Search Results

You are looking at 51 - 60 of 84 items for

  • Author or Editor: Royal D. Heins x
  • All content x
Clear All Modify Search
Free access

James E. Faust, Hiroshi Shimizu, and Royal D. Heins

Surface temperature of a soilless medium in white, gray, and black plug sheets was measured to determine the value of using plug sheets of different colors to control soil temperature during seed germination and young seedling growth. Plugs sheets were placed in a greenhouse set at 25°C. Soil surface temperatures were measured with fine-wire thermocouples inserted into the top 1 mm of the soil. A thermal image analyzer was used to determine the temperature variation across the plug flat. At night, soil temperature in all three colored flats was 3°C below air temperature because of evaporation and net longwave radiative losses to the greenhouse glass. Surface temperature of moist soil increased as solar radiation increased. Soil surface temperature in the white sheet was 6.3 and 10°C warmer than the air under solar radiation conditions of 350 and 700 W ·m-2 (about 700 and 1400 μmol·m-2·s-1), which was 3 and 2°C cooler than soil the black and gray plug sheets, respectively. These data indicate plug sheet color influences soil surface temperature, but not as much as solar radiation does. Preventing high solar radiation during the summer is more critical than plug sheet color.

Free access

James E. Faust, Sven Verlinden, and Royal D. Heins

Rapid reduction in temperature for two to three hours starting at sunrise reduces stem elongation compared to elongation of plants maintained under constant temperatures during the day. This experiment was designed to determine if syringing plants with water at sunrise would substitute for a reduction in air temperature or enhance the response to the drop in temperature. Easter lily (Lilium longiflorum Thumb.) plants were exposed to constant 20°C or to 20°C and then 16°C for a 3-hr period following sunrise. Half the plants in each temperature regime were syringed at 30-minute intervals with 20°C water for 3 hr starting 20 minutes before sunrise. Shoot-tip temperature during the three-hr pulse time averaged 20.0 and 17.3°C for the dry plants and 17.3 and 14.7°C for the syringed plants. Total elongation for the dry plants at 20°C was 30 cm and for the temperature-pulsed plants, 4.8 cm less; for the syringed plants, 3.3 and 5.8 cm less, respectively. While shoot-tip temperature of dry plants averaged 0.9°C above air temperature during the remaining hours of the day, syringed plants averaged 1.0°C cooler than the same air temperature even though plants had dried. The data indicate the reduction in stem elongation from a low-temperature pulse at sunrise can be enhanced by evaporative cooling.

Free access

Shi-Ying Wang, William H. Carlson, and Royal D. Heins

Argeranthemum frutescens `Butterfly' and `Sugar Baby', Brachycome hybrid `Ultra', Helichrysum bracteatum `Golden Beauty', Scaevola aemula `New Wonder',Supertunia axillaris hybrids `Kilkenny Bells' and `Pink Victory', Sutera cordata `Mauve Mist' and `Snowflake', and Verbena hybrid `Blue' were grown in a glass greenhouse maintained at 20°C under seven different photoperiods (10-, 12-, 13-, 14-, 16-, 24-hr, and 4-hr night interruption). Black cloth was pulled at 1700 and opened at 0800 HR; incandescent lamps provided 2 μmol·m–2·s–1 to extend light hours to the designed photoperiods. Seedlings were pinched 3 days after transplant. Responses to photoperiod were clearly species-dependent. The tested species can be classified into three groups: 1) stem elongation and flowering were promoted in the long-day treatment (A. frutescens and S. axillaris hybrids), 2) only stem elongation was promoted in the long-day treatment (S. aemula, H. bracteatum, and B. hybrid), and 3) neither flowering nor stem elongation were affected by photoperiod (S. cordata and V. hybrid).

