CULTIVAR DIFFERENCES IN TEMPERATURE DEMAND OF CUT CHRYSANTHEMUM

The influence of temperature on dry matter production, growth analysis parameters, stem length, number of leaves and flower characteristics of 25 cut chrysanthemum cultivars was investigated. Plants were grown in the greenhouse at two constant temperatures setpoints, 16 and 20ºC. Destructive measurements were carried out at the end of the long day period and at flowering. During the long day period relative growth rate was increased at high temperature for all cultivars due to an increase in net assimilation rate and for a few cultivars also by an increase in leaf area ratio. Significant temperature x cultivar interactions were only present for stem length, number of leaves and leaf area ratio. For all other characteristics there were clear differences between the two temperature treatments and the cultivars. Depending on the cultivar, flowering was delayed by 4 to 13 days when cultivated at low temperature. At flowering, a significant temperature x cultivar interaction was observed for all measured or calculated parameters. For example, for one cultivar both the differences in number of days till flowering and the total dry mass between 16ºC and 20ºC were small while for another cultivar there was a 34% higher dry mass at lower temperature, while the growth period was not much extended. Differences in dry mass at flowering between the two temperature treatments could be explained by differences in growth rate. These data show good possibilities for breeding for low temperature demand in cut chrysanthemum.