Event Title
Exploring Cranberry Cold Hardiness Using Differential Thermal Analysis
Start Date
29-8-2017 12:00 PM
End Date
29-8-2017 1:15 PM
Description
Abstract:
To date, cranberry terminal bud cold hardiness has been assessed by controlled freezing tests where levels of damage are evaluated from tissue samples exposed to a range of predetermined sub-freezing temperatures. As in many woody plant buds, freezing stress damage in cranberry is variable across different structures of the bud, often making evaluation challenging. The buds of many woody plant species survive freezing stress by the mechanism of supercooling, the maintenance of water in the liquid state in specific tissues to temperatures below 0°C. The eventual freezing of this supercooled water is lethal to the tissue. The exotherm released from this phase change of water is detectable by the technique of differential thermal analysis (DTA). As part of a larger study on cranberry bud cold hardiness changes concurrent with the plant’s transitions into and out of endodormancy, our initial objective has been to assess the supercooling capability of cranberry buds and the applicability of DTA to quantify this phenomenon. The study was conducted with samples of ‘Stevens’ and ‘HyRed’ collected weekly from two farms in central Wisconsin from ice-off until bud swell in early 2017. Eleven DTA tests were run in custom-built equipment, with controlled freezing tests also performed on the last four sample dates. Low temperature exotherms (LTEs) were detected, supporting the hypothesis that cranberry bud tissue supercools. However, the observed number of LTEs was lower than expected, being detected in only 20 to 40% of the total number of buds tested on a given date (n = 90 to 100). Based on these results, LT10, LT50, and LT90 values were calculated. Over the course of the sampling period, the range of LT50 values remained stable (from -11.3 to -7.3 °C in ‘HyRed’ and from -12.7 to -5.8 °C in ‘Stevens’ ) and did not fluctuate in response to changes in air temperature or the observed variations in leaf pigments. This is in contrast with the results of our controlled freezing tests and those of Workmaster et al. (2006) where LT50 values by showed important shifts from tight bud to bud swell. We are considering technical and physiological explanations for the reduced number of LTEs. Despite efforts to maximize equipment sensitivity, technical challenges may remain. Alternatively, changes in water relations of many woody plant buds occur in response to both endodormancy and prolonged exposure to freezing temperatures. These changes are known to involve the mobilization of water from primordia to other organs, such as bud scales, increasing the ability of primordia to supercool, a process known as extraorgan freezing. Additionally, anatomical observations support this freezing stress survival hypothesis in cranberry buds.
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Recommended Citation
Villouta, Camilo; Workmaster, Beth Ann; Bolivar-Medina, Jenny; and Atucha, Amaya, "Exploring Cranberry Cold Hardiness Using Differential Thermal Analysis" (2017). North American Cranberry Researcher and Extension Workers Conference. 6.
https://scholarworks.umass.edu/nacrew/2017/posters/6
Exploring Cranberry Cold Hardiness Using Differential Thermal Analysis
Abstract:
To date, cranberry terminal bud cold hardiness has been assessed by controlled freezing tests where levels of damage are evaluated from tissue samples exposed to a range of predetermined sub-freezing temperatures. As in many woody plant buds, freezing stress damage in cranberry is variable across different structures of the bud, often making evaluation challenging. The buds of many woody plant species survive freezing stress by the mechanism of supercooling, the maintenance of water in the liquid state in specific tissues to temperatures below 0°C. The eventual freezing of this supercooled water is lethal to the tissue. The exotherm released from this phase change of water is detectable by the technique of differential thermal analysis (DTA). As part of a larger study on cranberry bud cold hardiness changes concurrent with the plant’s transitions into and out of endodormancy, our initial objective has been to assess the supercooling capability of cranberry buds and the applicability of DTA to quantify this phenomenon. The study was conducted with samples of ‘Stevens’ and ‘HyRed’ collected weekly from two farms in central Wisconsin from ice-off until bud swell in early 2017. Eleven DTA tests were run in custom-built equipment, with controlled freezing tests also performed on the last four sample dates. Low temperature exotherms (LTEs) were detected, supporting the hypothesis that cranberry bud tissue supercools. However, the observed number of LTEs was lower than expected, being detected in only 20 to 40% of the total number of buds tested on a given date (n = 90 to 100). Based on these results, LT10, LT50, and LT90 values were calculated. Over the course of the sampling period, the range of LT50 values remained stable (from -11.3 to -7.3 °C in ‘HyRed’ and from -12.7 to -5.8 °C in ‘Stevens’ ) and did not fluctuate in response to changes in air temperature or the observed variations in leaf pigments. This is in contrast with the results of our controlled freezing tests and those of Workmaster et al. (2006) where LT50 values by showed important shifts from tight bud to bud swell. We are considering technical and physiological explanations for the reduced number of LTEs. Despite efforts to maximize equipment sensitivity, technical challenges may remain. Alternatively, changes in water relations of many woody plant buds occur in response to both endodormancy and prolonged exposure to freezing temperatures. These changes are known to involve the mobilization of water from primordia to other organs, such as bud scales, increasing the ability of primordia to supercool, a process known as extraorgan freezing. Additionally, anatomical observations support this freezing stress survival hypothesis in cranberry buds.
This poster is not available for downloading.