EFFECTS OF CO2 ENRICHMENT AND DIFFERENT DAY NIGHT TEMPERATURE COMBINATIONS ON GROWTH AND FLOWERING OF ROSA L AND KALANCHOE-BLOSSFELDIANA V POELLN

The effects of increasing the CO2 concentration from 350 to 700-mu-l l-1 on growth and flowering of Rosa L. and Kalanchoe blossfeldiana at four different day/night temperature combinations (20/20-degrees-C, 23/14-degrees-C and 17/26-degrees-C day/night, and 20/20-degrees-C with 2 h at 14-degrees-C in the morning) were studied in 16 growth chambers. An increase in the CO2 concentration resulted in enhanced total dry weight, stem: leaf fresh weight ratio, flower fresh weight, length and diameter of the rose shoot, while the number of days until flowering was not affected. With the 17/26-degrees-C treatment, rose shoots were 3-4 cm shorter, and with the 23/14-degrees-C treatment flowering occurred about 2 days earlier than with the other temperature treatments. The results were the same for Rosa cultivars 'Frisco' and 'Kiss'. No significant interactions between CO2 and temperature were found. Plant dry weight and fresh weight of flowers in Kalanchoe were generally enhanced by CO2 enrichment. The effects of CO2 on dry weight, plant height and flower stem length were greater with the 23/14-degrees-C treatment compared with the effects of the other temperature treatments. A constant temperature (20/20-degrees-C) and the 23/14-degrees-C treatments gave the shortest and tallest plants, respectively.