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 applications of gibberellin (GA). Wildtype Solanum tuberosum ssp, andigena required short days for tuberization, whereas their dwarf siblings tuberized under long days. Nevertheless, shortening the photoperiod also enhanced tuberization of dwarf plants and caused an increase in leaf angle and a reduction in internode length of both genotypes. The potential 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 metabolite levels was by radiocounting after HPLC. The data indicated a reduced conversion of GA(12) to GA(53) in dwarf plants, a difference which may be responsible for the dwarf morphology, although other explanations cannot be ruled out. Dwarf plants contained much less GA(1) as measured by GC-MS. We did not detect differences in [C-14]GA(12) metabolism between plants grown under 10-h versus 16-h photoperiods, in either wild-type or dwarf plants, even though other wild-type plants contained less GA(1) under short photoperiods than under long photoperiods.