Supplementary lighting regimes strongly affect the quantity of gerbera flower yield

Three experiments were conducted between November and April during years 1994-1997 to investigate the effects of photoperiod, supplementary light intensity and daily supplementary light integral on gerbera (Gerbera x cantabrigensis Lynch cvs. Estelle and Ximena) flowering in poor natural light conditions. The plants were subjected to different photoperiods (12, 18 and 24 h), light intensities (75, 112.5, 150 and 300 mu mol/m(2)s PAR) and supplementary lighting periods (12, 18 and 24 h). In all experiments the 12-h photoperiod produced the highest number of inflorescences if the same daily supplementary light integral was used. Doubling the daily light integral by extending the photoperiod to 24 h did not increase the flower yield except in the case of 'Estelle' in one experiment. On the other hand, an increase in the daily light integral by increased supplementary light intensity affected strongly the number of inflorescences in the 12-h photoperiod. As the quantity of gerbera flower yield is strongly affected;by supplementary lighting regimes, grower must be aware of that different distributions of same light energy over one day may lead to a change of about 45 % in number of inflorescences. If only the number of inflorescences is considered, a combination of short photoperiod and high light intensity can be recommended.