Translocation and metabolism of [(3)H]gibberellins by light-grown Phaseolus coccineus seedlings

Tritiated gibberellins (GAs) A1, A4, A5 and A20 injected into the apical bud of light-grown Phaseolus coccineus L. seedlings were retained in the apical region and underwent little metabolism in 24 h. However, when injected into the hypocotyl, the [(3)H]GAs were extensively metabolised and redistributed. All four GAs were equally effective in promoting subapical elongation in shoot explants irrespective of apical or basal application. The metabolism and export of [(3)H]GA4 by excised organs incubated for 24 h in buffer solution was both quantitatively and qualitatively different to that of the corresponding treated organs of intact plants, suggesting abnormal metabolic conditions in explants. [(3)H]GAs applied to embryonic axes of germinating seeds were translocated into the cotyledons but no translocation in the reverse direction took place.