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'.
Amanda M. Miller, Marc W. van Iersel, and Allan M. Armitage
Mark P. Kaczperski, Allan M. Armitage, and Pamela M. Lewis
Seed of Petunia × hybrida `Ultra White' were germinated in #406 plug trays at 2.5 C and at a light intensity of 100 μ mol s-1m-2 using a 24 or photoperiod. At germination, seedlings were grown under natural light conditions for 8 hrs (SD) or for 8 hrs with the photoperiod extended to 16 hrs (LD) using incandescent bulbs. At approximately the 6th leaf stage, seedlings were stored at 5 C in the dark or at 12 μ mol s-1m-2 and a 24 hr photoperiod for 0 to 21 days. After storage, plants were potted n 10 cm pots and grown to flowering in a greenhouse. Plants grown under SD to the 6th leaf stage with no cold treatment were shorter. flowered later and had more lateral branching than unstored LD plants. Storage at 5 C decreased time to flower of SD plants and increased branching of LD plants regardless of photoperiod during storage.
James M. Garner, Starla A. Jones, and Allan M. Armitage
Two studies were conducted to determine the influence of decapitation (pinch treatment) and photoperiod treatments on stem length, days from planting to harvest, and flowering stem yield in two delphinium cultivars. Plants of Delphinium ×belladonna Hort. ex Bergmans `Völkerfrieden' received a hard pinch (removal of apex and all stem and leaf tissue associated with leaves ≤10 cm), soft pinch (removal of apex and all stem and leaf tissue associated with leaves ≤4 cm), or no pinch. Plants of the D. elatum L. `Barbara' series were grown under either long- or short-day photoperiod, each treatment with or without receiving a soft-pinch. Time from planting to harvest was longer in pinched plants than in nonpinched plants of both cultivars regardless of photoperiod. Flowering stems were longer in hard- and soft-pinched plants of `Völkerfrieden' compared to nonpinched plants, and with `Barbara', stem length of pinched plants was either longer or similar to that of nonpinched plants regardless of photoperiod. At 30 days after the commencement of harvest, yield of flowering stems for hard-pinched plants of `Völkerfrieden' was higher than that for nonpinched plants, but yield from soft-pinched plants was similar to that for those not pinched. Stem yield for `Barbara' was higher for pinched plants under the long-day photoperiod, but under short days, yield from pinched plants was similar to that for those not pinched. Long days appear to increase yield and reduce production time in delphinium cultivars. Commercial benefits may be realized by growing nonpinched plants for earliness and pinched plants for longer stems and higher yield.
Allan M. Armitage, James Garner, and Jimmy S. Greer
Natalia K. Hamill, Allan M. Armitage, and Stephanie L. Anderson
As part of the New Floriculture Crop Program at the University of Georgia, a research project was initiated in Fall 2004 to determine the suitability of 12 taxa of woody shrubs for forcing in the greenhouse. In this study, the influence of cooling on greenhouse forcing of (Caryopteris × clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns' and Sambucus nigra `Black Lace') was evaluated. Dormant rooted liners were cooled for 0, 6, or 10 weeks at 1.7 °C to 4.4 °C. With 0 and 6 weeks cooling, Caryopteris never reached an acceptable finish stage. With 10 weeks cooling, plants finished in 7 weeks in the greenhouse. With 0 weeks cooling, Leycesteria was salable in 13 weeks. With 6 and 10 weeks cooling, plants finished in 7 and 8 weeks, respectively. With 0 weeks cooling, Sambucus never reached a salable stage. With 6 weeks cooling, plants were salable in 11 weeks; with 10 weeks cooling, plants finished in 6 weeks. The data suggest that cold is necessary to force Caryopteris and Sambucus in the greenhouse, and that 10 weeks of cold resulted in the shortest production time for both taxa. Data show that 6 weeks cooling of Leycesteria resulted in the shortest production time, but cooling is not necessary. This experiment was repeated in 2005–06 and will be compared to the 2004 findings. Additional experiments conducted in 2006 will also be discussed.
