Search Results

You are looking at 1 - 3 of 3 items for :

  • Author or Editor: Cindy L. Flinn x
  • Journal of the American Society for Horticultural Science x
Clear All Modify Search

Differential thermal analysis (DTA) was used to study the freezing behavior of `Berkeley' blueberry (Vaccinium corymbosum L.) flower buds at cooling rates of 10, 5, and 2C/hour. Experiments were conducted at various stages of hardiness on excised and attached (5 cm of stem) buds. The presence and number of low-temperature exotherms (LTEs) in hardy buds generally increased when analyses were conducted using faster cooling rates with excised buds. The number of LTEs detected in individual buds did not correlate (r 2 = 0.27) with the number of injured florets. The inability to detect LTEs in buds attached to stem segments and cooled at 2C/hour indicates that DTA cannot reliably estimate blueberry flower-bud hardiness in field plantings.

Free access

The accumulation of total soluble sugars (TSS) and starch and their relationship to flower bud hardiness were studied in three Forsythia taxa: Forsythia ×intermedia `Spectabilis', Forsythia ×intermedia `Lynwood', and F. suspensa. Taxon hardiness was based on the mean temperature at which low temperature exotherms (LTEs) occurred during thermal analysis. Ethanol-extracted soluble sugars were quantified with anthrone, and starch was enzymatically digested and quantified with Trinder reagent. Qualitative changes in sugar content were determined with high-performance liquid chromatography and co-chromatography of authentic standards. Quantitative and qualitative changes in sugar content, similar for the three taxa, were observed in conjunction with fluctuations in flower bud hardiness, although neither TSS nor starch were correlated with mean LTE temperature. TSS was higher in acclimated than nonacclimated buds. However, after deacclimation began, sugars continued to increase with mean LTE temperature. Buds lacked starch except for a brief period during deacclimation. Galactose, stachyose, raffinose, and an unidentified carbohydrate were positively correlated with hardiness (P = 0.005, 0.001, 0.005, and 0.001, respectively).

Free access

The location of ice crystals and their relationship to xylem vessels was studied in nonacclimated and acclimated `Berkeley' blueberry (Vaccinium corymbosum L.) flower buds. Light microscopy and low-temperature scanning electron microscopy (SEM) were used to detect ice crystals in the bud scales, floret scales, and bracts of dormant flower buds that had been frozen to -15C. No evidence of ice formation was observed in rachises, pedicels, and organs in florets when buds that had been fixed while frozen at -5C were examined with conventional SEM. This indicated that dormant buds underwent extraorgan freezing as a survival mechanism. Ice formation was not uniform in nonacclimated or deacclimated buds, although it was more prevalent in both than in acclimated buds. Large ice crystals were found in the ovaries of freeze-stressed nonacclimated buds. In deacclimated freeze-stressed buds, ice was found in the petals, rachises, pedicels, and ovaries. To determine whether this ice distribution pattern was correlated with the presence of mature xylem vessels, cleared flower buds were stained with basic fuchsin, which revealed the intact network of lignified elements. In nonacclimated buds (20 Sept.), mature xylem vessels extended through the rachises, connecting the bud scales with the floret scales and through the pedicels into the corollas of the florets. Although vascular development occurred in dormant buds, the greatest proliferation of vessels in the ovaries, petals, and sepals occurred coincident to the appearance of ice in these organs and the loss of hardiness.

Free access