Temperature integration and DIF in cut chrysanthemum

Summary To reduce energy consumption in greenhouses, temperature integration can be used. However, the temperature integration principle considers only average temperatures and does not comply with the DIF concept (DIFference between mean day temperature and mean night temperature). With DIF, stem elongation, one of the major quality aspects of many crops, can be controlled. Short compact plants can be achieved by a negative DIF (average night temperature > average day temperature). In spring, summer and autumn temperature integration usually results in positive DIF and therefore longer stems. The aim of this study was to investigate whether temperature integration and DIF could be applied simultaneously. Greenhouse temperature fluctuates with temperature integration. During spring or autumn it is difficult to obtain short compact plants by a negative DIF with regular temperature integration. In this research, temperature integration was therefore modified by applying two independent integration regimes, one for daytime and one for nighttime while a zero DIF was set. Simulations and experiments with standard temperature control, regular and modified temperature integration showed that temperature integration and DIF could be applied simultaneously, while energy consumption and stem elongation were reduced.