Combined effects of root and night air temperatures on the growth and mineral nutrition of cucumber. I. The effect on growth.

Abstract

Growth responses of young cucumber plants (Cucumis sativus L.) to various root and night air temperature combinations were determined. Seedlings were grown hydroponically in a growth chamber at different root temperatures (13°, 18°, 23° and 28°C) and air temperatures in the night (12°, 17° and 22°C) . Daytime air temperature was maintained at 27°C. A combination of 28°C root temperature and 22°C night air temperature gave the maximum growth rate. Irrespective of night air temperature, a higher root temperature resulted in a higher growth rate. However, the root zone warming was less effective in growth promotion when combined with lower night air temperatures, mainly due to a decrease in its efficiency of increasing leaf area. These results suggest that in cucumber, in the early vegetative growth stage, an increase in root temperature does not increase growth rate to an extent that can compensate the growth reduction caused by low air temperature in the night.