The cut flower industry faces many challenges due to the difficulty in producing flowers with a long postharvest vase life. To ensure a longer vase life, growers must carefully regulate postharvest conditions and postharvest handling methods.
Water uptake is one of the most important factors in improving the length of vase life of cut flowers (Halevy and Mayak, 1979). As the leaves on the flowers transpire, water is drawn up through the xylem. If this process is impeded by a vascular blockage or accelerated by increased stomatal opening, transpiration will exceed uptake and water deficiency will occur. Thus, solutes are frequently added to vase solutions such as 8-hydroxyquinoline citrate (8-HQC), which can increase water uptake (van Doorn, 1997). To ensure quality product, rose growers, wholesalers, and retailers should understand the effects of additives or preservatives in vase solutions on rose vase life. While adding sucrose to a vase solution will increase vase life, it also allows increased bacterial proliferation that then requires the addition of antimicrobial compounds to vase solutions to minimize occlusions in the stem from bacteria. For example, the addition of 8-HQC to vase solutions reduced bacteria levels found in the bottom 5-cm segment of ‘Sonia’ rose stems from 840,000 cfu/g fresh weight to less than 120 cfu/g fresh weight (van Doorn, 1990). A low pH solution produced by the addition of sodium hypochlorite and a pH 3.0 buffer also reduced bacteria levels and increased water conductance in several rose cultivars (Marousky, 1971; van Doorn, 1990). Sucrose decreased water absorption in ‘Better Times’ roses; however, Marousky (1969, 1971) determined that sucrose extended vase life. In ‘First Red’, vase life increased over the control when held in a vase solution containing up to 1.5% sucrose and vase life declined with higher concentrations of sucrose up to 3% (Singh et al., 2003). Bhattacharjee (1994) found in a study on 10 rose cultivars that the use of a preservative solution containing 300 mg·L−1 8-HQC and 1% sucrose increased vase life vs. using distilled water. The extent of the increase varied by cultivar from 1.0 to 2.7 d. Ketsa et al. (1993) found that using a holding solution containing 5% sucrose and 20 mg·L−1 silver nitrate significantly improved the vase life of ‘Eiffel Tower’, ‘Swartmore’, and ‘Yankee’ roses, but did not improve vase life of ‘King’s Ransom’ or ‘Confidence’.
Ethylene, a naturally occurring plant hormone, is another postharvest factor that can negatively impact flower quality. Thus, some producers use antiethylene agents to minimize its effects (Dole and Wilkins, 2005). The effect of ethylene and antiethylene agents on cut rose flowers is varied and appears to be cultivar dependent. On a test with 38 cut rose cultivars, 1 μL·L−1 exogenous ethylene shortened vase life of 27 cultivars, impeded the rate of flower opening in six cultivars, and had no effect on five cultivars (Macnish et al., 2010). RueySong et al. (2001) noted that a 0.1- to 2-μL·L−1 exogenous application of ethylene significantly decreased vase life in ‘Golden Medal’ cut roses but had less of an effect on ‘Grand Gala’ vase life. Ethylene at 0.5 μL·L−1 inhibited (three cultivars), accelerated (14 cultivars), or had no effect (five cultivars) on flowering opening (Reid et al., 1989). For the effects of antiethylene agents, Reid et al. (1989) noted that STS could overcome the effects of exogenous ethylene. Singh et al. (2004) found that STS improved the vase life in three of seven rose cultivars tested, and Macnish et al. (2010) showed that STS could prevent an ethylene-induced drop in vase life in three ethylene sensitive cultivars.
Contrasting reports exist on the efficacy of 1-MCP. Philosoph-Hadas et al. (2005) found that treating stems with 0.4 μL·L−1 1-MCP for 4 h increased vase life for rose cultivars Pink Tango, Jazz, Frisco, and Golden Gate compared with ethylene-exposed control stems, and Macnish et al. (2010) found that various types of 1-MCP treatment prevented the negative effects of exogenous ethylene. However, Chamani et al. (2005) found that treating stems with 1 μL·L−1 1-MCP for 2 h did not improve vase life in ‘First Red’. The effects of ethylene and antiethylene agents on water uptake are also not known.
The application of postharvest research to the industry has always been a concern of researchers, and there appears to be limited information about how the number of stems per vase and recutting time impacts postharvest quality. Restrictions on availability of plant materials and time to collect data usually limit the number of stems per replication in research. Commercial cut flower growers, wholesalers, and retailers typically group rose stems in bunches of 10 or more and also place dozens of bunches in each bucket as the flowers are harvested, processed, and marketed. For postharvest evaluation, commercial tests are usually conducted using whole bunches with 10 or more stems, while university research often uses replications of one, three, or five stems per vase. Also, after receipt of roses, stems are usually recut to increase vase life (Dole and Wilkins, 2005). However, questions still remain about how changing drying time after recutting the stem, drying time before recutting the stem, and the amount of the stem recut impacts postharvest floral quality.
Therefore, the objectives of this research were to quantify the effects of 1) various vase solutions, 2) application of exogenous ethylene and antiethylene compounds before and after shipment, 3) stem number in a vase, and 4) postharvest dry storage on the postharvest performance of several cut rose cultivars.
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