| Abstrakt: |
Seeds from heavily fruiting (“on-year”), mature untreated, and paclobutrazol-treated apple trees (Malus domestica Borkh. cv. Spartan) were sampled in mid-June 1987, mid-July 1987, and mid-July 1990. After seeds were freeze-dried, gibberellins (GAs) were extracted, purified, and fractionated via C18 reversed-phase high-performance liquid chromatography (HPLC). Nine GAs (GA1, GA3, GA4, GA7, GA8, GA9, GA19, GA20, and GA53) were quantified by the use of deuterated GA internal standards. Paclobutrazol trunk drench treatments reduced vegetative shoot elongation in the seasons that seeds were sampled by 55% or more. Between June 17, 1987 and July 15, 1987, the dry weight of seeds from both untreated and treated trees increased about 2.5 times and there were reductions, on a per seed basis, of GA4 in seeds from both untreated and treated trees, of GA7 in seeds from treated trees, and of GA9 in seeds from untreated trees. However, GA9 increased in seeds from treated trees. Changes in levels of some of the early-13-hydroxylation pathway GAs (GA15 GA3, GA8, GA19, GA20, and GA53) also occurred during the month. For mid-July harvested seeds, the pattern, with some exceptions, was that 2 years after paclobutrazol treatment (1987), levels of early-13-hydroxylation pathway GAs in seeds from treated trees were lower compared to controls but after 5 years (1990) their levels tended to increase. For the non-13-hydroxylated GAs (GA4, GA7, and GA9), 2 years after paclobutrazol treatment, GA4 levels were equal in seeds from untreated and treated trees, GA7 decreased in seeds from treated trees compared with controls, but GA9 levels increased. Levels of these three GAs were higher in seeds from treated trees 5 years after treatment (1990) but levels of GA4, GA7, and GA9 dramatically increased in seeds from treated trees 4 years after treatment (1989), as we previously reported. |
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