Effects of day and night air temperature on growth, productivity and energy use of long English cucumber

To determine the optimum air temperature regime for greenhouse seedless cucumber production under North American conditions, the cvs. Corona (in the spring of 1990 and 1992) and Aramon (in the spring of 1992) were grown under nine day/night temperature regimes composed of a factorial combination of three day (18, 21 and 24 °C; DT) and three night (16, 18 and 20 °C; NT) heating temperatures, at a common 24 °C ventilation temperature. Plant development rates (leaf and flower number) were linearly increased with increasing daily average air temperature (MT), but not affected by day–night air temperature difference (DIF), indicating that plant development rates increased with increasing air temperature regardless of DT or NT. Specific leaf weight decreased with increasing DT or NT, and leaf photosynthesis rates decreased with increasing DT. Therefore, high DT or NT promoted the growth rates of young cucumber plants mainly through increasing leaf area ratios. Early and final yields of Corona were mainly affected by MT, not by DIF, while early and final yields of Aramon were mainly increased by DIF. Fruit size increased with increasing MT. Optimum MT for Corona fruit production was 19 °C heating temperature, at a 24 °C ventilation temperature. Optimum day/night air temperature regime for Aramon fruit production was at 21/16 °C day/night heating temperature, at a 24 °C ventilation temperature. Key words: Cucumis sativus, growth, yield, fruit size, daily average air temperature, day-night air temperature difference