The uptake movement and metabolism of ABA-2-14C has been studied in coleoptile and root segments of Zea mays, petiole segments and whole plants of Phaseolus vulgaris and intact plants of Alnus glutinosa. Acer pseudoplatanus and Betula pubescens. Using coleoptile segments ten millimetres in length, excised one millimetre from the apex, the following transport characteristics have been established; basal uptake of 14C exceeds apical uptake; there is a slight net basipetal polarital of accumulation of 14C in tissue halves further from the donors; velocity of 14C movement in either direction is less than 1.5 mmh-1; movement of 14C is independent of segment orientation, but dependent upon donor concentration; there is little or no export of 14C into agar receivers; there is a metabolically-dependent step in the transport process; only a small proportion of the 14C recovered from transporting. Using segments of differing shapes, the more closely the segment resembles a uniform cylinder of tissue the more any differences between apical and basal uptake and acropetal and basipetal movement are abolished. Using sub-apical root segments, there is a net acropetal polarity of 14C accumulation in the tissue, rates of movement exceed those in coleoptiles, and lowering the temperature has less effect on root transport of 14C than coleoptile transport. Movement of 14C in Phaseolus vulgaris petioles is non-polar at a rate of 5-7mmh-1. The movement of 14C in whole bean plants is dependent upon the method and locus of application of ABA-2-14C. In general, 14C distribution reflects movement from a source, through living tissues, to the more actively-growing regions of the plant. There are, however, differences between the 14C distribution following ABA-2-14C application and that following IAA-14C or sucrose-14C application and that following IAA-14C or sucrose-14C application. There is evidence of extensive metabolism of ABA-2-14C in bean tissue. Root-applied ABA affects the plant-water relationships of P. vulgaris. The movement and metabolism of ABA.2. Cin A. glutinosa and B. pubescene are basically similar to those in bean plants. Continuous root-application of ABA to plants of A. glutinosa slightly reduces growth but does not induce the formation of a dormant state. Continuous leaf-application of ABA solution to plants of A. glutinosa and B. pubescens, maintained under long days, does not appear to inhibit growth or induce the formation of resting buds. The lack of response may be due to poor uptake, low mobility and/or extensive metabolism of the applied substance
