EFFECTS OF TEMPERATURE INTEGRATION ON GROWTH AND DEVELOPMENT OF ROSES

Dutch horticulture aims at a reduction of the energy use in greenhouses by 65% in 2010 compared to 1980. When temperature integration is applied, temperatures may be reduced, as long as they are compensated by higher temperatures within a pre-set time span. Applying temperature integration without adverse effects on plant growth requires knowledge about critical temperatures. In this study, effects of temperature integration with bandwidths of 0, 6 and 10 °C (average temperature of 20 °C) and integration periods of 2 and 14 days on rose plants were investigated. Shoot lengths at the harvestable stage were reduced with increasing bandwidths. This reduction in shoot length became stronger as the integration period increased. The developmental rate of rose shoots to the harvestable stage was not affected by temperature integration. Shoot fresh weight decreased at a bandwidth of 10 °C, but not at a bandwidth of 6 °C. For the application of temperature integration in the practice of cut rose growing, shoot length development is the most critical process, since it partly determines the price of rose stems. If a certain reduction in stem length is acceptable to commercial rose growing, temperature integration with a bandwidth of 6 °C can be applied even at longer integration periods without affecting the developmental rate and shoot weight.