Flowering responses of Petunia plants to photoperiod and irradiance

Abstract

Various flowering responses in Petunia X hybrida Vilm. 'Garden Party White' and 'Snow Cloud White' were studied under different photoperiods and irradiance levels. In particular, leaf number below the first flower bud (LNBFB) on the main stem, time to macroscopic flower bud visibility (MFBV), time to anthesis, time to flower bud development, and the percentage of flower bud abortion were examined. LNBFB increased significantly (P<0.001) only under a combination of short-day (SD) and low irradiance, but each had little effect alone. Time to MFBV and time to anthesis decreased, as photoperiod or irradiance increased. One of the main factors on late anthesis under unfavourable light condition appears to be flower bud abortion. In this study, photoperiod or irradiance had no effect on LNBFB, but they influenced the time to anthesis either singly or together, indicating that long-day (LD) and/or high irradiance is necessary for minimizing a production period of petunia plants.