Combined effects of light and temperature on product quality of Kalanchoe blossfeldiana

A study with a comprehensive range of four constant photosynthetic photon flux densities (PPFD=60, 90, 140 and 200 mu mol m(-2)s(-1)) combined with four constant temperatures (18, 21, 23 and 26 degrees C; equal day and night temperature) was conducted in growth chambers using the pot plant Kalanchoe blossfeldiana. The current work allows for establishing relationships between these two climatic factors and product quality (plant height, number of flowering shoots, inflorescence size and inflorescence position) and cropping duration. From the studied product quality attributes, temperature and PPFD only showed a marked interaction on number of flowering shoots and on inflorescence size. The huge increase observed on the number of flowering shoots (from 4.6 to 20.5) was a response to higher PPFD, whereas temperature had only a minor effect. Inflorescence size was also enhanced at higher PPFD (especially at lower temperatures) but in contrast with the number of flowering shoots, inflorescence size was drastically reduced at higher temperatures. Plant height varied between 13.5 and 21.6 cm and was strongly influenced by temperature, whereas influence of PPFD was only marginal. Time to flowering decreased quadratically with temperature and with PPFD, and no interaction between these climatic factors was found. The fastest treatment (26 degrees C combined with 200 mu mol m(-2)s(-1)) was 30 days earlier than the slowest one (18 degrees C combined with 60 mu mol, m(-2)s(-1)). Different possibilities for reducing the cropping duration are proposed, taking product quality into account.