The germination percentage of peach [Prunus persica (L.) Batsch cv. Halford] seeds at 20°C was low (< 20%) after incubation at 5°C for as long as 35 days, but then increased considerably (> 40%) when the seeds were maintained at 5°C for longer than 42 days. Four zones of gibberellin‐like activity were found in partially purified seed extracts. Gibberellin‐like activity remained low in seeds incubated at 5°C for as long as 28 days, but increased significantly in three of these zones after 35 days, and in the fourth zone after 49 days. The increase in gibberellin‐like activity was evident prior to the transfer of the seeds to 20°C. Moreover, seeds maintained at 5°C germinated at this temperature after 63 days. For seeds incubated and germinated at 20°C, both the germination percentage and the gibberellin‐like activity remained low throughout the experimental period. Application of the growth retardant paclobutrazol to seeds after 28 days of a 49 day total incubation period at 5°C did not substantially reduce seed germination, although the increase in gibberellin‐like activity was prevented. Seeds did, however, require a longer time to germinate after transfer to 20°C and were dwarfed in appearance. Application of GA3 to seeds prior to stratification increased the percentage germination of seeds only when they had been incubated at 5°C for at least 35 days. The major changes in gibberellin‐like activity are, therefore, associated not so much with the processes which allow germination to take place in peach, but more with those processes which allow normal growth and development of the seedling.
Ethephon at 200 ppm applied to ‘Cresthaven’ peach trees [Prunus persica (L.) Batsch] in October delayed flowering by 7 days in the first year of this study, but only by 3 days in the 2nd year. Flower bud survival was reduced in both years by this treatment, although the percentage of fruit set increased. The differences observed in the effectiveness of ethephon in delaying bloom may be due to differences in spring temperatures during bud expansion. High temperatures during the period of bud expansion tended to accelerate bud development, minimizing the effect of treatment, whereas low temperatures during this period tended to accentuate treatment effects. GA3 applied in October delayed leaf senescence and abscission, but did not delay flowering.
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