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Adriano dos Santos, Francisco Eduardo Torres, Erina Vitório Rodrigues, Ariane de Andréa Pantaleão, Larissa Pereira Ribeiro Teodoro, Leonardo Lopes Bhering, and Paulo Eduardo Teodoro

end of plant breeding programs. Among them, the Toler method (1990), which uses a nonlinear regression model in the parameters, offers alternatives to overcome the difficulties related to the estimate of the environmental index. Furthermore, it

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Beth Ann A. Workmaster and Jiwan P. Palta

`Stevens' cranberry (Vaccinium macrocarpon Ait.) terminal bud freezing stress resistance was assessed by nonlinear regression utilizing relative scoring of the post-thaw bud growth and development based on defined bud stages 2 weeks following controlled freezing tests. Bud stages tested were chosen based on a phenology profile from each sampling date throughout the spring season. Previous year (overwintering) leaf freezing stress resistance was evaluated after both 2 days (injury) and 2 weeks (survival). The Gompertz function with a bootstrapping method was used to estimate the tissues' relative freezing stress resistance as the LT50. Bud injury levels (LT50) were expressed as the temperatures at which the mean potential regrowth capability was impaired by 50%, as compared with the unfrozen controls. In leaves, the LT50 is the temperature at which 50% injury (2-day evaluation) or survival (2-week evaluation) was modeled to occur. Dramatic changes in terminal bud relative freezing stress resistance occurred both within and between the tight and swollen bud stages. These results clearly show that seasonal changes in freezing stress resistance do not necessarily parallel changes in crop phenology and bud development. These results indicate that some physiological, biochemical, or fine anatomical changes may explain the seasonal loss in hardiness within a visual bud stage. Previous year leaves may possess the ability to recover from freeze-induced injury, as leaf survival was found to be the most reliable indicator of cranberry leaf hardiness. Major shifts in phenology and bud and leaf hardiness coincided with the rise of minimum canopy-level air temperatures to above freezing. The nonlinear regression technique utilized made it possible to estimate LT50 with data points comprising half or more of the sigmoidal dose response curve. Our study provides precise and quantitative estimates of the cold hardiness changes in cranberry terminal buds and leaves in spring. From precise estimates we were able to define critical temperatures for the impairment of cranberry bud growth. This is the first systematic study of cranberry terminal bud cold hardiness and spring bud development in relation to changes in the soil and air temperatures under natural conditions. Our study shows that regrowth assessment of the cranberry upright inherently describes the composite effects of freezing stress on plant health.

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Jacob H. Shreckhise, James S. Owen Jr., and Alex X. Niemiera

increase in SDW (i.e., grams SDW per mg·L −1 P applied) in hydrangea and azalea when compared with low (i.e., 0.5–1.0 mg·L −1 P) or high applied P concentrations (i.e., 4.0–6.0 mg·L −1 P; Fig. 3 ). Nonlinear regression was used to describe the pattern

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Robert D. Berghage and Royal D. Heins

Elongation characteristics of each internode on a lateral shoot of poinsettia (Euphorbia pulcherrima Klotz) `Annette Hegg Dark Red' were determined from pinching through anthesis for plants grown with 36 day/night temperature (DT/NT) combinations between 16 and 30C. The Richards function was used to describe the elongation of each internode. The first internode developing on a lateral shoot was longer and matured faster than subsequent internodes. The length of the first internode was a function of the difference between day and night temperatures (DIF = DT - NT). Subsequent internodes elongated uniformly in the absence of flower initiation. In the absence of flower initiation, the length of an internode, after the first, was a function of DIF. Internodes were shorter as proximity to the inflorescence increased. Internode length after the start of short days was a function of DIF and the visible bud index where visible bud index = [(days from pinching to the day an internode began to elongate - days from pinching to the day of the start of flower initiation)/the number of days from pinching to visible bud]. A poinsettia lateral shoot elongation model was developed based on the derived functions for internode elongation. The model predicted lateral shoot length within one standard deviation of the mean for plants grown in a separate validation study with 16 combinations of DT/NT. The model allows the prediction of lateral shoot length on any day from pinching through anthesis based on temperature, the number of nodes on the lateral shoot, the time each internode on the lateral shoot began elongating, and the visible bud index at the start of elongation of each node.

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Ada Baldi, Anna Lenzi, Marco Nannicini, Andrea Pardini, and Romano Tesi

despite a significant nonlinear regression ( Table 2 ). The number of secondary stolons increased along with N increase fitting a linear regression model, but only the difference between zero N and triple N was significant ( Table 2 ). Trenholm et al

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Maksut Barış Eminoğlu, Uğur Yegül, and Kamil Sacilik

content, and M o = initial moisture content. Because the relative humidity is continuously fluctuating within the dryer, M R was reduced to M / M 0 ( Diamente and Munro, 1993 ). A nonlinear regression procedure was used to calculate rate constants

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Luther C. Carson, Monica Ozores-Hampton, Kelly T. Morgan, and Jerry B. Sartain

-linear regression was calculated, and a Student’s t test was used to compare nonlinear regression coefficients between years for each CRF. Results and Discussion Weather conditions. The minimum, average, and maximum air temperatures from placement until last

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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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Hiroshi Iwanami, Shigeki Moriya, Nobuhiro Kotoda, Sae Takahashi, and Kazuyuki Abe

variable of mth fruit at l th days of storage under j th storage condition in i th cultivar, and e ijlm is the residual of the regression line. Measurements of TA were subjected to a nonlinear regression ( Fig. 1B ). The nonlinear regression model