BACKGROUND & AIMS:
:Three-year-old beech (Fagus sylvatica) seedlings growing in containers were placed into the sun and shade crown of a mature beech stand exposed to ambient (1 x O(3)) and double ambient (2 x O(3)) ozone concentrations at a free-air exposure system ("Kranzberg Forst", Germany). Pigments, alpha-tocopherol, glutathione, ascorbate, and gas exchange were measured in leaves during 2003 (a drought year) and 2004 (an average year). Sun-exposed seedlings showed higher contents of antioxidants, xanthophylls, and beta-carotene and lower contents of chlorophyll, alpha-carotene, and neoxanthin than shade-exposed seedlings. In 2003 sun-exposed seedlings showed higher contents of carotenoids and total glutathione and lower net photosynthesis rates (A(max)) compared to 2004. O(3) exposure generally affected the content of chlorophyll, the xanthophyll cycle, and the intercellular CO(2) concentration (c(i)). Seedlings differed from the adjacent adult trees in most biochemical and physiological parameters investigated: Sun exposed seedlings showed higher contents of alpha-tocopherol and xanthophylls and lower contents of ascorbate, chlorophyll, neoxanthin, and alpha-carotene compared to adult trees. Shade exposed seedlings had lower contents of xanthophylls, alpha-carotene, and alpha-tocopherol than shade leaves of old-growth trees. In 2003, seedlings had higher A(max), stomatal conductance (g(s)), and c(i) under 2 x O(3) than adult trees. The results showed that shade acclimated beech seedlings are more sensitive to O(3), possibly due to a lower antioxidative capacity per O(3) uptake. We conclude that beech seedlings are uncertain surrogates for adult beech trees.
背景与目标:
:将在容器中生长的三岁山毛榉(Fagus sylvatica)幼苗放在暴露于环境(1 x O(3))和两倍环境(2 x O(3))的成熟山毛榉林的阳光和树荫树冠下自由空气暴露系统中的臭氧浓度(德国“ Kranzberg Forst”)。在2003年(干旱年)和2004年(平均年)期间,对叶片中的色素,α-生育酚,谷胱甘肽,抗坏血酸和气体交换进行了测量。暴露在阳光下的幼苗比暴露在阴影下的幼苗显示更高的抗氧化剂,叶黄素和β-胡萝卜素含量,而叶绿素,α-胡萝卜素和新黄嘌呤的含量更低。与2004年相比,2003年受阳光照射的幼苗显示出较高的类胡萝卜素含量和总谷胱甘肽含量,净光合速率较低(A(max))。O(3)暴露通常会影响叶绿素含量,叶黄素循环和细胞间CO( 2)浓度(c(i))。在所调查的大多数生化和生理参数上,幼苗与相邻的成年树不同:与成年树相比,暴露在阳光下的幼苗显示出较高的α-生育酚和叶黄素含量,而抗坏血酸盐,叶绿素,新黄嘌呤和α-胡萝卜素的含量较低。暴露于阴凉处的幼苗的叶黄素,α-胡萝卜素和α-生育酚的含量低于老树的阴暗叶。在2003年,幼苗在2 x O(3)下具有比成年树更高的A(max),气孔导度(g(s))和c(i)。结果表明,适应阴凉的山毛榉幼苗对O(3)更为敏感,这可能是由于每摄取O(3)的抗氧化能力较低。我们得出的结论是,山毛榉幼苗对于成年的山毛榉树是不确定的替代物。