The aim of this work was to assess whether or not oxidative stress
had developed in a dwarf shrub bilberry
(Vaccinium myrtillus L.) under long-term exposure to enhanced
levels of ultraviolet-B (u.v.-B) radiation. The
bilberry plants were exposed to increased u.v.-B representing a 15% stratospheric
ozone depletion for seven full
growing seasons (1991–1997) at Abisko, Swedish Lapland (68°N).
The oxidative stress was assessed on leaves and
stems by analysing ascorbate and glutathione concentrations, and activities
of the closely related enzymes
ascorbate peroxidase (EC 188.8.131.52) and glutathione reductase (EC 184.108.40.206).
The affects of autumnal leaf
senescence and stem cold hardening on these variables were also considered.
The results showed that the treatment
caused scarcely any response in the studied variables, indicating that
u.v.-B flux representing a 15% ozone
depletion under clear sky conditions is not sufficient to cause oxidative
stress in the bilberry. It is suggested that
no strain was evoked since adaptation was possible under such u.v.-B increases.
The studied variables did,
however, respond significantly to leaf senescence and especially to stem