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Maude Lachapelle, Gaétan Bourgeois, Jennifer R. DeEll, Katrine A. Stewart, and Philippe Séguin

Chart. Weather data from a station located in that orchard were included in the CIPRA software. A base temperature of 5 °C, optimum temperatures between 22 and 25 °C, and a maximum temperature of 36 °C were used. The apple phenology model is divided into

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

rapidly. The GDD model can be incorporated into predictive models of sweetpotato crop phenology. To our knowledge, a well-defined phenological model does not exist for the species, and past reviews of sweetpotato yield physiology ( Kays, 1985 ; Ravi and

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J. Ryan Stewart, William R. Graves, and Reid D. Landes

Carolina buckthorn [Rhamnus caroliniana Walt. or Frangula caroliniana (Walt.) Gray] is an attractive and water-stress-resistant shrub or small tree distributed extensively in the southeastern United States that merits use in managed landscapes. Due to substantial climatic differences within its distribution (30-year normal midwinter minima range from 13 to -8 °C), selection among provenances based on differences in cold hardiness is warranted. Before selections are marketed, the potential of carolina buckthorn to be invasive also merits investigation. Ecological problems resulting from the introduction of Rhamnus L. species in the United States, most notably the dominance of R. cathartica L. (common buckthorn) over neighboring taxa, are due in part to early budbreak. Consequently, we investigated depth of cold hardiness and vernal budbreak of carolina buckthorn and common buckthorn. Stem samples of carolina buckthorn and common buckthorn collected in midwinter survived temperatures as low as -21 and -24 °C, respectively. Although the cold hardiness of carolina buckthorns from Missouri was greater than that of carolina buckthorns from Ohio and Texas on 2 Apr. 2003, there were no differences in cold hardiness of stems from Missouri and Texas on all three assessment dates in the second experiment. All plants survived at both field locations except for the carolina buckthorns from southern Texas planted in Iowa, which showed 0% and 17% survival in 2003 and 2004, respectively. Budbreak of both species with and without mulch in Ames, Iowa, was recorded from 9 Apr. to 10 May 2002. Mean budbreak of common buckthorn was 5.7 days earlier than budbreak of carolina buckthorn, and buds of mulched carolina buckthorns broke 4.2 days earlier than did buds of unmulched carolina buckthorns. We conclude that the cold hardiness of carolina buckthorn is sufficient to permit the species to be planted outside of its natural distribution. Populations of carolina buckthorn in Ohio and Missouri should be the focus of efforts to select genotypes for use in regions with harsh winters. Phenology of its budbreak suggests carolina buckthorn will not be as invasive as common buckthorn, but evaluation of additional determinants of invasiveness is warranted.

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Anita Solar and Franci Štampar

per year. The orchard was not irrigated, and was modestly fertilized with nitrogen, potassium, and phosphorous. Data were collected on each individual plant starting in 1999. Traits relating to phenology, yield, nuts, kernels, and health status were

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Thomas E. Marler and Nirmala Dongol

cycad species that are represented by only a few individuals. All cycads are dioecious, so a grower that does not have access to cryostorage facilities must enable synchrony of reproductive phenology among individuals to realize success ( Marler, 2010

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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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Krista C. Shellie

.E. 1990 Yield and enological characteristics of grape cultivars in central Washington 1974–1987 Ext. Bul. 1591, Washington State Univ Pullman The Northwest Berry and Grape Information Network 2004 Online phenology and degree-day models for agricultural

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Richard A. Criley and Setapong Lekawatana

Although in florescences of H. chartacea `Sexy Pink' can be harvested year'round in Hawaii, flowering is heaviest during the summer while demand is higher during winter months. The research was directed at identifying influences affecting the timing and rate of flower development, Dissection of apices of pseudostems which began development during June-July showed reproductive development (3-6 cm) in Jan-Feb when @6 leaves had unfurled. Some pseudostems had aborted the growing point after initiation had occurred. Data from 141 flowering pseudostems over 2 years of sampling showed that approx. 46 weeks were required from shoot emergence to flowering. Seasonal variation existed for leaf number and developmental period. The paper will analyze the influence of temperature on these two components of flowering.

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Peter Allan, Alan George, and Robert Nissen

Low chill `Flordaprince' peach trees were grown in subtropical Australia, either following paclobutrazol application to dwarf the trees, or extra nitrogen to invigorate them. Fruits were thinned uniformly. Paclobutrazol significantly reduced the competing spring shoot growth and gave earlier maturity of larger, better quality fruits. It reduced the spring, but increased the autumn root flush. Stage 2 of fruit growth was slightly longer in vigorous trees, resulting in delayed seed growth and greater dry mass of the embryos. Starch reserves were greatest in the roots, followed by the trunk, shoots and leaves. The reserves were lowest during the second half of fruit development, but rose again after the end of shoot extension growth. Leaf N, P, and K levels decreased through the season while Ca and Mg increased. There were significantly lower K and higher Ca and Mg levels in dwarfed trees.

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Lauren C. Garner and Carol J. Lovatt

excessive. Clearly, a strategy to reduce the abscission of reproductive structures would increase avocado yield. The reproductive phenology of many avocado cultivars, including ‘Hass’, is further characterized by alternate bearing. Alternate bearing is a