Department of Environmental and Biological Sciences, Natural Products Laboratory, University of Eastern Finland (UEF), P.O. Box, 111, FI-80101, Joensuu, Finland.
Department of Environmental and Biological Sciences, Natural Products Laboratory, University of Eastern Finland (UEF), P.O. Box, 111, FI-80101, Joensuu, Finland; Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway.
Plant Physiol Biochem. 2018 May;126:55-62. doi: 10.1016/j.plaphy.2018.02.025. Epub 2018 Mar 2.
The accumulation of flavonoids on the leaf surface is a well-characterized protective mechanism against UV-B radiation. Other protective mechanisms, such as the induction of antioxidative enzymes and peroxidase-mediated lignification may also be important. The effects of UV-B radiation have mainly been considered in short-term studies, whereas ecologically more relevant long-term field studies are still rare. Here we examined the effects of long-term exposure to enhanced UV-B radiation on the activities of two antioxidative enzymes, polyphenol oxidase (PPO; EC 1.10.2.2 and EC 1.14.18.1) and guaiacol peroxidase (POD; EC 1.11.1.7), as well as the phenolic concentrations in two sexes of the dioecious species, Salix myrsinifolia. After three consecutive growth seasons with enhanced UV-B radiation, we found that PPO activity was decreased by UV radiation in male plants, which might explain their lower UV-B tolerance when compared to female plants. In addition, male plants had higher specific activity than did female plants under ambient conditions, supporting the idea that males of S. myrsinifolia are generally more growth-oriented than females. By contrast, neither UV treatment nor sex had significant effects on the POD activities of willows. Gender differences in the concentrations of phenolic compounds are in line with the general concept that males are less well defended than females. We suggest that the inability to increase PPO and POD activity, along with lower accumulation of UV-B absorbing compounds under UV-B exposure, might be one of the reasons why males had thinner leaves and were less tolerant of UV-B than were females.
叶片表面类黄酮的积累是植物抵御 UV-B 辐射的一种特征性保护机制。其他保护机制，如抗氧化酶的诱导和过氧化物酶介导的木质化，也可能很重要。UV-B 辐射的影响主要在短期研究中被考虑，而在生态上更相关的长期野外研究仍然很少。在这里，我们研究了长期暴露在增强的 UV-B 辐射下对两种抗氧化酶，多酚氧化酶（PPO；EC 1.10.2.2 和 EC 1.14.18.1）和愈创木酚过氧化物酶（POD；EC 1.11.1.7）的活性以及两种性别雌雄异株的柳属植物（Salix myrsinifolia）酚类浓度的影响。经过三个连续的增强 UV-B 辐射的生长季节，我们发现 PPO 活性在雄性植物中被 UV 辐射所降低，这可能解释了与雌性植物相比，雄性植物对 UV-B 的耐受性较低。此外，在环境条件下，雄性植物的比活性高于雌性植物，这支持了柳属植物雄性通常比雌性更注重生长的观点。相比之下，UV 处理或性别对柳树的 POD 活性均没有显著影响。酚类化合物浓度的性别差异与一般概念一致，即雄性的防御能力不如雌性。我们认为，无法增加 PPO 和 POD 活性，以及在 UV-B 暴露下积累较少的吸收 UV-B 的化合物，可能是雄性叶片较薄且比雌性更不耐受 UV-B 的原因之一。
