Seasonal patterns of ascorbate in the needles of Scots Pine (Pinus sylvestris L.) trees: Correlation analyses with atmospheric O_3 and NO_2 gas mixing ratios and meteorological parameters

摘要

In the present field study the role of ascorbate in scavenging the harmful atmospheric trace gases O_3 and NO_2 was examined. For this purpose ascorbate contents were determined in needles of adult Scots pine trees (Pinus sylvestris L.) during three consecutive years. Ascorbate contents were correlated with ambient tropospheric O_3 and NO_2 concentrations and with meteorological parameters. The results showed a strong correlation of atmospheric O_3 but not of atmospheric NO_2 concentrations with the apoplastic content of ascorbate during the seasonal course. Ascorbate contents in needle extracts did not correlate with ambient trace gas concentrations. In the apoplastic space, but not in needle extracts ascorbate contents correlate highly significantly with global radiation. From these results it is assumed that apoplastic ascorbate in Scots pine needles is adapted to the actual atmospheric O_3 concentration to mediate immediate detoxification of O_3, while the atmospheric O_3 concentration itself is largely dependent on light intensity.