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  • Author or Editor: G.S. Howell x
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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
Authors: and

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

The reliability and convenience of 5 viability tests were evaluated. Growth and tissue browning were the most reliable tests, but they required considerable time and were qualitative. Triphenyl tetrazolium chloride (TTC) reduction and specific conductivity were satisfactory for grape, but TTC was not as reliable as specific conductivity for cherry and raspberry. Neither test proved satisfactory for strawberry.

A second exotherm always indicated living stems and the absence of a second exotherm accurately predicted stem death. Freezing curves for raspberry showed the stems to be 5 degrees hardier than the control growth tests indicated.

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

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

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

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

Winter injury to branches of highbush blueberries (Vaccinium australe Small cv. Jersey) resulted when mechanical harvester use caused lesions on the branches during the harvesting process. Of the dead wood collected during 2 years study, more than 99% had such a lesion. The amount of wood lost increased as the vibration rates of the harvester increased and at high rates loss of bearing surface reduced production the following season.

Open Access

Abstract

Early introduction of honey bees into caged ‘Jersey’ blueberries was associated with increased yields and fruit size and suggests that hives be introduced in plantations for pollination not later than 25% of full bloom.

Open Access