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Determining the optimal nighttime air temperature for Phalaenopsis during the vegetative stage

Boekbijdrage - Boekhoofdstuk Conferentiebijdrage

Daytime air temperatures above 26 degrees C inhibit flower initiation of Phalaenopsis regardless of the nighttime air temperature. This opens possibilities for energy saving by lowering the nighttime air temperature during the vegetative growth phase. As chilling injury can occur after a few hours exposure to cool temperature conditions, growers prefer to cultivate Phalaenopsis at daily temperatures between 25 and 30 degrees C. A better understanding of the low night temperature effects on the photosynthetic physiology of Phalaenopsis would improve production of these orchids in terms of greenhouse temperature control and energy use. Therefore, the Phalaenopsis hybrid 'Hercules' was subjected to nighttime air temperatures of 27.0, 24.0, 21.1, 18.0, 15.4 and 12.8 degrees C, while during the day temperatures of about 27.5 degrees C were maintained. Photoperiod was set to 9 h with non-saturating white fluorescent light (217.3 +/- 2.8 mu mol PAR m(-2) s(-1)). The chlorophyll fluorescence temperature response curves revealed a significant reduction of the photochemical quenching (qP) and quantum efficiency of PSII electron transport (Phi(PSII)) when plants were exposed to night temperatures below 21.1 degrees C, but maximum quantum yield of PSII photochemistry (F-v/F-m) suggested no PSII damage for these night temperatures. Early morning determined leaf acidity, which can be used as a measure of nocturnal malic acid production, and leaf water potential were lowest at night temperatures of 21.1 and 24.0 degrees C. However, maximum net CO2 uptake in the late night (2 h before daytime) was observed between 15.4 and 21.1 degrees C. Furthermore, PSII photochemistry required only 5 h for full recovery of all night temperatures imposed. Our results suggest that Phalaenopsis can tolerate relatively cool night temperatures during the vegetative growth stage.
Boek: Acta Horticulturae
Volume: 893
Pagina's: 865 - 871
Jaar van publicatie:2011