855 Effects of Low O 2 on Cut Rose Flowers at Suboptimal Temperature M. Devecchi 1 and U. van Meeteren H. de Wild and E. Woltering Horticultural Production Chains Group Agrotechnological Research Institute Plant Sciences-Wageningen University P.O. Box 17 Marijkeweg 22, 6709 PG Wageningen 6700 AA Wageningen The Netherlands The Netherlands 1 On leave from Dipartimento di Agronomia University of Turin Via L. da Vinci 44, Grugliasco Italy Keywords: Controlled atmosphere, vase life, flower opening, respiration, ethylene production, petal enlargement, differential growth Abstract There is no commercial application of modified atmosphere storage or packaging for cut flowers. The reason for that would be that the most decisive factor for keeping quality is a low temperature during storage and transport. In practice, however, this low temperature is not always realised. However it is worthwhile knowing potential quality benefits that may arise from the use of modified O 2 and/or CO 2 concentrations at sub-optimal temperatures. Experiments have been conducted on cut rose flowers ‘First Red’ to study the effect on postharvest physiology of different O 2 partial pressures (0.5-21 kPa) during 5 days at 12 °C. During this period of transport simulation at different O 2 partial pressures, respiration rate and ethylene production of the flowers was measured. During subsequent flower opening during vase life, diameter and longevity of the flowers were recorded. Fresh weight and area of single petals were measured daily. Growth during vase life of the inner and outer petal surfaces was estimated. Oxygen uptake rate and ethylene production were logarithmically related to O 2 partial pressure. To lower oxygen uptake rate to less than 50% of that in air, a partial pressure of O 2 should be <2 kPa. However, in the O 2 range <2 kPa the R(espiratory) Q(uotient) indicated anaerobic respiration. Vase life was not significantly affected by O 2 concentrations during a 5 day storage period. Low O 2 partial pressures during storage resulted in poor flower opening afterwards. Petal growth was not inhibited by low O 2 -storage, but outer petals showed a greater increase in surface area and fresh weight after storage at 1 kPa O 2 than at higher O 2 partial pressures. Poor flower opening was the result of an increase in cell size at the upper region of the outer petal layer, which hampered outward reflex of the petals. INTRODUCTION The growing worldwide importance of cut flower production in regions far from major markets has created the need to improve conveyance and package systems for flower products, so as to assure satisfactory qualitative standards. According to the review of Goszczynska and Rudnicki (1988) Controlled Atmosphere (CA) storage and Modified Atmosphere Packaging (MAP) are promising techniques for storage of cut flowers. Meir et al. (1995) reported improved keeping quality of mini-gladiolus spikes by MAP. However, there is no commercial application of CA or MAP for cut flowers. In contrast to vegetable and fruit produce, data available in the literature on the use of CA for cut flowers are scarce. Probably the reason for that is that the most decisive factor to maintain appropriate quality for the consumer is a low temperature (just above freezing point) during storage and transport (Reid, 2001a). Proc. XXVI IHC – Issues and Advances in Postharvest Hort. Ed. R.K. Prange Acta Hort. 628, ISHS 2003 Publication supported by Can. Int. Dev. Agency (CIDA)