. Based on the radioactivity of the receivers and uptake we found that compared to non‑treated controls, TFIBA enhanced transport when applied to the receiver by 50%. In contrast, uptake was promoted regardless of the site of TFIBA application from 17 to > 25 %.   After 2 h of transport the effect decreased. These patterns are consistent with TFIBA‑enhanced acropetal auxin transport. Future work will study the rate and direction of TFIBA transport and its possible effect on IAA metabolism.

(Supported by NASA grant NAG10-0190.)