1 Exogenous sucrose effects on carbohydrate level, flower respiration and longevity of potted miniature rose (Rosa hybrida) flowers during postproduction. José A. Monteiro a✶ ,Terril A. Nell b and James E. Barrett b a F.E.R.N., University of Algarve, 8000-117 Faro, Portugal b Environmental Horticulture Department, University of Florida, Gainesville, FL 32611, USA Abstract The effect of continuous injection of exogenous sucrose on single flower postproduction longevity of attached flowers of potted ‘Meijikatar’ miniature roses was studied. At bud showing color, with sepals starting to unfold, plants were moved to interior conditions and started being continuously injected with a solution of 3% sucrose or distilled water. Carbohydrate levels, flower respiration and single flower longevity were assessed. The method presented some variability in the amounts of solution supplied to the plants. Infusion of exogenous sucrose increased attached miniature rose flower longevity by 1.5 days and also increased flower respiration rate. The higher the uptake rate of sucrose solution the longer the flowers lasted. Exogenously supplied sucrose was consumed by increased respiration and consequently, at day 6 after anthesis, no differences were found in nonstructural carbohydrate levels between water and sucrose treatments. However, stem percent of soluble sugars was ✶ Corresponding author. Tel. 351-289-800966, fax:351-289-818419. E-mail address:jmontei@ualg.pt (J.A. Monteiro) Florida Agricultural Experiment Station journal series nº R-07388.