Paclobutrazol was applied as soil drench to potted petunia, and the treated plants were shorter than untreated ones. Three types of compost were then made from the treated and untreated plants: the shoots, the medium (including roots), and both shoots and medium. They were mixed with Vergro Klay Mix at the ratios of 0%, 5%, 10%, 20%, and 40% (v/v). In a factorial experiment, plugs of Begonia semperflorens cv. Gin were planted in the media with compost. Plants grown in media containing paclobutrazol residue were shorter and had less dry weight compared to those grown in media containing no paclobutrazol residue. Compost ratios at 5% and 40% reduced plant height to 65% and 42% and shoot dry weight to 55% and 20% of the control plants, respectively. These results indicate that residues from plants treated with paclobutrazol may carry over in soil of landscape beds and affect the growth of subsequent crops grown in that soil.
Ahmed A. Al-Badawy, James E. Barrett, and Terril A. Nell
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.
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.
Nadia Roude, Terril A. Nell, and James E. Barrett
Chrysanthemums `Bright Golden Anne' and `Iridon' [Dendranthemum ×grandiflorum (Ramat.) Kitamura] were grown with N concentrations of 1.3, 2.6, or 5.2 kg N/m' of water during the crop cycle from either Osmocote slow-release 14N-6.2P-11.6K or 12.4N4.4P-14.lK or Peters soluble 20N-4.4P-16.6K. Plants were moved to simulated interior rooms at flowering to evaluate effects of the treatments on longevity. `Bright Golden Anne' longevity was not affected by fertilizer source, but `Iridon' longevity was reduced when Peters soluble fertilizer was applied at 2.6 and 5.2 kg N/m3 of water, whereas N concentration did not affect longevity when the slow-release Osmocote fertilizer was used. In an additional study, `Tip', `Copper Hostess', and `Iridon' were grown in three soil media using 1.3, 2.6, or 5.2 kg N/m' of water using Peters soluble 20N-4.4P-16.6K fertilizer from time of planting until flowering. Longevity increased as N concentration decreased when chrysanthemums were grown in Metro Mix 350, whereas N concentration had no significant effect on chrysanthemums grown in Vergro Klay Mix or a peat-perlite-sand mix. `Tip' showed significant in. creases in longevity as N concentration decreased.
Barrett C. Wilson, Jeff L. Sibley, and James E. Altland
A study evaluating the effects of varying levels of chilling on foliar budbreak of linden (Tilia spp.) culivars was initiated in 1999 in Auburn, Ala. [lat. 32°36'N, long. 85°29'W, elevation 709 ft (216m), USDA Hardiness Zone 8a]. Littleleaf linden (T. cordata) `Greenspire' and `Fairview' required the most chilling to produce measurable budbreak and exhibited the lowest budbreak percentages. Silver linden (T. tomentosa) `Sterling' and american linden (T. americana) `Redmond' needed the fewest hours of chilling to produce budbreak and exhibited the highest budbreak percentages. `Sterling' was the top performer in foliar budbreak percentage and in subsequent growth. Although `Redmond' attained high budbreak numbers, its overall growth during the following growing season was inferior to that of `Sterling', `Greenspire' and `Fairview'. This information can contribute to the development of regional planting recommendations, which can aid in the selection of lindens suitable for the area in which they will be grown. Calculated r2 values indicated the models used provided a good fit to the data for all cultivars.
José A. Monteiro, Terril A. Nell, and James E. Barrett
Five cultivars of potted miniature roses (`Candy Sunblaze', `Lady Sunblaze', `Orange Sunblaze', `Red Sunblaze' and `Royal Sunblaze') were grown until stage 1 (bud showing color with sepals starting to unfold). At this stage one half of the plants were moved to interior conditions (12 μmol s-1 m-2 from cool white fluorescent lights for 12 hr daily and 21 ± 1C) and the other half were maintained in the greenhouse at recommended production conditions. Stage 1 bud respiration, flower respiration at flowering and at 2, 4, 6 and 8 days after flowering were assessed for plants in the greenhouse and under interior conditions. Also, flower interior longevity was assessed for all the cultivars and the correlations between flower longevity and flower respiration at the different stages were analyzed. At flowering and under interior conditions `Red Sunblaze' lasted the longest (23 days) followed by `Orange Sunblaze' (18 days), `Lady Sunblaze' and `Candy Sunblaze' (16 days), and `Royal Sunblaze' (13 days) and flower respiration was 2.08, 2.74, 3.91, 3.59 and 3.94 mg CO2 g-1 hr-1, respectively. In miniature rose, flower longevity was negatively correlated with flower respiration rate (P = 0.01).
James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell
Experiments with' White Christmas' and `Carolyn Wharton' caladiums (Caladium × hortulanum Birdsey), croton (Codiaeum variegatum), brassaia (Brassaia actinophylla Endl.), `Annette Hegg Dark Red' poinsettia (Euphorbia pulcherrima Wind.), and `Super Elfin Red' and `Show Stopper' impatiens [Impatiens wallerana (L.) Hook.f.] determined effectiveness of paclobutrazol in solid spike form as compared to media drench applications for height control. Paclobutrazol drenches and spikes were effective for all crops tested, with a similar concentration response for all, except that drenches had greater efficacy than spikes on caladium. A reduced effect was observed when spikes were placed on the medium surface of `Super Elfin Red' impatiens, while placement in the middle of the pot or around the side was equally effective. These results indicate that the spike formulation of paclobutrazol has potential to provide adequate size control for floriculture crops with the possible exception of rapidly developing crops, such as caladiums. Chemical name used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-) penten-3-ol (paclobutrazol).
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.
Ahmed A. Al-Badawy, James E. Barrett, and Terril A. Nell
To evaluate importance of paclobutrazol residues on surfaces, begonia (Begonia semperflorens) cv. Whisky and chrysanthemum (Dendranthema grandiflora) cv. Coral Davis plants were grown in flats sprayed with paclobutrazol at 0, 50, 100, 200 and 400 ppm.
For begonia, the plant heights at 2 and 4 weeks after treatments were decreased by 39 to 49% and by 55-69%, respectively. The overall change in height ranged from 2.1 to 4.9 cm compared to 15.3 cm for the control plants.
For chrysanthemum, a reduction in plant height was observed and the overall change in height ranged from 2.9 to 5.6 cm compared to 28.8 cm for the control plants.
Based on these results, there is a potential for paclobutrazol to affect non-target plants when subirrigation is used.
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.