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.
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.
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.
`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.
`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.
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.
`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.
The effect of two temperature regimes (29 °C day/24 °C night and 24 °C day/18 °C night) and of a 4-hour night interruption, during production, was studied on postproduction flower longevity and bud drop of 'Meirutral' and 'Meidanclar' potted, miniature roses (Rosa L. sp.). High production temperatures increased postproduction flower longevity and decreased postproduction bud drop. In 'Meidanclar', the high production temperature increased incidence of malformed flowers. No effects of night interruption could be shown on either postproduction flower longevity or bud drop.
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.
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.