Changes in Carbohydrate Synthesis during Cold Acclimation in Cranberry (Vaccinium macrocarpon)

Cranberry plants tend to increase cold tolerance by synthesizing protective compounds during cold acclimation. The protective compounds are associated with biochemical, structural and physiological changes that occur in the plant during acclimation, however, these have not been fully studied in cranberries. The specific objective of this study was to identify and quantify carbohydrates synthesized by four cranberry var ‘Stevens’, ‘Howes’, ‘Mullica Queen’ and ‘DeMoranville’ during cold acclimation. A completely randomized design experiment replicated four times involving temperature and cultivar treatments, was conducted in a growth chamber. Potted cranberry plants were subjected to gradual decrease in temperature, day length and light intensity: 15˚C day/night at 12-h photoperiod and photosynthetic photon flux density (PPFD) of 500 µmolm^-2s^-1, 6˚C day/night at 10-h photoperiod and PPFD of 250 µmolm^-2s^-1, 2˚C day/night 10-h photoperiod and PPFD of 250 µmolm^-2s^-1 and -2˚C in total darkness for two weeks in each setting. Carbohydrates were extracted from leaf and stem tissues and analyzed using high pressure liquid chromatography (HPLC). Four, total non-structural (TNSC) sugars, sucrose, glucose, fructose and starch were identified in cranberry leaves and stems. There was a significant interaction (p<0.001) between tissue and acclimation temperature, inferring that acclimation temperature influenced leaf and stem tissues differently. Higher TNSC were observed in leaves than stems. Sucrose, glucose and fructose seemed to increase significantly from 15˚C to -2˚C while starch decreased. The increase in total non-structural carbohydrates (TNSC) suggests an enhanced cellular stability which brings about an increase in plant cold hardiness. There were no significant differences between the cranberry cultivars at all temperature settings.