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Martin P.N. Gent

experiments to examine the role of irradiance and temperature on the composition of lettuce ( Gent, 2014 , 2015 ). Here, we describe the effect of similar studies of composition in spinach grown in hydroponics in a greenhouse. We grew five plantings at

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John Erwin, Rene O’Connell, and Ken Altman

irradiance, photoperiod, and cool-temperature effects on flowering of the desert cactus hybrid Echinopsis ‘Rose Quartz’. ‘Rose Quartz’ is cross between Echinopsis silvestrii and another Echinopsis species (parent not reported, R. O’Connell) that is

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Robert M. Augé, Ann J.W. Stodola, and Brian D. Pennell

turgor loss point; Ψ p , turgor or pressure potential 1 Dept. of Ornamental Horticulture and Landscape Design. 2 Dept. of Plant and Soil Science. We gratefully acknowledge the assistance of David Coffey and Carl Sams in developing the irradiance

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Panpan Meng, Ying Ge, Qianjin Cao, Jie Chang, Peng Pan, Chi Liu, Yijun Lu, and Scott X. Chang

full sunlight among the irradiance levels (from 5% to 80% sunlight) studied. Lu and Xu (1988) and Zhang and Cao (2001) found that L. aurea had better cut flower quality when grown at 50% sunlight. Three other Lycoris species, L. chinensis

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Douglas A. Hopper, P. Allen Hammer, and James R. Wilson

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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John Erwin and Esther Gesick

; Chagvardieff et al., 1994 ; Dorais, 2003 ). The primary inputs into the photosynthetic process are light (irradiance), CO 2 , and water ( Björkman, 1981 ). Therefore, maximizing photosynthesis in leafy greens to maximize yield would require that irradiance, CO

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Amy L. Burton, Svoboda V. Pennisi, and Marc W. van Iersel

material, growers need production guidelines for irradiance, temperature, and nutrition regimes, as well as growth control. The majority of tropical foliage plants are produced for use indoors. Generally, photosynthetic photon flux ( PPF ) in postharvest

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Mark G. Lefsrud, Dean A. Kopsell, and Carl E. Sams

650 nm, respectively ( Koski et al., 1951 ). Environmental factors such as temperature and irradiance levels can have strong influences on the accumulation of plant pigments and glucosinolates ( Antonious et al., 1996 ; Charron and Sams, 2004

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Martin P.N. Gent

approximately half the reduction in irradiance. The response of the rate of fruit production to shade was delayed with respect to that for water or nutrient uptake. There was no response within 3 weeks after application of shade, a partial response in 3 to 6

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P. Lootens and J. Heursel

The short-term effects of photosynthetic photon flux (PPF), day/night temperatures and CO2 concentration on CO2 exchange were determined for two Phalaenopsis hybrids. At 20 °C, the saturating PPF for photosynthesis was 180 μmol·m-2s-1. At this PPF and ambient CO2 level (380 μL·L-1), a day/night temperature of 20/15 °C resulted in the largest daily CO2 uptake. Higher night temperatures probably increased the respiration rate and lowered daily CO2 uptake in comparison with 20/15 °C. An increase in the CO2 concentration from 380 to 950 μL·L-1 increased daily CO2 uptake by 82%.