Changes in Levels of a-Tocopherol and Ascorbate in Spruce Needles at Three Low Mountain Sites Exposed to Mg2+-Deficiency and Ozone

T he m ain objective o f this study was the com parison o f changes in levels o f a-tocopherol and ascorbate in needles o f spruce trees w ith various degrees o f dam age at three low m ountain sites. The ascorbate content in needles o f spruce trees w ith various degrees o f dam age differs in the course o f seasons as well as in the absolute level. The antiox idant status was affected m ain­ ly during summer. The content o f ascorbate in needles o f dam aged trees was significantly in­ creased com pared to th a t o f undam aged trees. Despite seasonal and daily fluctuations, the level o f ascorbate seems to be a good ind icator for the degree o f dam age in the case o f sym p­ tom s described as m ontane yellowing. T ogether with an increasing con ten t o f a-tocopherol per chlorophyll, a rise o f ascorbate con ten t indicates enhanced oxidative stress in the needles o f dam aged trees, particularly in summer. A sc/aToc ratios were increased in needles o f dam ­ aged trees. A t the studied sites enhanced oxidative stress could be caused by the com bined action o f M g2+-deficiency, high ozone concentrations and high-light intensity, all inducing an increased production o f radicals in com bination with a reduced photosynthetic capacity.