Free access

Mark P. Kaczperski, Royal D. Heins, and William H. Carlson

Methods of cold storage for rooted cuttings of three cultivars of Pelargonium ×hortorum Bailey were examined. Cuttings were stored from 0 to 10°C for 7 to 56 days. Treatments included packing the cuttings in ice, storing them under irradiance levels of 0 or 50 μmol·m–2·s–1, applying fungicides, varying cutting developmental stages, and varying the day temperatures. Cuttings packed in ice showed signs of chilling injury within 7 days and died. Applications of etridiazole and thiophanate-methyl or metalaxyl and thiophanate-methyl drenches or fosetyl-Al spray did not improve storage performance of the cuttings. Roots of cuttings held 7 additional days in the propagation area before storage grew faster after storage than those of cuttings with less time in the propagation area, but flowering time was not affected. Maintaining night temperatures at 5°C while allowing day temperatures to rise to 10°C delayed flowering by 6 days compared to maintaining a constant 5°C. Rooted cuttings held at 5°C under 50 μmol·m–2·s–1 irradiance for 9 hours each day could be stored up to 56 days with only a 2-day delay in flowering compared to unstored cuttings. Chemicals used were 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole (etridiazole); thiophanate-methyl (dimethyl[1,2-phenylene)bis(iminocarbonothioyl)]bis[carbamate]) (thiophanate-methyl); N-(2,6-dimethylphenyl)-N-methoxyacetyl) alanine methyl ester (metalaxyl); aluminum tris (O-ethyl phosphonate) (fosetyl-Al).

Free access

Erik S. Runkle, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Thirty herbaceous perennial species were treated at 5°C for 0 or 15 weeks. Critical photoperiods for flower initiation and development with and without a cold treatment were determined. Photoperiods were 10, 12, 13, 14, 16, or 24 hours of continuous light or 9 hours plus a 4-hour night interruption. Continuous photo-periodic treatments consisted of 9-hour natural days extended with light from incandescent lamps. Species were categorized into nine response types based on the effects of cold and photoperiod on flowering. Plants had three flowering responses to cold treatment: obligate, facultative, or none. The perennials were obligate long-day, facultative long-day, or day-neutral plants. For example, Campanula carpatica `Blue Clips' had no response to cold and was an obligate long-day plant requiring photoperiods of 16 hours or longer or night interruption for flowering. Rudbeckia fulgida `Goldsturm' had a facultative response to cold and required photoperiods of 14 hours or longer or night interruption for flowering. Veronica longifolia `Sunny Border Blue' had an obligate cold requirement and was day-neutral. Some species responded differently to photoperiod before and after cold. Leucanthemum ×superbum `Snow Cap' flowered as an obligate long-day plant without cold and as a facultative long-day plant after cold. Response categories are discussed.

Free access

Grace M. Pietsch, William H. Carlson, Royal D. Heins, and James E. Faust

The effects of day and night temperatures (15 to 35C) and three irradiance levels [50% of ambient, ambient, and ambient plus 12 mol·m-2·day-1 of supplemental photosynthetic photon flux (PPF)] on development of Catharanthus roseus `Grape Cooler' were determined. Time to flower decreased by 30 days and leaf-pair unfolding rate (LUR) increased linearly as average daily temperature increased from 18 to 35C. Flower size was greatest when plants were grown at 25C. Supplemental light decreased days to flower and increased flower size. Flowering occurred when nine leaf pairs were present on the plant. Using the inverse of the LUR curve, i.e., days per leaf pair, the number of days to flower could be predicted at any time during plant development based on plant leaf number.

Free access

Beth E. Engle, Arthur C. Cameron, Royal D. Heins, and William H. Carlson

Storage of perennial plugs at subfreezing temperatures could be a valuable production tool since plants could be removed over relatively long periods for forcing. Several species of seed-propagated perennial plugs were pretreated at 0 and 5C under continuous 50 μmol·s-1m-2 PPF for 0, 2, 4, or 8 weeks. After each pretreatment period, plugs were placed into 4-mil polyethylene bags that were then sealed and placed at -2.5C for 0, 2, or 6 weeks. Plugs were then removed from the bags and placed into a 24C greenhouse for two weeks under ambient light levels and daylength, after which time they were rated for percent survival and general regrowth quality. Regrowth was not influenced by pretreatment temperature. Regrowth of Limonium dumosumtatarica, and Campanula carpatica `Blue Clips' following -2.5C storage was excellent with or without a pretreatment. Regrowth of Achillea filipendulina `Cloth of Gold,' Gaillardia grandiflora `Goblin,' and Iberis sempervirens `Snowflake' was improved on plugs given the 0 or 5C pretreatment. Hibiscus × hybrida `Disco Belle Mixed' regrowth was poor, regardless of pretreatment.

