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- Author or Editor: Allan Armitage x
The influence of temperature, irradiance, photoperiod and growth retardants on growth and flowering of Angelonia angustifolia Angel Mist series was evaluated. When temperature was increased from 15 to 30 °C, time to visible bud and time to flower decreased in a quadratic manner but total plant height and flower stem dry weight increased linearly. As irradiance increased, time to flower, time to visible bud, and height decreased quadratically. Changes in photoperiod had no effect on growth or flowering, suggesting that A. angustifolia is a day-neutral species with regards to height and flowering time. Daminozide, ancymidol, and paclobutrazol resulted in significant reduction of plant height compared with control plants but did not influence flowering time. Chemical names used: K-cyclopropyl-K-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); K-[(4-chlorophenyl)methyl]-K-(1,1-dimethyethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
The influence of cooling, photoperiod and chemical branching on early spring flowering of perennial species was studied. Cooling was provided while plants were in plugs (128 plugs per tray) and dikegulac-sodium, a compound found to induce breaks in other species, was applied prior to, during and after cooling. Plants were cooled in insulated lighted coolers for 4, 8 or 12 weeks at 4C, and brought to a greenhouse with night temperatures between 8-12C. Long and short days were provided in the greenhouse after plants came out of the coolers. Little response to dikegulac occurred, however, Campanula, Sedum, Leontopodium, Catananche, Aubrietia, Arabis, Gypsophila, Anchusa and Aquilegia responded to cooling and photoperiodic treatment. Flowering and vegetative characteristics such as internode elongation and plant height responded to photoperiod and cooling but not all genera responded similarly. Anchusa, Campanula, Aquilegia and Gypsophila flowered significantly earlier under LD compared to SD. Twelve weeks of cooling resulted in flowering of all genera, however, some genera were equally responsive to shorter cooling times.
The horticulture research gardens at the Univ. of Georgia were initiated in 1983, and have significantly evolved in visibility and functionality. The gardens were designed to act as a research evaluation site for the industry, but also to be used as a teaching tool for classroom, and to encourage student experience in landscape plant maintenance. Performance evaluation is accomplished by gathering data every 2 weeks, and performance plots are drawn for each taxon at the end of the season. Data on performance of perennial plants are also recorded, and each taxa is summarized after its flowering period. All data is compiled, simplified, and disseminated by booklet, trade magazine papers, and the Internet. In the last 7 years, a major cornerstone of the garden has become the evaluation and introduction of new crops for the ornamental plant industry. At least a dozen new taxa have been introduced. New crop introduction programs will be discussed as a potential means of funding. The ability to initially raise funds for horticultural trials the maintenance of funding over the years will also be discussed.
Plants of blue spirea (Caryopteris incana Mig.) were evaluated as cut flowers in the field and greenhouse. When subjected to several photoperiods but similar cumulative quanta, plants flowered more rapidly at 8 hours than at 12 hours and did not reach the macrobud stage at 16 hours. Stems were longer and their count was significantly higher with a 16-hour than an 8-hour photoperiod. In the field, yield and stem diameter were similar in full sun and in 55% shade. Stem length, however, significantly increased under shade.
In two studies, rooted cuttings of Phlox paniculata L. ‘Ice Cap’ (summer phlox) were cooled for 0, 4, 8, 12, or 16 weeks. Plants were forced in a glasshouse averaging 18 °C nights under extended-day and night-interruption lighting from incandescent lamps providing a minimum of 14 μmol·s−1·m−2 at plant level or continuous lighting from metal halide (HID) lamps providing a minimum of 400 μmol·s−1·m−2 at plant level. The influence of cooling duration on forcing days to flower, flowering stem counts, and flowering stem length was evaluated. Cooling plants promoted longer stems, higher flowering stem yields, and decreased days to flower when forced under long days provided by incandescent lamps, but when forced under HID lamps, days to flower for cooled plants were similar to those of noncooled plants regardless of cooling duration. Phlox forced in extended daylighting flowered in fewer days, had longer stems, and produced more flowering stems than those forced in night-interruption lighting. With continuous HID lighting, stem lengths and stems harvested per plant increased in a linear manner as cooling increased from zero to 16 weeks. Stem lengths ranged from 63.6 cm for noncooled plants to 96.3 cm for those receiving 16 weeks cooling, and flowering stem yields ranged from seven stems per plant for noncooled plants to 13 for those cooled 16 weeks. Phlox forced under HID lights flowered in substantially fewer days and had longer stems than those forced under incandescent lamps.
