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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.
The objective was to predict the distribution (mean and variance) of flower opening for an Easter lily (Lilium longiflorum Thunb.) population based on the variability in an earlier phenological stage and the expected average temperature from that state until flowering. The thermal time from the visible bud stage until anthesis was calculated using published data. `Nellie White' grade 8/9 Easter lilies were grown in five research and commercial greenhouse locations during 1995, 1996, and 1997 under a variety of temperature and bulb-cooling regimes. Distributions of visible bud and anthesis were normally distributed for a population growing in a greenhouse with spatially homogenous temperatures. The variance at anthesis was positively correlated with variance at visible bud. The mean and variance at visible bud could therefore be used to predict the distribution of the occurrence of anthesis in the crop. The relationship between bud elongation, harvest, and temperature was also incorporated into the model. After visible bud, flower bud length measurements from a random sample of plants could be used to predict the harvest distribution. A computer decision-support system was developed to package the model for grower use.
A model was developed to quantify the response of Easter lily (`Nellie White') flower bud elongation to average air temperature. Plants were grown in greenhouses set at 15, 18, 21, 24, or 27C after they had reached the visible bud stage. An exponential model fit the data with an R 2 of 0.996. The number of days until open flowering could be predicted using the model because buds consistently opened when they were 16 cm long. The model was validated against data sets of plants grown under constant and varying greenhouse temperatures at three locations, and it was more accurate and mathematically simpler than a previous bud elongation model. Bud length can be used by lily growers to predict the average temperature required to achieve a target flowering date, or the flowering date at a given average temperature. The model can be implemented in a computer decision-support system or in a tool termed a bud development meter.
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.
Abstract
Night irradiation of stock plants and cuttings during the rooting period with red (R) or incandescent (INC) light resulted in statistical differences in rooting of cuttings of chrysanthemum (Chrysanthemum morifolium Ramat. cvs. Bright Golden Anne and Mrs. Roy) but differences were not large enough to be of commercial concern. Rooting was best when stock plants were irradiated with R light and cuttings were subsquently rooted under INC light and poorest when cuttings from INC irradiated stock plants were rooted under R light.
Abstract
Plants of chrysanthemum (Dendranthema grandiflora Tzvelev.) were grown under one of 25 irradiance and temperature combinations from start of short days to flower. Four phases of development were defined as 1) the start of short days to the appearance of 4-mm terminal flower buds (phase I), 2) appearance of 4-mm terminal flower buds to removal of lateral flower buds when the terminal flower bud was 7 to 8 mm (phase II), 3) removal of lateral flower buds to flower buds showing first color (phase III), and 4) flower buds showing color to flowering (phase IV). Path analysis was used to study the influence of development time and relative dry weight gain during each of these four phases on development time and relative dry weight gain of subsequent phases. Relative dry matter accumulation during phases I, II, III, and IV significantly influenced cumulative relative dry weight gain, with phase I having the greatest influence. Increasing relative dry weight gain during phase I had a significant negative effect on relative dry weight gain in phase II. Time within each phase significantly affected total time to flower. Under the constant environmental conditions of this experiment, time in one phase did not influence the length of time in later phases.
Abstract
Chrysanthemum morifolium Ramat. ‘Bright Golden Anne’ cuttings were grown in a controlled environment at 50, 325, or 600 µmol·s–1·m–2 for 5 weeks at a 10-hr photoperiod. Photosynthetic rates were determined on individual leaves with an open gas analysis system at a range of photosynthetic photon flux (PPF) levels. Plants grown at low PPF (50 µmol·s–1·m–2) had a maximum net photosynthetic rate (Pn) that was about 39% of that for plants grown at 325 µmol·s–1·m–2. Pn of plants grown at 325 or 600 µmol·s–1·m–2 did not differ significantly.
Two fungicides registered for the control of Pythium spp. were evaluated for their effects on size and time to flowering of seed-propagated geraniums (Pelargonium × hortorum L.H. Bailey). Fungicide drenches of fenaminosulf and metalaxyl were applied to geraniums grown in soilless root medium: 1) at seeding (S); 2) at seeding and transplanting (ST); 3) at seeding, transplanting, and 1 week after transplanting (ST + 1); 4) at transplanting (T); and 5) 1 week after transplanting (T + 1). Metalaxyl drenching schedules did not significantly influence plant size or time to flowering. Fenaminosulf drenching schedules 3 and 4 significantly reduced plant size, and drenching schedule 3 significantly increased days to flowering in comparison to control plants. Although fenaminosulf is used infrequently because of limited availability, the detrimental effects of this fungicide on plant size and time to flowering warrant similar investigations with additional fungicides and crops. Chemical names used: sodium[4-(dimethylamino) phenyl]diazenesulfonate (fenaminosulf); N-(2,6-dimethylphenyl) -N-(methoxyacetyl) -dl-alanine methyl ester (metalaxyl).
Our objective was to quantify the stem-elongation patterns of several Oriental and Asi-florum lily cultivars to develop graphical tracking charts where actual crop height can be compared visually against a target growth curve. Oriental lilies (`Mona Lisa' and `Stargazer') were grown in research greenhouses at Michigan State Univ. (MSU) during 1994 and 1995. Asi-florum lily cultivars (`Centurion', `LA-87', `Non-stop', `Salmon Queen', and `Salzburg') were grown at MSU in 1995. Plants received constant 20 °C from emergence to flower in 1995, and constant 15, 18, 21, 24, or 27 °C in 1994. Elongation of Oriental lily plants followed a sigmoid pattern. Oriental lily cultivars elongated rapidly after emergence until 60% of the relative time between dates of emergence and first open flower, at which time plants had achieved ≈82% (`Stargazer') or 85% (`Mona Lisa') of their final height; elongation then exhibited a plateau phase. In contrast to the Oriental lilies, Asi-florum cultivars consistently exhibited a more constant elongation rate throughout the growing period. Simplified graphical tracking curves were developed based on the patterns of elongation and were programmed into a computer decision—support system (`UNH FloraTrack'). The graphical tracking curves were tested by growing `Stargazer', `Mona Lisa', and four Asiflorum cultivars (`Donau', `Dream', `Moneymaker', `Spirit') at the Univ. of New Hampshire and MSU during 1997 to height specifications of 51 to 56 cm (including a pot height of 15 cm). Sumagic growth retardants were applied as a prebulb dip at 5 ppm and as a foliar spray at 3 ppm when plant height was above the target curve. Final height targets were achieved using this method. E-mail prf@hopper.unh.edu; phone, (603) 862-4525.