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Twenty-six cultivars of chrysanthemum (Chrusanthemum morifolium Ramat.) of the standard, pot-, or spray- type were grown in greenhouses at an 8 hour short-day and a night temperature of either 15.S°C, or a split temperature of 15.5° from 1600 until 2400 and 10° from 2400 until 0800, The day temperature was kept at 22° on sunny and 18° on cloudy days. Additional light (about 3000 lx) was provided for one half of the plants in each temperature treatment on cloudy days. Good chrysanthemums were produced under all conditions with all cultivars with but a minor delay (about 3 days) at the split high-low night temperatures. The plants were taller when grown at the split cool rather than the normal night temperature. The number and size of flowers were not affected significantly by the temperature treatments. Additional light increased stem length and increased the number of flowers of the spray-, and pot-type chrysanthemums. In the growth and production of greenhouse-grown chrysanthemums the split, cool temperature treatments provide energy savings without a noticeable change in growth and quality of plants.

Open Access

This paper details the development and verification of ROSESIM, a computer simulation model of the growth of `Royalty' roses (Rosa hybrida L.) based on experimentally observed growth responses from pinch until flowering under 15 combinations of constant photosynthetic photon flux (PPF), day temperature (DT), and night temperature (NT). Selected according to a rotatable central composite design, these treatment combinations represent commercial greenhouse conditions during the winter and spring in the midwestern United States; each selected condition was maintained in an environmental growth chamber having 12-hour photoperiods. ROSESIM incorporates regression models of four flower development characteristics (days from pinch to visible bud, first color, sepal reflex, and flowering) that are full quadratic polynomials in PPF, DT, and NT. ROSESIM also incorporates mathematical models of nine plant growth characteristics (stem length and the following fresh and dry weights: stem, leaf, flower, and total) based on data recorded every 10 days and at flowering. At each design point, a cubic regression in time (days from pinch) estimated the plant growth characteristics on intermediate days; then difference equations were developed to predict the resulting daily growth increments as third-degree polynomial functions of days from pinch, PPF, DT, and NT. ROSESIM was verified by plotting against time each simulated plant growth characteristic and the associated experimental observations for the eight factorial design points defining the region of interest. Moreover, one-way analysis of variance procedures were applied to the differences between ROSESIM predictions and the corresponding observed means for all 15 treatment combinations. At 20 days from pinch, significant differences (P < 0.05) were observed for all nine plant growth characteristics. At 30 and 40 days from pinch, only flower fresh and dry weights yielded significant differences; at flowering, none of the 13 selected responses yielded significant differences. These graphical and statistical comparisons provide good evidence of ROSESIM's ability to predict the growth response of `Royalty' roses over a wide range of constant environmental conditions.

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Authors: and

Abstract

Growth and flowering of bleeding heart were promoted by 14 to 24 hour photoperiods or light interruptions in the middle of the night. Cold treatment of crowns promoted growth and flowering at short photoperiods. Light at 9 klx promoted growth and inflorescence formation, but greater intensities were required to achieve anthesis. Growing temperatures of 15-22.5°C were most desirable.

Open Access

Abstract

More rhizomes were initiated by plants of ‘Astrid’ chrysanthemum grown in short day and cool air temperature than in long day and warm air. Rhizome development was greatest, shoot growth was enhanced, and root length and dry weight increased with warm compared to cool soil temperature. Rhizomes grown at a cool soil temperature either in long or short days had the least cellular injury after exposure to –8°C.

Open Access

Abbreviations: A, leaf carbon assimilation; Ci, intercellular CO,; gs, stomata] conductance; LC, liter containers; TA, temperature at canopy height; TC, temperature at center location; TI, time of day; VO, container volume. Graduate research

Free access

( Zhang et al., 2015 ). However, extreme high-temperature events are becoming more frequent in south China as a result of increasing temperature and climatic variability, particularly during the flowering phenophase, thereby influencing cultivation ( Yang

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Abbreviations: DN, day-neutral; LT 50 , lethal temperature for SO% of flower buds; TNSC, total nonstructural carbohydrates. 1 Graduate student. 2 Research assistant. 3 Profcssor. We are grateful to the Agriculture Canada Research Station in Ste

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water and analyzed using high-performance liquid chromatography [HPLC (model L-6200; Hitachi, Tokyo, Japan)] with a polymer-based column [4.6 mm i.d. × 25 cm (Shodex ODP2 HP-4E; Showa Denko, Tokyo, Japan)]. The column temperature was set at 30 °C and the

Open Access

Abbreviations: ADT, average daily temperature; DIF, DT - NT; DIBE, days from pinching to day internode started to elongate; DT, day temperature; N, total number of internodes below inflorescence; NT, night temperature; VB, date of first visible bud

Free access

Abbreviations: ADT, average daily temperature; DIF, difference; DT/NT, day/night temperature; FR, far red; LD, long day; NI, night interruption; R, red; SD, short day. 1 Current address: Dept. of Horticultural Science, Univ. of Minnesota, 1970

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