Hyo Beom Lee

Inhibition of premature flowering by intermittent high temperature treatment to young Phalaenopsis plants

High temperature is required in commercial cultivation of Phalaenopsis plants to inhibit flowering until the plants can support the flower quality. However, maintenance of continuously high greenhouse temperature is costly. This study was conducted to develop a new cultivation strategy for preventing premature flowering by energy-saving flowering inhibition. In Experiment I, clones of Phalaenopsis ‘Hwasu 355’ grown in a greenhouse for 2, 4, and 8 months (2-, 4-, and 8-month-old) were subject to low temperatures of 25/20°C (day/night) for 0, 1, 2, 3, 4, 5, or 10 weeks. After each treatment, plants were transferred to high temperatures of 28/28°C. In addition, 8-month-old plants were treated with 7 weeks of low temperature to observe flower-stalk differentiation. In Experiment II, clones of 8-month-old Phalaenopsis ‘Hwasu 355’ and Doritaenopsis ‘Mantefon’ plants were cultivated at four different temperature regimes for 16 weeks: continuous low temperature, 1 week of high temperature for every 1 week of low temperature, 1 week of high temperature for every 2 weeks of low temperature, and 2 weeks of high temperature for every 2 weeks of low temperature. In Experiment I, ‘Hwasu 355’ plants younger than 4 months old were not mature enough to flower. 8-month-old plants treated with 4 or 5 weeks of low temperature showed 30% or 20% flower-stalk emergence, respectively. However, further flower-stalk elongation of these plants was inhibited after they were moved to 28/28°C conditions. In Experiment II, flower-stalk emergence was not observed in ‘Hwasu 355’ plants treated with intermittent high temperatures. However, ‘Mantefon’ plants showed flower-stalk emergence in all treatments. The percentage plants with visible inflorescences (flower-stalk longer than 0.5 cm) increased with increasing low temperature intervals between high temperature treatments. The number of days to visible inflorescence was increased with increasing total high temperature duration during cultivation. These results indicate that intermittent high temperature treatment can inhibit premature flowering in young Phalaenopsis plants. However, because the sensitivity among cultivars differs, modification of the treatment method is needed to more effectively inhibit premature flowering.