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

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Abstract
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 [3H]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 [3H]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. [3H]GAs applied to embryonic axes of germinating seeds were translocated into the cotyledons but no translocation in the reverse direction took place.