U. Schmieden et A. Wild, CHANGES IN LEVELS OF ALPHA-TOCOPHEROL AND ASCORBATE IN SPRUCE NEEDLESAT 3 LOW MOUNTAIN SITES EXPOSED TO MG2-DEFICIENCY AND OZONE(), Zeitschrift fur Naturforschung. C, A journal of biosciences, 49(3-4), 1994, pp. 171-180
The main objective of this study was the comparison of changes in leve
ls of a-tocopherol and ascorbate in needles of spruce trees with vario
us degrees of damage at three low mountain sites. The ascorbate conten
t in needles of spruce trees with various degrees of damage differs in
the course of seasons as well as in the absolute level. The antioxida
nt status was affected mainly during summer. The content of ascorbate
in needles of damaged trees was significantly increased compared to th
at of undamaged trees. Despite seasonal and daily fluctuations, the le
vel of ascorbate seems to be a good indicator for the degree of damage
in the case of symptoms described as montane yellowing. Together with
an increasing content of a-tocopherol per chlorophyll, a rise of asco
rbate content indicates enhanced oxidative stress in the needles of da
maged trees, particularly in summer. Asc/alpha Toc ratios were increas
ed in needles of damaged trees. At the studied sites enhanced oxidativ
e stress could be caused by the combined action of Mg2(+)-deficiency,
high ozone concentrations and high-light intensity, all inducing an in
creased production of radicals in combination with a reduced photosynt
hetic capacity.