Inhibition of inflorescence initiation in immature Doritaenopsis Queen Beer ‘Mantefon’ by photoperiod and temperature

Abstract

Inflorescences of Doritaenopsis are commonly induced when the plants are exposed to temperature below 26°C. They need to maintain temperature above 28°C for maintaining the vegetative growth stage and inhibiting inflorescence initiation. We investigated the effects of photoperiod on inflorescence initiation in immature Doritaenopsis at floral inductive temperatures in order to determine an alternative method to prevent inflorescence initiation and to reduce heating expenses. Six-month-old Doritaenopsis Queen Beer ‘Mantefon’ was grown under 9/15 hours (SD), 12/12 hours (MD), 16/8 hours (LD), or SD with night interruption (NI: 22:00–02:00 HR) at 21 or 26°C in module boxes inside a growth chamber. The maximum irradiance was 100 ± 10 and 4 ± 1 μmol·m⁻²·s⁻¹ during the day and NI, respectively. Inflorescence of the plants was completely inhibited when the plants were grown at 26°C, whereas the plants grown at 21°C could not inhibit inflorescence initiation. However, percent visible inflorescence was reduced greatly in LD when the plants grown at 21°C. NI also reduced visible inflorescence. The LD delayed days to visible inflorescence, followed by MD, NI, and SD when the plants were grown at 21°C. The number of new leaves and leaf span were increased in the plants grown at 26°C more than those grown at 21°C. The plants grown under LD at 21°C had a similar number of new leaves compared to the plants grown at 26°C until 17 weeks of treatment. These results indicated that LD or NI could be an alternative method to high temperature above 26°C for inhibiting inflorescence initiation in immature Doritaenopsis ‘Mantefon’ and could thus save heating costs.