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Biweekly cold hardiness and water content were measured on 1-year-old field cuttings of bearing Concord grapevines at the Horticultural Teaching and Research Center at MSU from Sept. 1998 to Apr. 1999. Cold hardiness index LT50 (temperature at which 50% of the sample was killed) was determined by three viability tests after laboratory controlled sub-freezing treatments. Weather data were obtained from the MSU agricultural weather automatic system. Average maximum and minimum air temperatures of 1, 3, 5, and 7 days prior to each field sampling were regressed against the LT50 of the tissues. Our results suggested that: 1) Tmin1 (minimum air temperature of the preceding 1 day of each sampling) had the most significant correlation with LT50 and cane water content among all air temperatures analyzed. 2) While cane water content was significantly related to its bark water, the water content of periderm and pith did not. 3) When comparing the effects of Tmin1 and bark water content on cane LT50 together, bark water had significant higher coefficient of determination (R 2). This research provided additional information about the mechanisms of plant dormancy and cold hardiness.

Free access

Abstract

Field death of dormant primary buds of Vitis labrusca L. cv. Concord may be effectively simulated by in situ puncture with an aluminum needle super-cooled by liquid N2. This allows the subsequent development of the secondary buds for studies of their growth and productivity.

Open Access

Mature vigorous `Concord' grapevines (Vitus labruscana, `Bailey) at Clarksville, MI, were excavated at two to five week intervals from 29 April (bud break) until 28 September. Vines were separated into roots, wood (trunks and cordons), new shoots and leaves, and fruit. Tissues were weighed, then analyzed for total N to determine how much N vines accumulated annually, and when absorption occurred. Vines contained 18 g N at bud break, 75 g at fruit maturity, and 43 g when leaves were becoming senescent in late September. At fruit maturity when vine N content was highest, the new shoots and leaves, fruit, roots, and wood contained 53, 28, 11 and 8% of vine N, respectively. Vines absorbed N most rapidly between late May and early July, when the most rapid vegetative growth occurred.

Free access

Abstract

The acclimation and deacclimation rates of wood and flower buds of tart cherry were determined over 2 seasons and related to the time of defoliation that occurred as the result of pathogenic infection or hand removal during the first year of study. Early leaf loss resulted in delayed acclimation in the fall and more rapid deacclimation in the spring. The end result was reduced bud survival and decreased fruit set. The effects of early defoliation carried over into the second year.

Open Access

Abstract

Horticulturalists frequently use the analysis of variance (F-test) to determine treatment differences. Many simple non-parametric tests, which require fewer assumptions, are also available. This note presents an example of the modified Friedman test as an alternative analysis for ranked data from a randomized complete-block design.

Open Access

Abstract

Environmental and phenological factors considered potential components of flower bud hardiness of highbush blueberry (Vaccinium australe Small) were regressed against hardiness (T50). Three multiple regression equations were derived from 1 year’s hardiness and component data on 7 commercial highbush cultivars. Factors considered in the models were air temperature, photoperiod, bud dry weight, bud moisture content, bark color, date of leaf drop and pollen tetrad formation in the field and time to 50% flowering. The standard deviations of the estimated T50 values from the actual T50’s were 1°C or less.

Open Access

Abstract

Cold resistance of primary buds from grapevines (Vitis spp.) decreased with advancing phenological development. Morphological characteristics of canes produced during previous growing season had no effect on bud hardiness at a given stage of development or on development rate when cuttings were forced in the greenhouse. Cultivar differences were found to affect both the rate of bud development and the hardiness at a given stage of buds forced from stored cuttings.

Open Access

Abstract

It has been necessary for perennial plants to develop systems for sensing and reacting to environmental parameters. Their survival and perpetuation is determined, in large measure, by the timing of vital processes in relation to favorable and unfavorable cycles of environment. While the regulation of flowering by environmental stimuli has been extensively researched little is known about the control of cold acclimation. Recent studies show striking similarities between the control mechanisms for flowering and cold acclimation in temperate zone plants.

Open Access

Abstract

Flower bud hardiness of seven commercial highbush blueberry cultivars (Vaccinium australe Small) was determined from fall to spring for two consecutive years. Hardiness was expressed as T50, estimated by Spearman-Kärber equations. The T50 values for cultivars showed good agreement with spring field survival. Distal buds were less hardy than proximal buds on the same twig. The Average Exotherm (AET) methods were more variable than the T50 method for determining flower bud hardiness.

Open Access
Authors: and

Abstract

The relationship of environmental temperature to the cold resistance of apple bark tissue was studied on mature orchard trees in the field during natural spring dehardening and on 3 and 4 year old trees in the containers which were dehardened under controlled conditions. Field studies showed day to day fluctuations in dehardening and rehardening during the spring in each of 2 years. These short term changes in cold resistance were closely related to the air temperatures of the preceding day. In controlled studies, hardy plants during the winter dehardened as much as 15°C in one day in a warm greenhouse, and rehardened 15° in 3 days when they were held at −15°. The dehardening process was only partially reversible. Once dehardening began, the bark did not reharden beyond a certain base level. This base level raised with each successive day of dehardening. The base level usually corresponded to the minimum killing temperature on the day preceding the final day of dehardening.

Open Access