After-effects of drought-related winter stress in previous and current year stems of Vaccinium myrtillus L.

The influence of drought-related winter stress on growth, oxidative responses and possible after-effects in previous and current year stems of bilberry (Vaccinium myrtillus L.) was studied in field conditions favorable for desiccation in winter. Bilberry plants were subjected to low temperatures, drought and irradiance under either grey or transparent plates in the absence of snow. Control plants wintered below a snow cover, as bilberry is susceptible to wintertime drought on account of its strategy to winter under snow. Bud phenology was observed early in the growing season and stem elongation was measured in autumn. Tissue water content, lipid peroxidation, anthocyanins, photosynthetic pigments, soluble proteins and activities of glutathione S-transferase and glutathione reductase were monitored during winter dormancy, onset of the growing season, active growth and frost hardening. Metabolic activity was delayed with regard to pigments, antioxidant enzymes and soluble proteins, bud burst was retarded and stem elongation was reduced in the plants that wintered without snow. The plants that wintered under snow showed the best annual stem growth, which was due to the high water content of their previous year stems, resulting in a low level of stress in their current year stems. Not only the previous year stems that were exposed to wintertime stress, but also new growth responded to the stress experienced by the plants in winter, indicating an after-effect of stress that plants were able to sense long after the ceasing of stress.