Basipetal and acropetal transport of [3,4-(3)H]Gibberellin A 1 in short and long segments of Phaseolus coccineus second internode

Abstract

Transport of [(3)H]GA1 occurred freely through stem segments ranging in length from 6 mm to 8 cm. Only small amounts of radioactivity appeared in agar receiver blocks, particularly when transport in young, elongating, segments was measured. Little or no metabolism of [(3)H]GA1 appeared to take place during a 16 h transport period. With 6 mm segments, there was no indication of polarity in longitudinal transport. In 8 cm long segments, an apparent acropetal polarity of [(3)H]GA1 transport occurred in young, but not in mature, segments. However, it appeared likely that gibberellin transport, even in long young segments, was not truly polar, but could be influenced by the spatial distribution of growth centres in relation to gibberellin source.