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  • Author or Editor: H. Jiang x
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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.

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We investigated the FT/TFL1 family of peach (Prunus persica), a gene family that regulates floral induction in annual and perennial plants. The peach terminal flower 1 gene (PpTFL1) was expressed in a developmental and tissue-specific pattern that, overall, was similar to that of TFL1 orthologs in other woody Rosaceae species. Consistent with a role as a floral inhibitor, ectopic expression of PpTFL1 in arabidopsis (Arabidopsis thaliana) delayed flowering and prolonged vegetative growth. Other members of the peach FT/TFL1 family were identified from the sequenced genome, including orthologs of flowering locus T, centroradialis, brother of ft, and mother of ft and tfl. Sequence analysis found that peach FT/TFL1 family members were more similar to orthologous genes across the Rosaceae than to each other. Together these results suggest that information on genes that regulate flowering in peach could be applied to other Rosaceae species, particularly ornamentals.

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Seasonal alteration of the cytosolic and nuclear Ca2+ concentrations of spruce (Picea engelmannii Parry) and brome grass (Bromus inermis Leyss) was investigated by the antimonate precipitation cytochemical technique. Electron microscopic (EM) observations revealed that electron-dense Ca2+ antimonate deposits, an indication of Ca2+ localization, were seen mainly in the vacuole, the cell wall and the intercellular space in samples of both species, collected on 14 July 1997. Few deposits were found in the cytosol and nuclei, showing a low resting level during summer months. On 8 Aug. 1997 following a decrease in daylength of 1 hour and 12 minutes, Ca2+ accumulation was initiated in spruce with increased cytosolic and nuclear Ca2+ deposits, but not in brome grass. On 8 Sept. 1997, Ca2+ accumulation occurred in the cytosol of brome grass. This followed a drop in ambient temperature to 12 °C. Cytosolic and nuclear Ca2+ deposits continued to increase in spruce. Controlled experiments confirmed that it was the low temperature, not shortening daylength, that triggered Ca2+ accumulation in brome grass. High cytosolic and nuclear Ca2+ concentrations lasted about three months in spruce from early August to early November. However, the high cytosolic and nuclear Ca2+ concentrations in brome grass lasted only about 20 days from early September to the end of the month. During winter and spring, both species had low resting cytosolic and nuclear Ca2+ concentrations. The relationship between the duration of the high cytosolic and nuclear Ca2+ concentrations and the status of the developed dormancy/cold hardiness is discussed in light of current findings.

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