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  • Author or Editor: Iona E. O'Brien x
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The early growth responses of apple fruit to temperature were studied under controlled environment conditions. Growth of fruit on young trees of `Fuji'/M.9 `Golden Delicious'/M.9, and `Harold Red Delicious'/M.9 was frequently measured, over a 30-day period commencing 10 days after full bloom, under daily maximum/minimum temperatures of 22/12, 19/9, 16/6 and 13/3C. All other environmental conditions were maintained constant across all temperature treatments. Fruitlet diameter growth rate was approximately constant over the treatment period within each temperature regime and ranged from 0.24 mm day-1 at 13/3C to 0.85 mm day-1 at 22/12C. The growth responses to temperature were similar among cultivars but expansion rates were highest for `Fuji' and lowest for `Golden Delicious'. Cell division rates and durations, using flow cytometry, were measured over the treatment period and could be related to diameter growth rates. The impacts of temperature-induced differences in early fruit growth rates on final fruit sire will be described.

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