Growth Responses and Flowering of <i>Kalanchoe</i> Cultivars under Elevated CO<sub>2</sub> Concentration and Varying Daylength

Abstract

This experiment was conducted to identify the morphological characteristics of elevated atmospheric CO2 concentration of Kalanchoe blossfeldiana cultivars under different daylength treatments, in order to apply the carbon reduction method. CO2 treatment took place between 22:00 and 04:00 with an average of 400 μmol·mol-1 (control) and 800 μmol·mol-1 on Kalanchoe blossfeldiana ‘Lion’ and ‘Fikalrudak’. The photoperiod was controlled using an 8 h (08:00 to 16:00), 12 h (06:00 - 18:00), and 16 h (04:00 - 20:00) light-dark cycle. The number of leaves increased more in plants under the 800 μmol·mol-1 treatment than those in the control, with a photoperiod of 8 h and 12 h in both K. ‘Lion’ and 8 h in K. ‘Fikalrudak’. Plant height was lower in plants treated with 800 μmol·mol-1 CO2 than under the control treatment with an 8-h photoperiod of 8 h, regardless of K. blossfeldiana cultivars. In K. ‘Lion’, immature leaf length and width increased more in plants treated with 800 μmol·mol-1 CO2 than in the control, with a photoperiod of 8 h and 12 h. However, the leaf length and width of K. ‘Fikalrudak’ was not affected by CO2 concentration. The nodes were produced primarily by increasing CO2 concentration to 800 μmol·mol-1, regardless of daylength and K. blossfeldiana cultivars. Flowering time was not affected by daylength, however, K. ‘Lion’ bloomed within the photoperiod of 8 h and 12 h and K. ‘Fikalrudak’ bloomed only under a photoperiod of 8 h. K. blossfeldiana cultivars bloomed effectively under less light availability, regardless of CO2 concentration. These results showed that a CO2-rich enrichment promotes leaf and node production of Kalanchoe blossfeldiana cultivars under short-day conditions. Since high concentration of CO2 enrichment can have an adverse effect on flowering quality, appropriate CO2 enrichment methods for the developmental stage and cultivars should be applied on a case-by-case basis.