Lyons Tom, Ollerenshaw John H, Barnes Jeremy D
1 Air Pollution Laboratory, Department of Agricultural and Environmental Science, Ridley Building, The University, Newcastle Upon Tyne NE1 7RU, UK.
New Phytol. 1999 Feb;141(2):253-263. doi: 10.1046/j.1469-8137.1999.00338.x.
The aim of this work was to examine the correspondence between apoplastic/symplastic antioxidant status and previously reported plant age-related shifts in the ozone (O ) resistance of Plantago major L. Seed-grown plants were fumigated in duplicate controlled environment chambers with charcoal/Purafil?-filtered air (CFA) or CFA plus 70 nmol mol O for 7 h d over a 42 d period. Measurements of stomatal conductance and antioxidants were made after 14, 28 and 42 d fumigation, on leaves at an equivalent stage of development (youngest fully expanded leaf, measured c. 9 d after emergence). Ozone exposure resulted in a similar decline in stomatal conductance across plant ages, indicating that increases in O resistance with plant age were mediated through changes in the tolerance of leaf tissue rather than enhanced pollutant exclusion. Leaf apoplastic washing fluid was found to contain 'unspecific' peroxidase, ascorbate peroxidase, superoxide dismutase and ascorbate, but not glutathione and the enzymes required to facilitate the regeneration of ascorbate from its oxidized forms. A weak induction in the activity of certain symplastic antioxidants was found after 14 d O fumigation, despite a lack of visible symptoms of injury, but shifts in symplastic antioxidant enzyme activity were not consistent with previously observed increases in resistance to O with plant age. By contrast, changes in 'unspecific' peroxidase activity and in the small pool of ascorbate in the leaf apoplast were found to accompany age-related shifts in O resistance. It is concluded that constituents of the leaf apoplast may constitute a potentially important front line defence against O .
本研究旨在探讨大车前草质外体/共质体抗氧化状态与先前报道的与植物年龄相关的臭氧（O₃）抗性变化之间的对应关系。用种子培育的植株在两个重复的可控环境舱中，用经木炭/Purafil®过滤的空气（CFA）或CFA加70 nmol mol⁻¹ O₃熏蒸，每天熏蒸7小时，持续42天。在熏蒸14、28和42天后，对处于同等发育阶段（最幼嫩的完全展开叶，在叶片出现后约9天测量）的叶片进行气孔导度和抗氧化剂测量。臭氧暴露导致不同年龄植株的气孔导度出现类似下降，这表明随着植物年龄增长，对O₃抗性的增加是通过叶片组织耐受性的变化介导的，而非增强了对污染物的排除。发现叶片质外体洗涤液中含有“非特异性”过氧化物酶、抗坏血酸过氧化物酶、超氧化物歧化酶和抗坏血酸，但不含谷胱甘肽以及将抗坏血酸从氧化形式再生所需的酶。尽管在O₃熏蒸14天后未观察到明显的损伤症状，但发现某些共质体抗氧化剂的活性有微弱诱导，不过共质体抗氧化酶活性的变化与先前观察到的随着植物年龄增长对O₃抗性增加不一致。相比之下，发现“非特异性”过氧化物酶活性和叶片质外体中少量抗坏血酸的变化与与年龄相关的O₃抗性变化相伴。得出的结论是，叶片质外体的成分可能构成对O₃潜在重要的一线防御。