Free access

Mei Yuan, William H. Carlson, Royal D. Heins, and Arthur C. Cameron

Scheduling crops to flower on specific dates requires a knowledge of the relationship between temperature and time to flower. Our objective was to quantify the effect of temperature on time to flower and plant appearance of four herbaceous perennials. Field-grown, bare-root Coreopsis grandiflora (Hogg ex Sweet.) `Sunray', Gaillardia ×grandiflora (Van Houtte) `Goblin', and Rudbeckia fulgida (Ait.) `Goldsturm', and tissue culture—propagated Leucanthemum ×superbum (Bergman ex J. Ingram) `Snowcap' plants were exposed to 5 °C for 10 weeks and then grown in greenhouse sections set at 15, 18, 21, 24, or 27 °C under 4-hour night-interruption lighting until plants reached anthesis. Days to visible bud (VB), days to anthesis (FLW), and days from VB to FLW decreased as temperature increased. The rate of progress toward FLW increased linearly with temperature, and base temperatures and degree-days of each developmental stage were calculated. For Coreopsis, Leucanthemum, and Rudbeckia, flower size, flower-bud number, and plant height decreased as temperature increased from 15 to 26 °C.

Free access

Erik S. Runkle, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Six long-day species of herbaceous perennials were grown under six night-interruption (NI) photoperiod treatments to determine their relative effectiveness at inducing flowering. Photoperiods were 9-hour natural days with NI provided by incandescent lamps during the middle of the dark period for the following durations: 0.5, 1, 2, or 4 hours; 6 minutes on, 54 minutes off for 4 hours (10% or 6/54 cyclic lighting); or 6 minutes on, 24 minutes off for 4 hours (20% or 6/24 cyclic lighting). For five species, the experiment was repeated with more mature plants; for the sixth, Rudbeckia fulgida Ait. `Goldsturm', following a cold treatment of 8 weeks at 5 °C. The species generally showed a quantitative flowering response to the NI duration until a saturation duration was reached; as the length of the uninterrupted night break increased, flowering percentage, uniformity, and number and plant height increased and time to flower decreased. Minimum saturation durations of NI were 1 hour for Coreopsis grandiflora Hogg ex Sweet `Early Sunrise' and Hibiscus moscheutos L. `Disco Belle Mixed', 2 hours for Campanula carpatica Jacq. `Blue Clips' and Coreopsis verticillata L. `Moonbeam', and 4 hours for unchilled R. fulgida `Goldsturm'. Echinacea purpurea Moench `Bravado' flowered similarly across all lighting treatments. The 6/24 cyclic lighting regimen induced flowering comparable to that under a continual 4-hour NI for four of the six species and the cold-treated R. fulgida `Goldsturm'. Flowering under the 6/54 regimen was generally incomplete, nonuniform, and delayed compared to that under saturation duration treatments. Three of five species flowered earlier when more mature plants were placed under the NI treatments. Cold-treated R. fulgida `Goldsturm' flowered more rapidly than unchilled plants and the saturation duration of NI decreased to 1 hour.

Free access

Mei Yuan, William H. Carlson, Royal D. Heins, and Arthur C. Cameron

Most plants have a postgermination juvenile phase in which flower induction will not occur. Some species require a cold period for flower induction and will not respond to the cold treatments during the juvenile phase. We determined juvenile phases of Coreopsis grandiflora `Sunray', Gaillardia grandiflora `Goblin', Heuchera sanguinea `Bressingham', and Rudbeckia fulgida `Goldsturm'. Plants were exposed to 5C for 0, 10, or 15 weeks when Coreopsis had 0, 2, 4, 6, 8, or 10 leaves (>1 cm); Gallardia, 4, 8, 12, or 16 leaves; Heuchera, 8, 12, 16, or 20 leaves; Rudbeckia, 5, 10, 15, or 20 leaves. Plants were grown under a 4-h night interruption lighting (LD) or under a 9-h photoperiod (SD) after cold treatments. Based on time to flower and final leaf count, the juvenility of Coreopsis, Gaillardia, Heuchera, and Rudbeckia ended when they had about 6, 10, 12, and 15 leaves, respectively. Cold treatments were necessary for flower induction of Coreopsis and Heuchera and they increased the flowering percentage of Gaillardia and Rudbeckia. Heuhera was a day-neutral plant, Rudbeckia was on obligate LD plant, and Gaillardia and Coreopsis were quantitative LD plants.