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Ria T. Leonard and Terril A. Nell

Several pulse solutions were tested for their effectiveness in preventing leaf senescence on four cut oriental lily cultivars (Lilium sp. `Acapulco', `Kissproof', `Noblesse' and `Star Gazer'). Stems were pulsed 24 hours after harvest for 1 hour, stored in boxes in the dark for 5 days at 3 °C (37.4 °F) then evaluated in postharvest conditions. A new commercial product called Chrysal BVB, a proprietary mixture manufactured by Pokon & Chrysal (Miami) containing cytokinine and gibberellic acids, was the most effective product tested. Chrysal BVB [1 mL·L–1 (0.1%)] prevented leaf chlorosis and abscission on `Acapulco' and `Noblesse' and significantly reduced it by 82% on `Star Gazer' and by 69% on `Kissproof'. Stems pulsed in Fascination, a commercial mixture containing 1.8% gibberellins (GA4+7) and 1.8% benzyladenine [5.4 mg·L–1 (ppm) each], virtually prevented leaf chlorosis on `Noblesse', reduced it by 50% or more on `Acapulco' and `Star Gazer', and significantly delayed it 8 days on `Kissproof'. A 10 μm (2 ppm) pulse in thidiazuron, a substituted phenylurea with cytokinin-like properties, delayed leaf chlorosis on `Star Gazer' but to a lesser extent compared to BVB and Fascination. Chrysal SVB, a propri-etary mixture manufactured by Pokon & Chrysal containing gibberellic acid, had no effect on reducing leaf chlorosis on `Star Gazer'. None of the pulse solutions had adverse effects on bud opening, flower quality or vase life. Maintaining stems in a bulb flower preservative significantly reduced leaf chlorosis and abscission in all cultivars when stems were not pretreated with a pulse solution or when a pulse solution was ineffective.

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Andrew J. Macnish, Ria T. Leonard, and Terril A. Nell

The vase life of many cut flowers is often limited by bacterial occlusion of stem bases. In this study, we tested the efficacy of a novel antimicrobial agent, aqueous chlorine dioxide (ClO2), to extend the longevity of cut Gerbera flowers by reducing the number of bacteria in vase water. Commercially mature and freshly cut Gerbera jamesonii `Monarck' flowers were placed into clean vases containing deionized water and 0, 2, 5, 10, 20, and 50 μL·L-1 ClO2. Stems were then maintained in solutions at 21 ± 0.5 °C and 42 ± 11% relative humidity until the end of vase life. Inclusion of 2, 5, and 10 μL·L-1 ClO2 in vase water had beneficial effects on flower longevity. For instance, treatment with 5 and 10 μL·L-1 ClO2 extended flower longevity by 1.4-fold or 3.7 days, as compared to control flowers (0 μL·L-1 ClO2). In contrast, exposure to the higher concentrations of 20 and 50 μL·L-1 ClO2 did not extend flower vase life. Relative to control flowers, treatment with 10 μL·L-1 ClO2 delayed the onset of detectable bacterial colonization of vase solutions from day 3 to day 6 of vase life. However, this ClO2 treatment did not reduce the number of bacteria that subsequently accumulated in vase water as compared to control flowers. Treatment with 10 μL·L-1 ClO2 also increased rates of solution uptake by stems and reduced the loss of flower fresh weight over time. These results highlight the potential use of ClO2 treatments to extend the postharvest longevity of Gerbera flowers.

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Andrew J. Macnish, Ria T. Leonard, and Terril A. Nell

Exposure to 0.1, 1.0, or 10 μL·L−1 ethylene for 4 days at 21 °C reduced the display life of 17 commonly traded potted foliage plant genotypes (Aglaonema ‘Mary Ann’, Anthurium scherzerianum ‘Red Hot’ and ‘White Gemini’, Aphelandra squarrosa ‘Dania’, Chlorophytum comosum ‘Hawaiian’, Codiaeum variegatum pictum ‘Petra’, Dieffenbachia maculata ‘Carina’, Dracaena marginata ‘Bicolor’ and ‘Magenta’, Euphorbia milii ‘Gaia’, Euphorbia splendens ‘Short and Sweet’, Ficus benjamina, Polyscias fruticosa ‘Castor’, Radermachera sinica ‘China Doll’, Schefflera elegantissima ‘Gemini’, Schefflera arboricola ‘Gold Capella’, Spathiphyllum ‘Ty's Pride’). Ethylene treatment hastened leaf and bract abscission or senescence. The responsiveness of plants to ethylene varied considerably; six genotypes were sensitive to 0.1 μL·L−1 ethylene, whereas three genotypes required exposure to 10 μL·L−1 ethylene to trigger visible injury. Four genotypes (Asplenium nidus, Chamaedorea elegans ‘Neathe Bella’, Hedera helix ‘Chicago’, Syngonium podophyllum ‘White Butterfly’) included in our study were insensitive to ethylene. Treating Aglaonema ‘Mary Ann’, Polyscias fruticosa ‘Castor’, and Schefflera arboricola ‘Gold Capella’ plants with 0.9 μL·L−1 1-methylcyclopropene (1-MCP, provided as EthylBloc™), a gaseous ethylene-binding inhibitor, for 4 to 5 h at 21 °C reduced the deleterious effects of ethylene. The release of 1-MCP from two sachets containing EthylBloc™ into a single shipping box also protected Aphelandra squarrosa ‘Dania’, Euphorbia milii ‘Gaia’, Polyscias fruticosa ‘Elegans’, and Schefflera arboricola ‘Gold Capella’ plants from ethylene injury after simulated transport. Our data reveal the genetic variation in ethylene sensitivity among potted foliage plants and highlight genotypes that benefit from 1-MCP treatment.

