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Renae E. Moran, Bryan J. Peterson, Gennaro Fazio, and John A. Cline

). When the trunk is damaged by cold temperature injury, every part of the tree is stressed by the reduced functioning of vascular tissues. This type of injury may increase in occurrence as winter and early spring temperature fluctuations occur more

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Mark E. Uchanski, Dawn M. VanLeeuwen, Steven J. Guldan, Constance L. Falk, Manoj Shukla, and Juliette Enfield

water temperature inside the barrel for the month of January. PAR was measured each season within 1 month of the winter solstice, 21 Dec., at noon. Measurements were taken at six locations associated with each high tunnel: outside the high tunnel

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Shengrui Yao

. ‘Perfection’ was the most vulnerable cultivar to winter damage and to late frost since it was the first to bloom among the six cultivars tested. With a lower early February minimum temperature, apricot at Los Lunas had fewer blooms than at Alcalde ( Fig. 3C

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Stephen S. Deschamps and Shinsuke Agehara

attain profitable winter strawberry yields in Florida ( Albregts and Chandler, 1993 ; Brooks, 1959 ). Beyond reducing daytime soil temperatures compared with black mulch, we also found that fully metalized mulch and metalized-striped mulch resulted in

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N. E. Pellett and D. Heleba

Five species of container-grown nursery plants were overwintered under treatments of no cover, 2 layers of microfoam, 15 or 30 cm of chopped newspaper and 15 cm newspaper or 22 cm straw between two layers of white copolymer. Temperatures were measured in the air under covers and in the center of the growing medium. Chopped newspaper moderated winter temperatures equal to or better than other cover treatments. All covers prevented winter injury. Baled chopped newspaper used by dairy farmers for livestock bedding is available at a reasonable cost.

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W.R. Okie and A.P. Nyczepir

Roots of dormant peach trees can grow when soil temperatures are >7 °C, which commonly occurs in the southeastern U.S. during the winter. In our tests, root growth on 1-year-old nursery trees was minimal at 7 °C, and increased with temperature up to at least 16 °C, but rootstocks varied greatly in their regeneration at a given temperature. Trees on seedling rootstocks of `Guardian™', `Halford' and `Lovell' regenerated roots more slowly than those on `Nemaguard' at soil temperatures >7 °C. The regeneration rates mirrored the relative susceptibility of these rootstocks to peach tree short life syndrome in the southeastern U.S., which is associated with parasitism by ring nematode.

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Fumiomi Takeda, Bernadine C. Strik, Derek Peacock, and John R. Clark

Transition to reproductive development and subsequent development of floral primordia (e.g., sepals, petals, stamens, and pistils) were determined in several blackberry (Rubus subgenus Rubus Watson) cultivars (Boysen, Cherokee, Chester Thornless, Marion, and Thornless Evergreen) growing in one or more locations (Clarksville, Ark., Aurora and Hillsboro, Ore., and Kearneysville, W. Va.). Also, daily maximum, mean, and minimum temperatures were recorded at three sites (Clarksville, Aurora, and Kearneysville) for the September to April sampling period. In buds of `Boysen' and `Marion' from Oregon, sepal primordia were first observed in November and December, respectively. Further floral bud development continued into January. Sepal development in `Cherokee' buds occurred in October in Oregon and in December in Arkansas. At all three sites, the buds of `Chester Thornless' blackberry remained undifferentiated until spring. The average mean temperatures in Oregon were generally well above 5 °C during the bud sampling period, but were near 0 °C on most days from mid-December to January in Arkansas and from December to late-February in West Virginia. The phenology of flower bud differentiation varied among the cultivars and was strongly influenced by prevailing winter temperatures. The results suggest that the shortening day lengths of late summer trigger flower bud development in blackberry. Floral bud development in blackberry, once initiated, was continuous; however, periods of low temperature (<2 °C) can arrest development.

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J.M. Caprio, H.A. Quamme, and R. Berard

89 POSTER SESSION 13 Temperature Stress/Cross-Commodity

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Rosa Marina Arvayo-Ortiz, Sergio Garza-Ortega, and Elhadi M. Yahia

Winter squash are grown in northwestern Mexico for export to distant markets. During transport, fruits deteriorate and develop fungal rots. Squash (Cucurbita maxima Duch. `Delica') was given hot-water dips at 50C for 0, 3, 6, 9, and 12 min and stored at 10 and 20C with 75% RH for 4, 8, and 12 weeks. The highest weight loss (11.3%) was in fruits without hot water treatment stored at 20C for 12 weeks—weight losses were 3.6%, 7.2%, and 10.2% in the 4-, 8-, and 12-week storage periods, respectively. At 10C, the weight losses were 3.4%, 6.8%, and 7.6% for the same periods, respectively. ß-carotene content increased from 36.2 to 54.2 mg/100 g after 4 and 8 weeks of storage, respectively, but declined to 42.8 mg/100 g after 12 weeks. Chlorophyll content decreased as temperature and storage period increased, changing from 16.7 to 10.8 mg·liter-1 at 10 and 20C and from 16.9 to 15.8 mg·liter-1 and 8.8 mg·liter-1 at 4, 8, and 12 weeks, respectively. Fruits had decay caused by Rhizopus and Aspergillus. Weight loss, ß-carotene and chlorophyll contents, and decay were not affected by length of hot-water treatment. General appearance was better in fruits stored at 10 than at 20C.

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Eric B. Bish, Daniel J. Cantliffe, and Craig K. Chandler

The demand for plug transplants by the Florida winter strawberry (Fragaria ×ananassa Duch.) industry may increase as water conservation during plant establishment becomes more important and the loss of methyl bromide fumigant makes the production of bare-root transplants more problematic. A study was conducted during the 1995-96 and 1996-97 seasons to determine the effect of container size and temperature conditioning on the plant growth and early season fruit yield of `Sweet Charlie' strawberry plants. Plants in containers of three sizes (75, 150, and 300 cm3) were grown in one of two temperature-controlled greenhouses (35 °C day/25 °C night or 25 °C day/15 °C night) for the 2 weeks just prior to transplanting into a fruiting field at Dover, Fla. Plants exposed to the 25/15 °C treatment had significantly higher average root dry weights at planting in 1995 and 1996 than did plants exposed to the 35/25 °C treatment. Plants exposed to the 25/15 °C treatment also had higher average fruit yields than the plants exposed to the 35/25 °C treatment (48% and 18% higher in 1995-96 and 1996-97, respectively). The effect of container size on plant growth and yield was variable. Plants propagated in the 150- and 300-cm3 containers tended to be larger (at planting) than the plants propagated in the 75-cm3 containers, but the larger container sizes did not result in consistently higher yields.