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

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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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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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Michelle H. Williams, Terril A. Nell, and James E. Barrett

It is generally accepted that ethylene production is centrally located in petal senescence, however, non-climacteric flowers senesce irrespective of the presence of ethylene. The regulation of flower senescence may well be linked to protein synthesis. Our objective was to develop a simple tool which can be used in breeding programmes and\or the market place to determine potential longevity of a flower. Here, SDS-PAGE protein profiles of both potted and cut chrysanthemum flowers were determined from flowering to senescence. Generally, only minor changes in both protein content and the proportion of the major polypeptides were observed in the potted flowers. However, polypeptides at 40, 45 and 65 kDa increased during flower senescence and are of particular interest because they could be linked to flower longevity. The apparent stability of the proteins may contribute to the long postharvest life of the potted chrysanthemum.

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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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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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Barbara C. Poole, Terril A. Nell, and James E. Barrett

Premature flower bud abscission imposes a serious limitation on longevity of potted Hibiscus in interiorscape situations, Ethylene is known to be one causative factor. Past research has suggested that carbohydrate depletion of buds may also be involved,

A series of experiments was conducted to examine the relationship between carbohydrate levels and ethylene sensitivity of flower buds under low irradiance levels. Two cultivars were used: `Pink Versicolor', which is very susceptible to bud abscission, and the more resistant `Vista', In the first experiment, plants were harvested twice weekly after placement in interiorscape rooms (8.5 μmol m-2 s-1 for 12 hrs per day; 26.5°C day/night) until all buds had abscissed. At each harvest, buds from four size groups were collected for analysis. In the second experiment, source/sink strength of buds was manipulated by selective daily removal of certain sized buds. Remaining buds were collected just prior to abscission for analysis. In two additional experiments, `Pink Versicolor' plants were treated with either silver thiosulfate or ethephon prior to placement in interiorscape rooms. Plants were harvested twice weekly and buds collected. For all experiments, bud dry wt, total soluble sugars and starch content were determined.

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G.H. Pemberton, Terril A. Nell, and James E. Barrett

Senescence of gladiolus flowers, like many geophytes, does not involve a climacteric burst of ethylene. Eleven gladiolus cultivars were screened and all were non-climacteric (NC) for both respiration and ethylene production. Average ethylene levels for individual flowers were 0.5 μl C2H4/kg per h or less. As in other NC flowers, protein synthesis may be linked to senescence. Our goal was to identify specific proteins that were involved in the senescence process that could be used as indicators of postharvest longevity. SDS-PAGE protein profiles of cut gladiolus flowers were determined from a tight bud stage to senescence. Both increases and decreases were observed in major polypeptides that may be connected to postharvest flower longevity. Total protein content of gladiolus flower petals decreased by ≈70% during the profile period. This could explain the relatively short postharvest life of 3 to 5 days for individual gladiolus flowers. Total protein profiles were probed with an ACC synthase antibody to establish the relationship of this enzyme in NC senescence.

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Richard K. Schoellhorn, James E. Barrett, and Terril A. Nell

`Improved Mefo' chrysanthemums were grown at 22C/18C and 34C/28C day/night temperature regimes to evaluate the failure of lateral bud development following pinching of this temperature sensitive cultivar. The number of viable buds on plants at the high temperatures was 40% of number at low temperature. Loss of bud viability was categorized as those buds that were: 1) absent, or 2) those in which growth was present, but inhibited. Inhibited buds were visible swellings surrounded by dense masses of secondary cell wall material. Anatomical studies were completed to verify the absence of lateral buds and determine what cellular changes imposed inhibition on those buds that did develop. A second group of experiments demonstrated that moving low-temperature plants to the high temperature caused production of viable buds to decline. Plants were moved from high temperatures to low, and reciprocally to high from low temperature. Anatomical sampling of apical meristems began at time of shift and at 1, 2, 4, and 8 days after temperature shift. High-temperature meristems possessed predominantly non-viable lateral buds, with few viable buds present.

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Nadia Roude, Terril A. Nell, and James E. Barrett

Plant height, flower diameter, days to flower, and longevity of `Iridon' chrysanthemums [Dendranthemum × grandiflorum (Ramat.) Kitamura] were not affected by various N and K concentrations (112, 225, 337, and 450 mg·liter-1) supplied during the last 5 weeks of production. However, increasing N concentration increased medium conductance, while varying K concentration had no effect on conductance. Visual grade of `Iridon' after 3 weeks in a simulated interior environment showed an interaction between concentrations of N and K. In a second study, growth and longevity of `Iridon' were affected by NH4: NO3 ratios. Plants receiving a 0:1.0 ratio flowered 4 days later than plants receiving a 0.5:0.5 ratio and were taller than plants fertilized with a 1.0:0 ratio. Longevity was greater in plants receiving a 0:1.0 ratio than in those receiving 0.5:0.5 or 0.75:0.25 ratios. Also, longevity was similar in plants receiving NH4: NO3 ratios of 0:1.0, 0.1:0.9, 0.2:0.8, and 0.3:0.7. Plants receiving 0:1.0 lasted 6 days longer than those receiving a 0.4:0.6 ratio.