Physiological Damages and Biochemical Alleviation to Ozone Toxicity in Five Species of genus Acer

摘要

We investigated physiological damages and biochemical alleviation of five species of genus Acer under ozone fumigation in order to assess their tolerant ability against ozone toxicity. At the end of 150 ppb O_3 fumigation, photosynthetic characteristics were measured, and chlorophyll contents, malondialdehyde (MDA) and antioxidative enzyme activities were analyzed in the leaves of five maple trees (Acer buergerianum, A. ginnala, A. mono, A. palmatum, and A. palmatum var. sanguineum). The reduction ofchlorophyll (chl) a in ozone-exposed plants was 16.8% (A. buergerianum) to 26.7% (A. ginnala) of control plants. For the content of chl b, A. ginnala and A. palmatum var. sanguineum represented the high reduction of 26.3% and 23.6%, respectively. The highest reduction on the chl a:b ratio was observed in the leaves of A. palmatum. The reduction of net photosynthesis in five species varied from 2.4% to 37.6%. Among five species, A. ginnala showed remarkable reduction (37.6%) for net photosynthesis in comparison with control. Carboxylation efficiency differed significantly (P < 0.05) among species and between control and ozone treatment. The reduction of carboxylation efficiency was the highest in the leaves of A. ginnala (44.7%). A. palmatum var. sanguineum showed the highest increase (41.7%) for MDA content. The highest increase of superoxide dismutase (SOD) activity represented in A. palmatum (26.1%) and the increase of ascorbate peroxidase (APX) activity ranged from 16.5% (A. ginnala) to 49.1% (A.palmatum var. sanguineum). A. mono showed the highest increase (376.6%) of glutathione reductase (GR) activity under ozone fumigation and A. buergerianum also represented high increase (42.3%) of GR activity. Catalse (CAT) activity increased in the leaves of A. ginnala, A. palmatun and A. palmatum var. sanguineum under ozone exposure, whereas A. buergerianum and A. mono decreased in comparison with control plants. In conclusion, physiological markers such as chlorophyll content and photosynthesis that responded sensitively to O_3 in maple frees were considered as the very important indicators hi order to evaluate the tolerance against O_3 stress, and parameters were closely related with each other. Among antioxidative enzymes, SOD and APX might be contributed to alleviate to O_3 toxicity through the increase of activity in all maple trees. Therefore, these compounds can be used as a biochemical maker to assess the stress tolerance to O_3.