Rooted stem cuttings of Ilex crenata Thunb. `Rotundifolia' were grown in a controlled-environment growth chamber. Root-zone temperatures were controlled with an electric system. Shoot carbon exchange and root respiration rates were determined in response to root-zone temperatures of 28, 32, 36, and 40C for 6 hour·day–1 for 7 days. Photosynthesis was decreased by root zones ≥ 32C, while root respiration increased with increasing root-zone temperature. Decreased photosynthetic rates were not due to increased stomatal resistance.
William J. Foster, Dewayne L. Ingram, and Terril A. Nell
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.
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.
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.
William M. Womack, James E. Barrett, and Terril A. Nell
`Prize' and `Gloria' azaleas were budded at 29C day/24C night without growth regulators. Dormant-budded plants were held at 2, 7, 13, or 18C for 0, 0.5, 1, 2, 4, 6, 8, or 10 weeks and then forced in walk-in growth chambers (29C day/24C night). A model was developed to describe the effect of cooling temperature and duration on days to marketability (eight open flowers) and percent of buds showing color. Holding at temperatures below 7C, increases days to marketability up to 7 days. Extended cooling (beyond 6 weeks) at temperatures <7C increases percent of buds showing color. Extended holding at temperatures >7C decreases buds in color due to development of bypass shoots during cooling and increased bud abortion. Plants not receiving a cool-treatment or cooled for <2 weeks do not flower uniformly. Furthermore, the percentage of plants reaching marketability dramatically decreases for plants held longer than 6 weeks at temperatures >7C. Both cultivars show similar trends, but `Gloria' has greater variability.
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.
Terril A. Nell, Ria T. Leonard, A.A. De Hertogh, and James E. Barrett
Potted Lilium Asiatic hybrids `Aristocrat', `Horizon', and `Polka' were evaluated following 3, 6, or 9 days of transport at 2, 7, or 13C. `Aristocrat' and `Horizon' withstood transport with little or no effect on floral bud opening. `Polka' was the most sensitive cultivar to transport, where bud opening decreased 33% when transported at 13C for 9 days. Most floral buds opened on `Aristocrat' (90% to 98%), while fewer buds opened on `Horizon' (37% to 56%) and `Polka' (52% to 90%). Individual flower longevity and diameters were largely unaffected by transport. Plant longevity was reduced 4 to 7 days when transported for 9 days at ≥7C or for >3 days at 13C. Plant longevity averaged 16 days for `Aristocrat' and `Polka' and 12 days for `Horizon'. `Aristocrat' and the Oriental potted hybrid lily `Star Gazer' were maintained at postproduction conditions of 18, 21, or 24C at 7 or 14 μmol·m–2·s–1 after being commercially transported for 4 days at 5 ± 2C. Postproduction conditions had no effect on floral bud opening of `Aristocrat' (98% to 99%), while bud opening of `Star Gazer' was reduced 17% at 24C compared to 18C. Plants lasted 4 and 9 days longer at 18C than at 21 or 24C, respectively. Foliar discoloration was greatest at 24C. Irradiance level had no effect on the variables evaluated.
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.
Trinidad Reyes, Terril A. Nell, Charles A. Conover, and James E. Barrett
Effects of three light intensities (564, 306 and 162 μmol m-2 s-1) and three fertilizer rates (220, 440 and 880 mg/15 cm pot, weekly) were evaluated on acclimatization potential of Chamaedorea elegans. Treatments were applied during four months under greenhouse conditions after which plants were placed indoors (20 μmol m-2 s-1, 21±2C and 50% RH) for two months. Light compensation point (LCP) was significantly reduced by decreasing light intensity and increasing fertilizer rates. Leaf and root fresh and dry weights increased with irradiance while shoots were not affected. Chlorophyll a levels were higher in plants grown under the lowest light intensity. Carbohydrate content is being analyzed and anatomical examination of leaves studied. Plant performance indoors will be discussed. These studies demonstrate that Chamaedorea, a monocot, acclimatizes similarly to dicots.
Trinidad Reyes, Terril A. Nell, James E. Barrett, and Charles A. Conover
The effect of irradiance and fertilizer level on the acclimatization of Chamaedorea elegans Mart. was studied. Chamaedorea elegans was grown for 4 months in 1.6-liter pots under 162, 306, or 564 μmol·m–2·s–1 and fertilized weekly with 20N–4.7P–16.6K soluble fertilizer at 220, 440, or 880 mg/pot. At the end of the production period, plants were moved to interior rooms and maintained for 2 months at 20 μmol·m–2·s–1 for 12 h daily at 21 ± 1C and a relative humidity of 50% ± 5%. At the end of the production phase, the light compensation point (LCP) and the concentration of nonstructural carbohydrates were lower, and chlorophyll concentration was higher the lower the irradiance level. Increasing fertilizer concentration decreased the number of fronds, LCP, and nonstructural carbohydrates. After 2 months in the interior environment, LCP and number of fronds of C. elegans did not differ among treatments. Chlorophyll concentration of plants grown under 564 μmol·m–2·s–1 had increased 61%, while starch in the stem had decreased 43% relative to the concentration found at the end of the production period. In C. elegans grown under 306 μmol·m–2·s–1, stem starch depletion was only 13% during the interior evaluation period. These results indicated that C. elegans grown under the highest irradiance level used reserved carbohydrates in the interior environment while adjusting to low light and producing new leaves. Chamaedorea elegans was best acclimatized at the intermediate irradiance and medium fertilizer concentration.