Heat injury thresholds in apples measured using chlorophyll fluorescence are influenced by orchard heat reduction technologies
Date
2008
Authors
Wand S.J.E.
Van Den Dool K.
Smit A.
Steyn W.J.
Journal Title
Journal ISSN
Volume Title
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Abstract
Chlorophyll fluorescence (Fv/Fm) was used to investigate thresholds of heat injury in apple fruit grown under orchard heat reduction technologies, i.e. evaporative cooling (EC) and 20% black shade netting. Picked apples were exposed to oven temperatures of 35, 40, 45, 50 or 55°C for two, four, six or eight hours and fruit surface temperature (FST) and Fv/Fm measured immediately following heat treatment, and after a 12-hour recovery period. In all trials, permanent injury occurred at 48-53°C FST irrespective of duration, with permanent injury possible at 42-47°C depending on duration. Non-EC 'Cripps' Pink' were more resistant to heat injury at 45°C than EC fruit. Fruit from three cultivars under netting ('Royal Gala', 'Fuji', and 'Cripps' Pink') had lower Fv/Fm at 43°C than non-netted fruit. The results indicate clear temperature thresholds for heat injury, with duration of exposure and orchard acclimation responses becoming important at sub-lethal surface temperature ofc.45°C.
Description
Keywords
Malus x domestica
Citation
Acta Horticulturae
772
772