EFFECTS OF SUPPLEMENTARY LIGHTING AND BENDING TECHNIQUE ON GROWTH, FLOWERING AND CARBOHYDRATE STATUS OF ROSA HYBRIDA 'FRISCO'

Abstract

The effect of 2 supplementary lighting regimes (30 and 60 mu mol/m(2).s) and 2 cultural techniques (bending or decapitation) on the development of the new stems, dry-matter distribution and carbohydrate content of Rosa hybrida 'Frisco' plants was evaluated. Experiments were performed with single shoot rooted cuttings in a greenhouse compartment. Plants were grown at 18/16 degrees C day/night temperature and received a photoperiod of 18 hours. At each light level (30 and 60 mu mol/m(2).s) plants were randomly split in two groups depending on the harvesting technique. The primary shoot was either decapitated above the two most basal leaves with five leaflets or bended. Development of two shoots per plant was allowed. The analysis were performed on those two emerging shoots. The experiment was performed from January until March 1996, and was repeated for the decapitation treatment only, from March until May 1996. Bending of the primary shoot resulted in significant longer stems and increased flower stem weight and flower stem diameter with no effect of the supplementary lighting on the flower stem quality at harvest. For decapitated plants, however, a supplementary lighting of 60 mu mol/m(2).s reduced significantly the percentage of flower abortion, increased the flower stem development rate and the flower stem weight in comparison with 30 mu mol/m(2).s. The bending technique, in comparison to the decapitation method, results in faster shoot growth rate associated to higher glucose and fructose concentration in the apical part of the stem during the differentiation of the flower primordia and the shoot elongation phase.