INFLUENCE DE LA TEMPÉRATURE NOCTURNE ET D’UN APPOINT DE LUMIÈRE SUR LA CROISSANCE ET LE DÉVELOPPEMENT DU Gerbera ET DU Calendula

During fall-winter and spring conditions, Gerbera jamesonii H. Bolus ex Hook. ’Happipot’ and Calendula officinalis L. ’Fiesta Gitanas’ plants were subjected to night temperatures of 9, 13, 17 and 20 °C (1700–0800 h) during the first year of experiment and were grown under supplementary lighting treatments (control, 75 and 150 μmol m −2 s −1 ) for 7 h per day at a temperature of 13 °C during the second year. The plant top dry weight of gerbera increased with a rise in night temperature and supplementary lighting, but the reverse tendency was noted with calendula under the night temperature treatment; increases in plant top dry weight under supplementary lighting were observed only during the fall-winter period. For both species, root dry weight showed less variation than plant top dry weight under night temperature and supplementary lighting treatments. The percentage of gerbera plants having shoots increased with a reduction of the night temperature and supplementary lighting during the fall-winter experiments. The lowering of night temperature and supplementary lighting reduced calendula flower bud abortion only during the fall-winter period. For both species, flower number was not significantly different among die night temperature treatments. Supplementary lighting enhanced flower number of calendula only. Flowering of gerbera was accelerated with a reduction of night temperature and with supplementary lighting.Key words: Calendula officinalis, Gerbera jamesonii, night temperature, supplementary lighting