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Fan-Hsuan Yang, David R. Bryla, and Bernadine C. Strik

collected at green and blue stages of development were separated using Tukey’s honestly significant difference test (α = 0.05). Means of sun-exposed and shaded berries were compared by paired t test (α = 0.05). Critical temperature and heating times for

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M.J. Willett, E.L. Proebsting, and R.E. Redman III

Flower buds of peach, apricot, and sweet cherry are killed by low temperatures during winter and spring. Frost protection measures used commonly in the spring are applied to freeze protection during the winter in the Yakima Valley of Washington. Critical temperatures change rapidly during winter. To succeed, winter freeze protection requires adequate inversions, equipment that operates at temperatures below -15C, and reliable estimates of critical temperatures for flower bud survival. Observations and experience have shown that inversions develop on most critical winter nights. Wind machines and orchard heaters will operate under severe low-temperamre conditions. Winter freeze protection has been practiced successfully on an increasing scale in the Yakima Valley for more than 20 years. Five packinghouses operate laboratories to measure critical temperatures. A computer model that estimates critical temperatures from daily or hourly air temperatures is being incorporated into these estimates.

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Carlos Miranda, Luis G. Santesteban, and José B. Royo

The influence of the species in spring frost sensibility was determined for the Prunus species peach (P. persica (L.) Batsch), sweet cherry (P. avium L.), almond (P. dulcis (Mill.) Webb/P. amygdalus Batsch), japanese plum (P. salicina Lindl.), and blackthorn (P. spinosa L.). The confidence intervals for lethal temperatures of 10% (LT10) and 90% (LT90) bud injury were also determined. In 2000 and 2001, seven frost treatments were made for each one of the phenological stages comprised between B (first swell) and I (jacket split) in two cultivars per each species. The relationships between frost temperature and the proportion of frost damaged buds for each cultivar, year, and phenological stage were adjusted to linear regression models. The 95% confidence intervals were also calculated. The spring frost hardiness order of the species, from the least to most hardy, was as follows: sweet cherry, almond, peach, japanese plum, and blackthorn. Despite the highly homogeneous nature of the frost and bud characteristics, the temperature range for a given injury degree was quite broad, since the confidence interval's breadth for LT10 was as high as about 3 °C and as high as about 6 °C for LT90. Consequently, when critical temperatures are used in making decisions as to when to begin active frost protection, a prudent measure would be to take the temperature references from the upper limits in the confidence intervals.

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Arthur T. DeGaetano

parameters ( Semenov et al., 1998 ). This was particularly true for minimum temperature variance which shows a considerable within-month change particularly during the spring when the phenological stage and critical temperature thresholds also change rapidly

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Michael J. Willett, Preston K. Andrews, and Edward L. Proebsting Jr.

There has been an explosion of interest in the development of computer-based Decision Support Systems (DSS) in agriculture. Humans factor, which is the design and evaluation of a system to optimize human and total system performance, offer tools to improve the usefulness of DSS. Task analysis, a formal human factors approach to study human-machine interaction, identifies all of the physical and psychological tasks which must be completed by either the human or the machine in order to meet the various system performance requirements and constraints. Our study focuses on the tasks associated with mid-winter stone fruit freeze protection. Using this technique we have identified work load and output requirements of current critical temperature estimation procedures, additional information needed to improve critical temperature estimates and training needs of fruit industry personnel making critical temperature determinations. This information will be used to produce a requirements specification for a freeze protection DSS.

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Qin Yang, Er Liu, Yan Fu, Fuqiang Yuan, Tingting Zhang, and Shu Peng

observation section, with three replications. To determine the critical temperature and duration of tolerance, branches containing inflorescences were cultured in a controlled climate chamber at 0, 5, 10, 15, 20, 25, 30, or 35 °C as described in the previous

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Ben Hong Wu, Hai Qiang Huang, Pei Ge Fan, Shao Hua Li, and Guo Jie Liu

). Pn seemed to increase with Tl until Tl reached a critical level. Above the critical temperature, Pn generally tended to decrease. The critical leaf temperature could be roughly indicated as 37 °C for ‘Qingfeng’, 39 °C ‘Okubo’, 38 °C for ‘Yanhong’, 35

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Frank B. Matta and Amin Kawatin

Stem critical temperatures for September showed that `Hughes' was later in acclimating than `Jackson'. Maximum hardiness for all cultivars occurred in January and deacclimation in February. Bud critical temperatures for September and October also showed that `Hughes' acclimated later than the other cultivars. Maximum hardiness for buds occurred in January and deacclimation in March. In December, the LT50 for the tetrazolium test, the electrolyte leakage test, and the tissue browning test were –18, –20, and –20C, respectively, as shown by differential thermal analysis of `Desirable'.

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Skyler Simnitt, Tatiana Borisova, Dario Chavez, and Mercy Olmstead

that this method of protection frequently provides lackluster results depending on the severity of the minimum temperature and the critical temperature at which damage occurs to the buds. As one of study participants explained regarding irrigation, A

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Darrell Sparks

Freezing and damaging temperatures were imposed on `Desirable' pecan [Carya illinoinensis (Wangenh) K. Koch] trees before budbreak and again during the beginning of pistillate anthesis. Freezing temperatures imposed before budbreak resulted in abnormal flowering; freezing temperatures during anthesis did not. Abnormal flowering depends on both a critical temperature (about -1.7 to -2.2C) and a critical stage of pistillate flower bud development within the 8- to 10-day interval before budbreak.