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James E. Faust and Royal D. Heins

Leaf unfolding rate (LUR) was determined for `Utah' African violet plants grown in growth chambers under 20 combinations of temperature and photosynthetic photon flus (PPF). A nonlinear model was used to predict LUR as a function of shoot temperature and daily integrated PPF. The maximum predicted LUR was 0.27 leaves/day, which occurred at 25C and a daily integrated PPF of 10 mol/m2 per day. The optimum temperature for leaf unfolding decreased to 23C, and the maximum rate decreased to 0.18 leaves/day as the daily integrated PPF decreased from 10 to 1 mol/m2 per day. A greenhouse experiment using 12 combinations of air temperature and daily integrated PPF was conducted to validate the LUR model. Plant temperatures used in the model predicted leaf development more accurately than did air temperatures, but using average hourly temperature data was no more accurate than using average daily temperature data.

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Julie M. Tarara, Paul E. Blom, Bahman Shafii, William J. Price, and Mercy A. Olmstead

by variables measured rapidly and nondestructively in the field (e.g., Castelan-Estrada et al., 2002 ; Montero et al., 2000 ). Although canopy and fruit growth are nonlinear functions of time, they often are described using linear analyses (e

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Osamu Kawabata and Joseph DeFrank

A modified power function, y = (A + B·x)–C, was developed for determining the relationship between plant growth and growth retardant treatment. This function accounts for the plant response characteristics by incorporating three coefficients: A, growth level of the nontreated plants; B, the degree of growth reduction; and C, the smallest effective dose of the growth inhibitor. The function accounted for 97% of the variation in purple nutsedge (Cyperus rotundus L.) leaf length as a function of the amount of a growth retardant applied. The procedure resulted in a smaller error sum of squares than several common nonlinear functions because of its greater shape flexibility.

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Hans-Peter Kläring and Angela Schmidt

addition, Adams et al. (2001) derived a base temperature of 5.7 °C for fruit growth and development in tomato from measurements in a temperature range from 14 to 26 °C. They also used a nonlinear function to describe the effect of temperature on the time

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Giuseppe Colla, Carolina María Cardona Suárez, Mariateresa Cardarelli, and Youssef Rouphael

best described by nonlinear functions for all grafting combinations ( Fig. 1 ). All functions produced a coefficient of determination ( R 2 ) greater than 0.94 ( Table 1 ). No significant differences among grafting combinations were recorded on α values

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Jason Ernest Elvin Dampier, Richard W. Harper, Ashley McElhinney, and Eric Biltonen

assumed to grow at similar rates ( Del Tredici and Kitajima, 2004 ). Although tree growth curves typically follow nonlinear functions, a straight-line relationship was assumed for both diameter and height because of the relatively short time-series. Annual

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Eugene K. Blythe and Donald J. Merhaut

restrictions and assumptions such as similar particle size distribution of the components used in their study, which may not be typical in actual nursery practice. Milks et al. (1989) used a five-parameter, nonlinear function to predict physical property

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Mariateresa Cardarelli, Youssef Rouphael, Delia Muntean, and Giuseppe Colla

) , Colla et al. (2010 , 2011 ) ornamental cabbage cultivars showed that the SDW response curves to increasing nitrate availability were best described by a nonlinear function, where shoot biomass increased with the increase in nutrient-solution nitrate

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Geoffrey Weaver and Marc W. van Iersel

for developing crop-specific DPI or DLI recommendations. However, it is important to recognize that DPI is not a direct function of DLI, but rather of the integral of ETR over a day. ETR in turn is a nonlinear function of PPFD , and hence DPI not only

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Arthur Villordon, Christopher Clark, Don Ferrin, and Don LaBonte

results indicate that the variables used in this study failed to show nonlinearity, and various DM algorithms that fit nonlinear functions or interactions did not contribute to increased predictive accuracy. The partial residual plots ( Fig. 2 ) help to