Antioxidants and Protective Pigments of Pinus ponderosa Needles at Gradients of Natural Stresses and Ozone in the San Bernardino Mountains in California

Yverdon

1999

S. 113-120

2 Abb., 2 Tab., 24 Lit. Ang.

Bandaufführung

9998S

136349

At the San Berndardino Mountains, California, a well documented gradient of ozone pollution overlays a natural stress gradient from mesic to dry and from lower elevation to higher elevation sites. In contrast to gradient studies in European regions, the highest ambient ozone levels are observed at low elevation and more mesic locations. In the present study, antioxidative and photoprotective systems in Pinus ponderosa needles were investigated at three plots - DW (1725 m, high ozone impact, mesic site), SW (1200 m, clean air, xeric site) and CO (above 2000 m, clean air and xeric site). Needles from the CO site contained significantly more total GSH (500 vs 300 nmolg-1dw in c needles), less a-carotene (6-10 vs 14-19 ug mg-1 total chlorophyll) and Chlorophyll (1.7-2 vs 2.5-2.6 mg g-1 dw in c + 1 needles) than those at the DW site. Furthermore, their xanthophyll cycle pool was in a more de-epoxidized state at midday (up to 60% in c needles), and the carotenoid/chlorophlls ratios were generally higher. These patterns correspond to those observed at higher elevation plots in the Alps. On the other hand, needles from the high ozone site (DW) had a higher proportion of GSSG, indicating the onset of biochemical injury to needles. Needles from the SW site had intermediate proportions of GSSG. The results show the potential of environmental stressors to induce antioxidative and photoprotective responses in the absence of elevated ozone concenfrations, but support the oxidative effects of ozone injury to ponderosa pine.