Oksanen E, Kontunen-Soppela S, Riikonen J, Peltonen P, Uddling J, Vapaavuori E
Department of Biology, University of Joensuu, P.O. Box 111, 80101 Joensuu, Finland.
Plant Biol (Stuttg). 2007 Mar;9(2):191-6. doi: 10.1055/s-2006-924176. Epub 2006 Jul 24.
Ozone sensitivity of silver birch ( BETULA PENDULA Roth) has been thoroughly investigated since early 1990's in Finland. In our long-term open-field experiments the annual percentage reduction in basal diameter and stem volume increment were the best non-destructive growth indicators for ozone impact when plotted against AOTX. Remarkable differences in defence strategies, stomatal conductance, and defence compounds (phenolics), clearly indicate that external exposure indices are ineffective for accurate risk assessment for birch. For flux-based approaches, site-specific values for G(max) and G(dark) are necessary, and determinants for detoxification capacity, ageing of leaves, and cumulative ozone impact would be needed for further model development. Increasing CO(2) seems to counteract negative ozone responses in birch, whereas exposure to spring time frost may seriously exacerbate ozone damage in northern conditions. Therefore, we need to proceed towards incorporating the most important climate change factors in any attempts for ozone risk assessment.
自20世纪90年代初以来，芬兰对银桦（Betula pendula Roth）的臭氧敏感性进行了全面研究。在我们的长期野外实验中，将基径年减少百分比和茎体积增量与AOTX作图时，它们是臭氧影响的最佳非破坏性生长指标。防御策略、气孔导度和防御化合物（酚类）存在显著差异，这清楚地表明外部暴露指数对于准确评估桦树的风险是无效的。对于基于通量的方法，需要特定地点的G(max)和G(dark)值，并且进一步的模型开发还需要解毒能力、叶片衰老和累积臭氧影响的决定因素。二氧化碳浓度增加似乎可以抵消桦树对臭氧的负面反应，而在北方条件下，春季霜冻可能会严重加剧臭氧损害。因此，在任何臭氧风险评估尝试中，我们都需要将最重要的气候变化因素纳入其中。
