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Trinidad Reyes, Terril A. Nell, and James E. Barrett

`Tara' and `Boaldi' were fertilized with 150 and 450 ppm from 20N–4.7P–16.6K soluble fertilizer and moved at flowering to postproduction conditions (21 ± 2C and 10 μmol·m–2·s–1). Shipping was simulated for 1 week at 26C. `Tara' exhibited burned leaf margins (necrosis) and chlorosis following shipping. At 150 ppm, leaves had brown, dried margins, but the damage did not progress indoors. Necrosis was worse at 450 ppm. Leaf chlorosis/necrosis of non-shipped plants at the 450 fertilizer level did not appear until the 3rd week indoors. At experiment termination, no leaf damage occurred in non-shipped `Tara' or `Boaldi' with 150 ppm. `Boaldi' did not show damage after shipping regardless of the treatment but symptoms (necrosis and wilting of leaves) evolved during the first 2 weeks indoors on plants fertilized with 450 ppm. A 50% reduction in root soluble carbohydrates was found at the highest fertilizer rate at flowering, suggesting that leaf chlorosis/necrosis is related to carbohydrate depletion in chrysanthemum.

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Brent M. Chapman, James E. Barrett, and Terril A. Nell

Catharanthus roseus `Cooler Peppermint' were grown under four different watering regimes [well-watered (WW), wilt plus 1 day (W+1), wilt plus 3 days (W+3), and wilt plus 1 day during the last 2 weeks only (L W+1)] and two different light levels [1100 and 750 μmol·m–2·s–1]. Stress treatments affected finished plant size and leaf area as well as stomatal conductance, water potential and time to wilt during two dry-down periods imposed at the end of an 8-week production cycle. W+3 plants were 50% smaller with 50% less leaf area compared to WW plants. During the second dry-down period, WW plants in high light wilted in 2 days vs 4 days for the W+3 plants. Similarly, WW plants in low light wilted in 3 days vs 6 days for the W+3 plants. The W+3 plants maintained significantly higher water potentials and greater stomatal conductances than the other treatments throughout both dry-down periods.

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Jeff B. Million, James E. Barrett, and Terril A. Nell

Drench applications of paclobutrazol (PBZ) are becoming increasingly popular as a means for controlling height in potted plants, and research is being conducted to quantify the distribution of PBZ following applications. In one trial, 120 ml of 0 or 1 mg 1-1 PBZ were applied to 15-cm pots filled with either Vergro Klay Mix (no bark) or Metro Mix 500 (bark). A bioassay using broccoli (Brassica oleracea L. Italica) seedlings was used to quantify PBZ in leachates and media following treatment drenches. Leachate PBZ concentrations were lower for Vergro than for Metro Mix 500; however, leachates for both media were <0.1 mg·liter–1. Concentrations of PBZ in media decreased with depth and were four to 10 times higher in the uppermost 2.5 cm than in lower horizons. For the uppermost 2.5 cm of media, higher PBZ concentrations were recovered in Metro Mix 500 than in Vergro. A follow-up study will compare surface vs. subsurface application methods on the movement of PBZ into pots.

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Robert H. Stamps, Terril A. Nell, and James E. Barrett

Leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] fronds produced under a high-temperature regime (HTR, 30 day/25C night) grew faster and produced sori earlier than those in a low-temperature regime (LTR, 20 day/15C night). Abaxial diffusive conductance was lower for HTR-grown fronds. Light-saturated net CO2 assimilation rates (Pn) and dark respiration were lower for HTR fronds, but light-saturated Pn efficiencies (chlorophyll basis); light compensation points; and soluble sugars, starch, and nonstructural carbohydrate levels were similar for the two regimes. Transpiration and water-use efficiency (mass basis) at light saturation were similar for fronds from both temperature treatments. Comparison of physiological characteristics of fronds from the two temperature regimes revealed no differences that might account for reduced postharvest longevity of fronds produced at the higher temperatures.

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

Treatments were cultivar, uniconazole concentrations (0, 2, 4, or 8ppm), and time between dip and placement under mist (0, 10, or 60 minutes). Unrooted chrysanthemum cuttings of cultivars `Tara' and `Boaldi' were dipped in uniconazole solutions for 10 seconds. Data were taken 16 days after treatment. A quadratic relationship was found for the interaction between concentration and cultivar. `Tara': (y = 6.7277-1.532(x) + 0.119409(x2)) and `Boaldi': (y= 6.4676-0.884(x)+0.060020(x 2). Time had no significant interaction with either cultivar or uniconazole concentration.

In a second study, with uniconazole concentrations and storage time (10 minutes or 12 hours), main effects and the cultivar concentration interaction were significant.

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William M. Womack, Terril A. Nell, and James E. Barrett

Dormant-budded `Prize' azaleas (Rhododendron sp.) were held at 2C, 7C, 13C, or 18C for 1, 2, 4, 6, 8, or 10 weeks then forced in walk-in growth chambers (29C day/24C night). Holding at 2C delayed flowering by 5-7 days over 7C and 13C. Plants held at 2C, 7C, or 13C for at least 4 weeks had approximately 50% buds showing color at marketability (8 open flowers). Plants held at 18C never exceeded 35% buds showing color at marketability. Increase in buds showing color was not apparent for plants were held at 7C, 13C, or 18C for more than 6 weeks; however, holding at 2C resulted in increasing percentages of buds showing color for holding periods longer than 6 weeks. Plants chilled at 13C and 18C showed significant increases in bud abortion after 8 or 10 weeks of cooling with most plants never reaching marketability (8 open flowers). These plants also had an increased proliferation of bypass shoots during cooling and forcing over other treatments.

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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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Thea M Edwards, Terril A. Nell, and James E. Barrett

Increased rates of senescence and ethylene related damage of potted flowering plants have been observed in supermarket produce areas where flowers and climacteric produce are displayed together. Ethylene levels in produce areas were found to average 20 ppb. An open system of clear glass chambers with fiberglass lids was designed to simulate retail supermarket conditions. The chambers were kept in postharvest rooms where light level and temperature could be controlled. In a 3 by 3 by 3 Box-Behnken design, Sunblaze `Candy' miniature potted roses were exposed to three levels of ethylene, 20, 40, and 80 ppb, for 1, 2, and 4 days. The three light levels used were: 0, 7, and 14 μmol·m-2·s-1. Ethylene damage was based on leaf and bud drop and decreased flower longevity.

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

Effects of photosynthetic photon flux (PPF) and temperature on quantitative axillary budbreak and elongation of pinched chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] plants were studied in three experiments. In Expt. 1, 12 commercial cultivars were compared under fall and spring environmental conditions. Spring increases in lateral shoot counts were attributable to increased PPF and air temperature. Cultivars varied from 0 to 12 lateral branches per pinched plant and by as much as 60% between seasons. There was a linear relationship between lateral branches >5 cm at 3 weeks after pinching and final branch count (y = 0.407 + 0.914(x), r 2 = 0.92). In Expt. 2, air was at 20 or 25C and the root zone was maintained at 5, 0, or –5C relative to air temperature. With air at 20C, lateral branch counts (3 weeks after pinch) declined by ≤50% with the medium at 15C relative to 25C. At 25C, lateral branch count was lower with medium at 30C than at 20C. Cultivars differed in their response to the treatments. Experiment 3 compared the interactions among temperature, PPF, and cultivar on lateral branch count. Depending on cultivar, the count increased the higher the PPF between 400 and 1400 μmol·m–2·s–1. Air temperature had no effect on lateral branch count. PPF had a stronger effect on lateral branch count than air temperature, and cultivars differed in their response.

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