EFFECT OF ROOT-ZONE AND AIR-TEMPERATURE ON FLOWERING AND GROWTH OF SPATHIPHYLLUM AND GUZMANIA-MINOR EMPIRE

Spathiphyllum and Guzmania, two flowering potplants were subjected to different root-zone temperatures up to 30-degrees-C on heated aluminium benches with a usual greenhouse temperature of 20-degrees-C or lower. The optimal air temperature for flowering of Spathiphyllum was 22-degrees-C, whereas root-zone temperatures in the range of 20-26-degrees-C were of less importance. Growth, development, plant height and leaf size of Spathiphyllum were enhanced by higher air temperatures up to 23-degrees-C. Elevated root-zone temperatures increased the shoot/root ratio and decreased the number of side shoots, but the dry weight per shoot was increased. Plant shape of Spathiphyllum can therefore largely be influenced by the root-zone and air temperature. Growth and development of Guzmania were enhanced by higher air temperatures up to 22-degrees-C. Both root-zone and air temperatures from 19 to 22-degrees-C promoted flowering without negative effects on the quality of inflorescences. Both crops can successfully be grown on heated benches, but root-zone temperatures above 26-degrees-C are not advisable for either crop. In both crops flowering is a temperature-sensitive process, which determines the optimal temperature settings of bench heating systems.