Effect of Photoperiod on the Flowering of Some Cultivars of Hydrangea (<i>Hydrangea macrophylla</i>)

Abstract

The experiment was conducted in Hama governorate (Bammraa village) in Syria during the spring and summer seasons 2013-2014 to study the effect of photoperiod on some production indicators (Date of flowering, Number of flower clusters, Number of flowers, Diameter of flower cluster and length stem). Floral induction of three Hydrangea macrophylla . Ser cultivars (Mme. Emile Mouillere, Nikko Blue, Pia was evaluated to determine the flowering. Plants were tested under either natural day length (ND) or 24-hours-extended day(ED) or 8-hours short day (SD). Floral induction of H. macrophylla occurred under all treatments but was more rapid under ED. Number of flower clusters, flower numbers and diameter of flower cluster were significantly different for cultivars and photoperiods. Floral initiation and development were observed among photoperiods. Results indicated that ED was the best in all production indicators (Number of flower clusters, Number of flowers, Diameter of flower cluster and length stem) in the cultivars with significant differences. In addition, the results showed that the cultivar (Nikko blue) was more responsive in all production indicators but, the amount of anthocyanin was more in deep pink sepals than blue sepals.