MORPHOLOGY AND [C-14] GIBBERELLIN A(12) METABOLISM IN WILD-TYPE AND DWARF SOLANUM-TUBEROSUM SPP ANDIGENA GROWN UNDER LONG AND SHORT PHOTOPERIODS

Potato tuberization is promoted by short days and inhibited by applica tions of gibberellin (GA). Wildtype Solanum tuberosum ssp, andigena re quired short days for tuberization, whereas their dwarf siblings tuber ized under long days. Nevertheless, shortening the photoperiod also en hanced tuberization of dwarf plants and caused an increase in leaf ang le and a reduction in internode length of both genotypes. The potentia l role of GA metabolism in tuberization as influenced by dwarfing and photoperiod was investigated by studying the metabolism of [C-14]GA(12 ) in shoots of wild-type and dwarf potato plants. Measurement of metab olite levels was by radiocounting after HPLC. The data indicated a red uced conversion of GA(12) to GA(53) in dwarf plants, a difference whic h may be responsible for the dwarf morphology, although other explanat ions cannot be ruled out. Dwarf plants contained much less GA(1) as me asured by GC-MS. We did not detect differences in [C-14]GA(12) metabol ism between plants grown under 10-h versus 16-h photoperiods, in eithe r wild-type or dwarf plants, even though other wild-type plants contai ned less GA(1) under short photoperiods than under long photoperiods.