Severe salt stress in Vaccinium myrtillus (L.) in response to Na+ ion toxicity

NaCl is spread on the northern roads as a winter de-icing agent. Na+ stress may occur in roadside forests especially during growing season, because snowmelt increases Na+ concentrations in the roadside forest soil. To simulate summertime Na+ stress and its effect on viability and anthocyanin concentrations, bilberry (Vaccinium myrtillus L.) plants were subjected to NaCl (0, 6, 30 and 60 g m−2) in a boreal mesic heath forest in northern Finland (65°N). It was hypothesised that Na+ stress decreases tissue water content (TWC) in below- and aboveground stems, where resulting water stress increases anthocyanin level for osmotic regulation. Uptake of Na+ from the soil to the below- and aboveground stems was detected by a fast sequential atomic absorption spectrometry. Na+ accumulated in belowground stems, but it was translocated into the aboveground stems to a lesser extent. At the end of the growing season, TWC increased in belowground stems and decreased in aboveground stems. Also anthocyanin concentrations decreased in aboveground stems. The viability of the aboveground stems decreased to 30% along with the Na+ accumulation. Despite the strong viability response in aboveground stems, TWC was constant in the middle of the growing season and decreased relatively little at the end of the growing season. It is thus proposed that direct effect of Na+ ions, rather than Na+-induced water stress, is the primary reason behind the strong viability response and a severe salt stress in bilberry.

► Na+ exposure decreases the viability of the aboveground stems in bilberry.
► Direct toxicity of Na+ ions, rather than Na+-induced water stress, is the primary reason behind the strong viability response.
► Anthocyanin concentrations decrease in response to Na+ ion toxicity.