ACCELERATED DEHARDENING IN BILBERRY (VACCINIUM-MYRTILLUS L.) INDUCED BY A SMALL ELEVATION IN AIR-TEMPERATURE

The effect of climatic warming on the dehardening potential of bilberr y (Vaccinium myrtillus L.) in a northern boreal environment (65 degree s N) was studied. Natural stands of bilberry were heated artificially in winter. No reference point for the heating was set, since the purpo se was to follow the fluctuations in ambient air temperatures. These w ere 2-3 degrees C higher in the heated plots than in the control plots from October to May. Frost resistance (LT50) and the pH of cell effus ate were monitored throughout. Bud phenology was assessed in May and r elated to various biochemical analyses, including glucose,fructose, su crose, starch and total and reduced glutathione. Frost resistance star ted to decrease earlier in the heated plants, as did the pH of the cel l effusate. Bud phenology was in accordance with the LT50 and pH resul ts, since new growth had emerged in the heated plants by the beginning of May, when the controls still displayed dormancy. Concentrations of glucose, fructose and sucrose were significantly lower in the heated bilberries while concentrations of starch were higher. The heated plan ts also exhibited the lowest glutathione concentrations, but the diffe rence was only marginal. The redox state of glutathione showed no diff erence between the treatments. The results suggest that a small elevat ion in air temperature can accelerate dehardening in the bilberry. It is thus concluded that climatic warming may entail a real risk of earl y dehardening and further frost damage for the bilberry. (C) 1998 Else vier Science Ltd. All rights reserved.