Light and temperature responses of whole-plant CO2 exchange were determined for two cultivars of Angelonia angustifolia Benth., `AngelMist Purple Stripe' and `AngelMist Deep Plum'. Whole crop net photosynthesis (Pnet) of `AngelMist Purple Stripe' and `AngelMist Deep Plum' were measured at eight temperatures, ranging from 17 to 42 °C. Pnet for both cultivars increased from 17 to ≈20 °C, and then decreased as temperature increased further. Optimal temperatures for Pnet of `AngelMist Purple Stripe' and `AngelMist Deep Plum' were 20.8 and 19.8 °C, respectively. There was no significant difference between the two cultivars, irrespective of temperature. The Q10 (the relative increase with a 10 °C increase in temperature) for Pnet of both cultivars decreased over the entire temperature range. Dark respiration (Rdark) of both cultivars showed a similar linear increase as temperature increased. As photosynthetic photon flux (PPF) increased from 0 to 600 μmol·m-2·s-1, Pnet of both cultivars increased. Light saturation was not yet reached at 600 μmol·m-2·s-1. The light compensation point occurred at 69 μmol·m-2·s-1 for `AngelMist Purple Stripe' and at 89 μmol·m-2·s-1 for `AngelMist Deep Plum'. The lower light saturation point of `AngelMist Purple Stripe' was the result of a higher quantum yield (0.037 mol·mol-1 for `AngelMist Purple Stripe' and 0.026 mol·mol-1 for `AngelMist Deep Plum'). The difference in quantum yield between the two cultivars may explain the faster growth habit of `AngelMist Purple Stripe'.
Five taxa of Helichrysum Mill. and Brachycome Cass. were recently evaluated for greenhouse production and amenity use. Preliminary studies on the influence of photoperiod, temperature, and growth regulators were conducted for H. bracteatum Vent., (syn Bracteantha bracteata) `Sunray' and `Matilda Yellow', H. apiculatum D.C, (syn Chrysocephalum apiculatum) `Golden Buttons' and Brachycome iberidifolia Benth. `Jumbo Mauve' and `Mauve Delight'. All taxa of Helichrysum were quantitative LD plants, flowering slightly more rapidly under night-break (2200-0200 HR) and extended day incandescent lighting, compared with 9-h short-day treatment. No influence of photoperiod occurred with cultivars of Brachycome. Constant temperature of 12, 20, or 28 °C were provided and all taxa demonstrated a linear decrease in flowering time as temperatures increased. The growth index (average of height and two measurements of width) was also influenced by temperature. Paclobutrazol and daminozide were applied at different concentrations and frequencies. Paclobutrazol was more effective than daminozide in both genera, and daminozide was ineffective in Brachycome.
Three biostmulants, Grow-plex (Menefee Mining Corp., Dallas, Texas), Roots 2 (LISA Product Corp., Independence, Mo.), and Root n' Shoot (Natural Organic Products International, Mount Dora, Fla.) were applied to transplanted plugs of Salvia splendens `Empire Red' and Begonia semperflorens-cultorum `Varsity Pink' and `Varsity Brite Scarlet'. Root n' Shoot drench (0.78%) solutions at transplant increased root weight, but a 1.56% solution decreased root weight of salvia; however, shoot growth was unaffected. Root n' Shoot decreased shoot growth of begonia, but did not affect root growth of begonia. Roots 2 treatments (0.25% or 2.00%) increased shoot weight of salvia, but did not affect salvia root growth or root or shoot growth of begonia. Spraying Grow-plex (0.78% or 1.56%) to runoff at transplanting and 2 weeks after transplanting did not affect root or shoot growth of salvia or begonia.
The effect of cooling method and duration on off-season cut flower production of Lysimachia clethroides Duby was examined. Rhizomes harvested in October were cooled for 0, 4, 6, 8, 10, or 12 weeks at 4 ± 1 °C in crates with unmilled sphagnum peat moss or in 3.75-L pots filled with a commercial soilless medium prior to forcing in a warm greenhouse. After 6 or more weeks of cooling, shoots emerged from crates in higher percentages than from pots. However, only the duration of cooling, not the method, affected the rate of shoot emergence, visible bud formation, and anthesis of the first bud in the raceme. As cooling increased from 0 to 12 weeks, the greenhouse days required for shoot emergence, visible bud formation, and anthesis decreased linearly. The number of flowering flushes and flowering stems produced per plant varied quadratically with cooling duration, and the highest yields occurred when rhizomes received between 4 and 10 weeks of cooling. High numbers of flowers were produced rapidly after 10 weeks of cooling. As the number of successive flowering flushes increased, the stem length increased linearly while the stem diameter decreased linearly.