Transport of abscisic acid

The transport of abscisic acid in cotyledonary petiole sectionsof cotton seedlings was investigated using (2-¹⁴C)-ABA in adonor-receiver system. Using the intercept technique, a transportvelocity of 22.4 mm/hr was determined. This velocity was foundto be independent of the length of the petiole or of the concentrationof ABA applied. In a 24-hr period 70% of the applied ABA movedthrough the tissue sections. No polarity was found in any ofthe studies. The capacity of the transport system decreased with increasingage of the tissue and with increasing time of pre-exposure toABA. When metabolism of the tissue was restricted by cold temperature,low-O₂ tension or DNP treatment, transport was inhibited 80to 98%.The distribution of ABA in the petiole during transportwas also investigated. The results are discussed in relationto the well-studied transport of IAA and in relation to thephysiologicalrole of ABA. ¹ Present address: Stanford Research Institute-Irvine, 19722Jamboree Blvd., Irvine, Calif. 92664, U.S.A. (Received November 30, 1970; )