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Terril A. Nell, James E. Barrett, and Ria T. Leonard

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Andrew J. Macnish, Ria T. Leonard, and Terril A. Nell

The postharvest longevity of fresh-cut flowers is often limited by the accumulation of bacteria in vase water and flower stems. Aqueous chlorine dioxide is a strong biocide with potential application for sanitizing cut flower solutions. We evaluated the potential of chlorine dioxide to prevent the build-up of bacteria in vase water and extend the longevity of cut Matthiola incana `Ruby Red', Gypsophila paniculata `Crystal' and Gerbera jamesonii `Monarch' flowers. Fresh-cut flower stems were placed into sterile vases containing deionized water and either 0.0 or 2 μL·L–1 chlorine dioxide. Flower vase life was then judged at 21 ± 0.5 °C and 40% to 60% relative humidity. Inclusion of 2 μL·L–1 chlorine dioxide in vase water extended the longevity of Matthiola, Gypsophila and Gerbera flowers by 2.2, 3.5, and 3.4 days, respectively, relative to control flowers (i.e., 0 μL·L–1). Treatment with 2 μL·L–1 chlorine dioxide reduced the build-up of aerobic bacteria in vase water for 6 to 9 days of vase life. For example, addition of 2 μL·L–1 chlorine dioxide to Gerbera vase water reduced the number of bacteria that grew by 2.4- to 2.8-fold, as compared to control flower water. These results confirm the practical value of chlorine dioxide treatments to reduce the accumulation of bacteria in vase water and extend the display life of cut flowers.

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Terril A. Nell, Ria T. Leonard, and James E. Barrett

Postproduction characteristics of the new poinsettia cultivar `Freedom', as influenced by production and postproduction treatments, were evaluated. In one study, plants were grown under three production irradiance levels consisting of 450, 675 or 900 μmol s-1m-2 at 18/24C or 22/28C night/day temperatures and moved at anthesis to postproduction conditions (10 μmol s-1m-2 for 12 hr/day, 21±2C). Anthesis was delayed, plant height and diameter decreased, and a reduction in the number and development of cyathia occurred when maintained at low production temperature and irradiance. Leaf drop, which was minimal after 30 days postproduction (< 25%), was unaffected by production treatments, while cyathia drop was accelerated by low production irradiance and temperature, but not reduced after 30 days.

Leaf retention and quality in postproduction conditions are excellent. Cyathia drop averages 40 to 50% after 2 weeks in postproduction conditions. Bracts and leaves maintain their color well, with only slight fading after 30 days. Plants exhibit slight epinasty after shipping, but recover within a couple of days. These characteristics of `Freedom' make it a promising variety for the future.

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Terril A. Nell, Ria T. Leonard, and James E. Barrett

Production irradiance levels on growth, light compensation point (LCP), dark respiration (DR), and interior longevity of potted chrysanthemum (Demfranthema grandiflora Tzvelev. cvs. Iridon and Mountain Peak) and poinsettia (Euphorbia pulcherrima Wind. cvs. Annette Hegg Dark Red and Gutbier V-10 Amy) were determined. LCP and DR were measured at anthesis and during acclimatization to interior conditions (10 μmol·s-1·m-2). Days to flowering, inflorescence diameter, total chlorophyll, and interior longevity of chrysanthemum increased when maintained at a mean maximum photosynthetic photon flux density (PPFD) of 500 μmol·s-1·m-2 compared to plants shifted to 300 or 100 μmol·s-1·m-2 8 weeks after planting. LCP and DR were highest at anthesis and were reduced 38% and 49%, respectively, for chrysanthemum and 19% and 42%, respectively, for poinsettia within 3 days in interior conditions. Chrysanthemum plants shifted to 300 μmol·s1·m-2 during production had lower LCP and DR rates at anthesis and throughout time in interior conditions compared to plants maintained at 500 μmol·s-1·m-2. The acclimatization of chrysanthemum to reduced production PPFD is of little significance because interior longevity is reduced. No differences were found in the LCP or DR of poinsettia or chrysanthemum cultivars that differ in interior performance, demonstrating that these physiological characteristics are not good indicators of interior longevity for chrysanthemum and poinsettia.

