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- Author or Editor: R. D. Heins x
- Journal of the American Society for Horticultural Science x
Abstract
In the paper, Influence of Photoperiod and Light Quality on Stolon Formation and Flowering of Chlorophytum comosum (Thunb.) Jacques by R. D. Heins and H. F. Wilkins (J. Amer. Soc. Hort. Sci. 103(5):687-689. 1978), the authors names were inadvertently omitted from the table of contents.
Abstract
Low irradiance levels, high temperatures, and water stress all promoted premature cyathia abscission in poinsettia ‘Annette Hegg Dark Red’ (Euphorbia pulcherrima Willd.). Abscission was greater in plants placed under 75% shade at 16°C night temperature (NT) than on plants placed under normal daylight (ND) at 16° or 21° NT. Water stress (0.6 MPa) promoted abscission on plants grown at an 18° NT and ND but did not promote abscission on plants grown at 16° NT and ND or on under 75% shade (13° to 21° NT). As plant density increased, transmission of photosynthetically active radiation (PAR) through the bracts to the leaf canopy decreased while cyathia abscission increased concomitantly. More than 90% of the PAR above the bracts was absorbed or reflected 5 cm below the bracts on 20 cm tall plants spaced at 65 or more plants m-2. Reducing natural irradiation 75% by shading leaves of poinsettia promoted cyathia abscission, whereas removing immature bracts decreased abscission. Leaf removal on plants with intact bracts promoted abscission to a degree that 100% of the cyathia abscised prior to anthesis, whereas bract removal on plants with intact leaves resulted in only 23% abscission of the cyathia 25 days after first anthesis. Measurements of nonsoluble carbohydrate showed a significant increase in leaf carbohydrate on plants with bracts removed while carbohydrate decreased in leaves of plants with bracts intact. Carbohydrate depletion appears to be the primary factor responsible for premature cyathia abscission in poinsettia.
Abstract
Chrysanthemum morifolium Ramat. ‘Bright Golden Anne’ plants were grown under 15 combinations of photosynthetic photon flux (PPF), day temperature, and night temperature in a central composite design. Time to flower was a function of both irradiance and the interaction between day and night temperature. The surface response to temperature was bowl shaped with delayed development as temperatures were either increased or decreased from the optimum combinations. High temperature delay was compensated for in part by increased PPF. Shoot length increased linearly as day temperature increased; final shoot length first decreased, then increased with increasing night temperature. The response surface appeared as a rising valley with the longest shoot lengths at high day temperatures. Total flower area per plant increased as PPF increased or as night temperature decreased. For any PPF and night temperature, maximum flower area occurred near 20°C. At a constant PPF, the response surface appeared as a rising ridge with maximum flower area at low night temperature.
Abstract
Plants of Chrysanthemum morifolium Ramat. cv. Bright Golden Anne irradiated as a day continuation or night interruption with light from cool white fluorescent tubes wrapped with red cellophane (red) produced more cuttings than plants irradiated with incandescent light. There were no significant differences in cutting production when plants were irradiated just prior to dawn. Increased cutting production from plants irradiated with red light was attributed to increased axillary bud activity, especially at the middle nodal position. When shoots were pruned to 4 or 8 nodes, the apical axillary bud produced the maximum number of cuttings and the basal produced the minimum, irrespective of light quality or time span of irradiation.
Abstract
Alstroemeria ‘Regina’ plants produced more vegetative shoots when the soil temperature alternated between 15°C (40 days) and 21° (20 days) as compared to a constant 15° soil temperature. However, a higher percentage of the shoots flowered from plants grown at the constant 15° soil temperature. Short days (8 hours light) inhibited flowering irrespective of soil temperature. Plants given a long-day treatment by exposing them to a night break with incandescent light flowered 6 weeks earlier than plants grown under normal day photoperiods during winter and spring and produced 30% more flowering stems. Treatments favoring flower development produced shorter flowering stems with fewer leaves. Maximum flower production resulted from plants grown at a constant 15° soil temperature and irradiated with incandescent lights as a night interruption.
Abstract
Irradiating the all-green Chlorophytum comosum Thunb. with incandescent or red cellophane wrapped fluorescent lamps during the night increased the mean number of stolons formed per plant. A night interruption was more effective in stimulating stolon formation than irradiating the plants prior to sunrise or at sunset. There were no significant differences in stolon numbers formed between the two light sources within an irradiation treatment. Less and less time was required between the advent of subsequent stolons under all treatments during the 25 week experiment. Photoperiod treatments had no effect on time from visible stolons to anthesis. Plants in all treatments formed stolons and flowered.
Stem elongation response to a single foliar application of the growth retardant chlormequat chloride [(2-chloroethyl) trimethylammonium chloride] for poinsettia (Euphorbia pulcherrima Klotz.) was quantified. Growth retardant applications did not affect final leaf count or timing of visible bud, first bract color, or anthesis. There was a statistically significant effect of growth retardant concentration on stem elongation, with a range from 289 ± 15 mm (mean 95% confidence intervals) for the control plants to 236 ± 17 mm at 4000 ppm. The growth-retarding effect during the first day after the application was not significantly different between 500 and 4000 ppm, and concentration primarily affected the duration of growth-retarding activity. A dose response function was incorporated into a three-phase mathematical function of stem elongation of single-stem poinsettia to predict elongation of treated and untreated plants. The model was calibrated using a data set from plants receiving 0, 500, 1000, 1500, 2000, 3000, and 4000 ppm, with a resulting R 2 of 0.99. Validation of the dose response model against an independent data set resulted in an r 2 of 0.99, and predicted final stem length was within 12 mm of observed final length.
Stem elongation of poinsettia (Euphorbia pulcherrima Klotz.) was quantified using an approach that explicitly modelled the three phases of a sigmoidal growth curve: 1) an initial lag phase characterized by an exponentially increasing stem length, 2) a phase in which elongation is nearly linear, and 3) a plateau phase in which elongation rate declines as stem length reaches an asymptotic maximum. For each growth phase, suitable mathematical functions were selected for smooth height and slope transitions between phases. The three growth phases were linked to developmental events, particularly flower initiation and the first observation of a visible flower bud. The model was fit to a data set of single-stemmed poinsettia grown with vegetative periods of 13, 26, or 54 days, resulting in excellent conformance (R 2 = 0.99). The model was validated against two independent data sets, and the elongation pattern was similar to that predicted by the model, particularly during the linear and plateau phases. The model was formulated to allow dynamic simulation or adaptation in a graphical control chart. Model parameters in the three-phase function have clear biological meaning. The function is particularly suited to situations in which identification of growth phases in relation to developmental and horticultural variables is an important objective. Further validation under a range of conditions is required before the model can be applied to horticultural situations.
Abstract
Long photoperiods (either naturally long days or 4-hour night interruptions with low intensity incandescent light) inhibited lateral shoot development and induced early flowering in perpetual flowering carnation (Dianthus caryophyllus). Short photoperiods delayed flowering but enhanced lateral shoot development only when shoots were vegetative. Once a shoot was induced, short photo periods had no influence on time to terminal shoot flower or on subtending vegetative lateral shoot development. Vegetative lateral shoot development was inhibited by night interruption lighting regardless of light source. These data indicate that high flower production in Spring and summer is due to lateral vegetative shoots which begin elongation and growth during the non-flower inductive short days of winter. At higher latitudes low production of flowers may not entirely be due to low photo-synthetic light but to the low number of lateral shoots. This low number of potential flowering shoots is due to highly inductive long days of summer which have caused shoots to flower before subtending lateral shoots can begin growth for future flower production.