Allan M. Armitage, Natalia K. Hamill, and Stephanie L. Anderson
As part of the New Floriculture Crop Program at the University of Georgia, a research project was initiated in Fall 2004 to determine the suitability of woody shrubs for forcing in the greenhouse. This paper will provide an overview of the research, indicating plants that were determined to be suitable for greenhouse forcing and sales in the retail area and those that were discarded from the program. About 15 taxa were initially selected for the program based on habit, foliar qualities, and flowering (if present). All plants were subjected to 1.7 °C to 4.4 °C for 0, 6, or 10 weeks in a controlled temperature cooler. Based on growth and visual characteristics, Leptodermis oblonga, Indigofera pseudotinctoria `Rose Carpet', Forsythia × intermedia `Golden Peep', and Philadelphus coronaria `Manteau d'Hermaine' were discarded. Caryopteris × clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns', Sambucus nigra `Black Lace', Philadelphus coronaria `Variegata', and Physocarpus oblongifolius `Summer Wine' were investigated further. Data presented for Physocarpus suggested that cooling was not necessary for growth; however, 10 weeks of cooling resulted in the least time to finish in the greenhouse. Zero, 6, and 10 weeks cold resulted in 17, 10, and 7 weeks finish time, respectively. Additional work on Kolkwitzia, Buddleia, and Wegelia conducted in 2005 and future research will be discussed.
Allan M. Armitage, N. H. Hamill, and S. Anderson
Research to determine protocols for greenhouse forcing of woody shrubs was initiated as part of the New Crop Research program at the University of Georgia. About 15 woody taxa were initially selected for the program based on habit, foliar qualities and flowering (if present). All plants were subjected to 1.7–4.4 °C for 0, 6, or 10 weeks in a controlled temperature cooler. Based on growth and visual characteristics, Leptodermis oblonga, Indigofera pseudotinctoria `Rose Carpet', Forsythia ×intermedia `Golden Peep' and Philadelphus coronaria `Manteau d'Hermaine' was discarded. Caryopteris x clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns', Sambucus nigra`Black Lace', Philadelphus coronaria`Variegata' and Physocarpus oblongifolius `Summer Wine' were investigated further. Data presented for Physocarpus suggested that cooling was not necessary for growth; however, 10 weeks of cooling resulted in the least time to finish in the greenhouse. Ten, six, and zero weeks cold resulted in 17, 10, and 7 weeks finish time respectively. Additional work conducted in 2005 and future research will be discussed.
Raymond Kessler, Allan M. Armitage, and David S. Koranski
Plug flats of Begonia × semperflorens-cultorum Hort. `Pizzazz Red', Vodka', and `Viva' were provided 0, 50, 125, or 200 μmol·s-1·m-2 metal-halide supplemental irradiance in the greenhouse for 0, 2, 4, 6, or 8 weeks. Treatments were initiated when seedlings were in the first true leaf stage (2 weeks after sowing). Plug-grown begonias reached transplantable dry weight and leaf area after 4 weeks of 125 μmol·s-1·m-2 supplemental exposure, while those under O and 50 μmol·s-1·m-2 required 6 to 8 weeks. Fewest number of days to visible bud and anthesis and the fewest number of nodes for all cultivars occurred after 2 weeks of 125 μmol·s-1·m-2 supplemental exposure. The same conditions achieved the greatest final leaf area and plant height; however, final dry weight was unaffected. Additional supplemental irradiance and/or exposure time did not accelerate flowering or improve vegetative growth of finished plants.
Julie A. Plummer, T. Eddie Welsh, and Allan M. Armitage
Zantedeschia aethiopica (L.) K. Spreng. `Childsiana' is a dwarf white calla lily with potential for pot culture. Nine stages of flower development from macrobud to senescence were described and shelf life under a low-light postproduction environment was examined. Flowers at the macrobud stage opened in the postproduction environment. Plants with flowers at the macrobud stage (Stage 1) and plants with spathes fully opened but before pollen shed (Stage 5) had shelf lives of 26 and 11 days, respectively.
Brian P. Gibbons, Timothy J. Smalley, and Allan M. Armitage
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.