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Ria T. Leonard, Amy M. Alexander, and Terril A. Nell

This study examined three transport systems used to transport fresh, non-stored cut flowers from Bogotá, Colombia, to the United States on a monthly basis for 1 year. Five cultivars of cut rose (Rosa hybrida), alstroemeria (Alstroemeria peruviana), carnation (Dianthus caryophyllus), and gerbera (Gerbera jamesonii) were commercially transported using a 7-day conventional distribution system with temperature controls and two rapid transport systems (3-day or 24-hour) with little or no temperature controls, respectively. Temperatures during the 24-hour transport system increased steadily and temperatures were at or above 10 °C for ≈18 h, with half of that time above 15 °C for all shipments. The 3- and 7-day systems had temperature fluctuations ranging from 3 to 24 °C and 3 to 19 °C, respectively. Flowers transported using the rapid transport systems had a significantly longer vase life compared with the 7-day transport in 83% of the shipments of alstroemeria and roses, in 58% of the shipments of carnations, and in 50% of the shipments of gerberas. Vase life increased 5.6% to 17.1% (0.7 to 2.1 days) for roses, 3.2% to 16.7% (0.5 to 2.7 days) for alstroemerias, 12.8% to 34.6% (1.1 to 6.2 days) for gerberas, and 4.6% to 8.8% (1.1 to 2.3 days) for carnations when using the rapid transport systems compared with the 7-day transport system. Some cultivars were more tolerant of the longer transport. The results show that when using fresh, non-stored flowers, the rapid transport systems had equal or longer vase life than the 7-day transport system in the majority of shipments for each flower species. Results also demonstrate that better temperature management during transport is a critical issue in the floral industry that needs to be improved upon.

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Terril A. Nell, Ria T. Leonard, A.A. De Hertogh, Lena Gallitano, and James E. Barret

Postproduction evaluations of two cultivars each of Amaryllis (Hippeastrum), calla lily, Freesia, lily, and paperwhite Narcissus were conducted under postproduction temperatures of 18, 21 and 24C and irradiance levels of 7 or 14 μmol·m-2·s-1. Amaryllis longevity ranged from 10 to 24 days, with an increase of 7 to 10 days at 18C. Excessive stem elongation occurred and was greatest at 24C. Calla lily longevity ranged from 33 to 68 days, with up to a 25-day increase at 18C and 14 μmol·m-2·s-1. Freesia lasted 24 to 33 days with an increase of 6 to 9 days at 18C. Leaf yellowing and stalk elongation was a common problem of Freesia, especially at 24C. Lilies lasted 17 to 31 days, with an increase of 9 to 11 days at 18C. Asiatic lilies were superior to Oriental lilies. Paperwhite Narcissus lasted 13 to 27 days, increasing up to 10 days at 18C. Cultivar differences in longevity and quality were observed. Optimum postproduction conditions ranged from 18 to 21C at an irradiance of 14 μmol·m-2·s-1 for best quality and longevity.

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Andrew J. Macnish, Ria T. Leonard, Ana Maria Borda, and Terril A. Nell

Natural variation in the postharvest quality and longevity of ornamental plants can often be related to differences in their response to ethylene. In the present study, we determined the postharvest performance and ethylene sensitivity of cut flowers from 38 cultivated Hybrid Tea rose genotypes. The vase life of the cultivars varied considerably from 4.5 to 18.8 days at 21 °C. There was also substantial variation in the degree of flower opening among genotypes. Exposure to 1 μL·L−1 ethylene for 24 h at 21 °C reduced the longevity of 27 cultivars by 0.8 to 8.4 days (18% to 47%) by accelerating petal wilting and abscission. Ethylene treatment also significantly reduced rates of flower opening in 17 sensitive cultivars and in six cultivars that showed no ethylene-related reduction in vase life. Five cultivars showed no reduction in vase life or flower opening in response to ethylene exposure. Pre-treating stems with 0.2 mm silver thiosulfate liquid or 0.9 μL·L−1 1-methylcyclopropene (1-MCP) gas for 16 h at 2 °C reduced the deleterious effects of ethylene. The release of 1-MCP from two sachets containing EthylBloc™ into individual shipping boxes also protected flowers against ethylene applied immediately after a 6-d commercial shipment. The duration of protection afforded by the 1-MCP sachet treatment was greatest when flowers were maintained at low temperature.