The Effect of Photoperiod and Temperature on Flowering of Pycnosorus Thompsonianus

The flowering responses of Pycnosorus thompsonianus to day-lengths and temperatures were investigated to study the floral regulation of this potential ornamental plant in southern Queensland, Australia. Plants of different treatments were cooled at 20/10°C or kept at 30/20°C for 21 or 42 days under short day (SD), long day (LD), or short day for six weeks before transferring to long day (SDLD) in environment-controlled greenhouse bays during 2009 - 2010. LDs promoted earlier flowering and plants under LDs flowered regardless of temperature regimes. Cool temperatures and cooling periods were required for efficient flowering of plants under SDs, but were not important for plants under LDs and SDLDs. Forty-two percent of the plants under warm (30/20°C) SD remained vegetative after a 16-week growing period. Cooling for 21 days was sufficient for plant growth and floral development of the species. Daylength was more effective than temperatures for promoting earlier flowering and for increasing flower production.