2019 ASHS Annual Conference

Large changes in cranberry bud freezing stress survival occur during the dormant period. However, the timing and exact nature of these changes are not well understood due to the lack of information in physiological processes of dormancy, temperature acclimation and deacclimation, as well as the anatomical changes in and around the terminal bud of the cranberry plant. The objective of this study was to elucidate the freezing stress survival strategy of terminal cranberry buds, and to evaluate specific bud structure responses to freezing stresses for the purpose of developing a standardized methodology to evaluate cold hardiness. Controlled freezing test (CFT), differential thermal analysis (DTA), and histological evaluation of bud structures were performed during fall and early winter. Our findings show that cranberry terminal buds do not generate detectable low temperature exotherms (LTEs). Through the use of a novel methodology of visual evaluation of freezing injury in buds subjected to CFT, we observed a gradual increase in the damage severity of different tissues within the terminal bud as temperatures decreased. The range of damage in bud structures changed as fall progressed, and a distinctive increase in bud cold hardiness was observed in the month of October. Large voids were identified in bud scales in early winter, which are likely the result of ice formation during freezing events. The results of this study suggest that cranberry terminal buds likely withstand periods of freezing stress by extraorgan freezing.