Temperature and Postharvest Performance of Rose (Rosa hybrida L. ‘First Red’) and Gypsophila (Gypsophila paniculata L. ‘Bristol Fairy’) Flowers

The respiration of cut flowers of rose (Rosa hybrida L. ‘First Red’) and gypsophila (Gypsophila paniculata L. ‘Bristol Fairy’) increased exponentially with increasing respiration, with a Q10 value between 0 and 10°C of 3 for both flowers. The vase life of the flowers was negatively affected by simulated transport at higher temperatures whereas dry storage for 5 days at 0°C resulted in a vase life that was not distinguishable from that of the initial controls. When ‘First Red’ flowers were held in wet storage, the effects of temperature on vase life were quite similar, with slightly longer vase life for wet-stored flowers from 12.5 and 15°C. We found a highly significant linear relationship between respiration during storage and vase life after storage for these important commercial crops, indicating the importance of maintaining temperatures close to the freezing point during commercial handling and transport in contrast to common belief in the industry. INTRODUCTION Roses and gypsophila are important standard materials in the florist trade. Although it has long been asserted that flowers should be stored and transported at temperatures close to the freezing point (Maxie et al., 1973; Carow, 1978; Hardenburg et al., 1986; Nowak and Rudnicki, 1990; Jones and Moody, 1993; Sacalis, 1993), it is only recently that the importance of storage temperature in the vase life of stored flowers has clearly been demonstrated (Cevallos and Reid, 2000; Çelikel and Reid, 2002). A common assertion by producers of cut roses is that storage at temperatures near 0°C results in blackening of red cultivars like ‘First Red’. This, and the perception that storage temperature is not particularly critical, especially if flowers are transported in water, has led to temperatures that are higher than desirable during long-distance flower shipment and storage in wholesale warehouses. The objective of the experiments reported here was to examine the hypothesis that postharvest performance of red roses and gypsophila would be optimal when the flowers were stored at temperatures just above the freezing point. MATERIALS AND METHODS Plant Material Roses (Rosa hybrida L. ‘First Red’) were obtained from a commercial grower in Watsonville, transported to Davis, and used in experiments within 24 h. Gypsophila (Gypsophila paniculata L. ‘Bristol Fairy’) were grown in California and obtained from a local wholesale distributor. Respiration Measurement The effect of temperature (ranging from 0 to 20°C) on respiration was determined using the ‘dynamic’ system described by Cevallos and Reid (2000), in which we followed respiration of the flowers over the whole temperature range. A single rose flower, cut just 1789 Proc. 5 Int. Postharvest Symp. Eds. F. Mencarelli and P. Tonutti Acta Hort. 682, ISHS 2005 below the receptacle, was sealed in a jar ventilated with a stream of CO2-free air flowing at a rate sufficient to prevent CO2 concentrations rising above 500 ppm at the highest temperature used (20°C). The jar was submerged in a 30% glycol bath (LAUDA K-4/R, Brinkmann Instruments, Germany) providing precise control of temperature. Respiration of the flower was determined by continuously recording the CO2 concentration at the outlet of the jar using an infrared gas analyzer (Qubit Systems Inc., Kingston, Ontario, Canada). The flowers were held overnight at 20°C in the respiration chamber to dissipate any effects of handling on respiration. The CO2 concentration was recorded, then the temperature of the bath was changed to 15°C. After a stable CO2 reading was obtained (approximately 1.5 hours), the temperature of the bath was further reduced to 12.5°C, and after similar time intervals to 10, 7.5, 5, 2.5, and 0°C. The effect of temperature on respiration was measured in this manner for at least three replicate flowers. For gypsophila, respiration was measured on a group of panicles comprising buds and open flowers. For rose, we used a single flower cut to 6 cm of the stem. Wet and Dry Storage To determine the effect of storage temperature on subsequent vase-life at 20°C, flowers were recut to a length of 30 cm, and six replicate stems were wrapped in newspaper and polyethylene and packed dry in a fiberboard box. Replicate stems of ‘First Red’ roses were also placed in vases containing DI for ‘wet’ storage. The flowers were then stored at temperatures ranging from 0°C to 12.5°C for five days. Determination of Vase Life After storage, the roses were re-cut under water to 25 cm and placed in DI containing 50 ppm NaOCl (chlorine bleach), in the controlled-environment vase life evaluation room. A 20 cm panicle was removed from each gypsophila inflorescence and placed in the same solution. The room was kept at 20°C and about 60% relative humidity. Artificial light (15 μmol.m.sec PAR) was provided 12 hours/day from cool white fluorescent tubes (Sylvania Lighting Co., Danvers, Mass.). The flowers were examined daily, and their vase life was recorded as the time to wilting of the flower (roses), or wilting of half of the open florets (gypsophila).