Schwanz P, Polle A
Albert-Ludwigs-Universität Freiburg, Institut für Forstbotanik und Baumphysiologie, Am Flughafen 17, D-79085 Freiburg, Germany.
J Exp Bot. 2001 Jan;52(354):133-43.
Maritime pine (Pinus pinaster), a drought-avoiding species, contained 2--4-fold lower activities of superoxide dismutase, ascorbate peroxidase, catalase, dehydroascorbate reductase, and glutathione reductase than pendunculate oak (Quercus robur), a drought-tolerant species. The levels of ascorbate, monodehydroascorbate radical reductase activity, and glutathione in pine needles were similar to those in oak leaves. In both species the development of drought stress, characterized by decreasing predawn water potentials, caused gradual reductions in antioxidant protection, increased lipid peroxidation, increased oxidation of ascorbate and glutathione and in pine also significant loss in soluble proteins and carotenoids. These results support the idea that increased drought-tolerance in oak as compared with pine is related to increased biochemical protection at the tissue level. To test the hypothesis that elevated CO(2) ameliorated drought-induced injury, young oak and pine trees acclimated to high CO(2) were subjected to drought stress. Analysis of plots of enzymatic activities and metabolites against predawn water potentials revealed that the drought stress-induced decreases in antioxidant protection and increases in lipid peroxidation were dampened at high CO(2). In pine, protein and pigment degradation were also slowed down. At high CO(2), superoxide dismutase activities increased transiently in drought-stressed trees, but collapsed in pine faster than in oak. These observations suggest that the alleviation of drought-induced injury under elevated CO(2) is related to a higher stability of antioxidative enzymes and an increased responsiveness of SOD to stressful conditions. This ameliorating mechanism existed independently from the effects of elevated CO(2) on plant water relations and is limited within a species-specific metabolic window.
海岸松（Pinus pinaster）是一种避旱树种，其超氧化物歧化酶、抗坏血酸过氧化物酶、过氧化氢酶、脱氢抗坏血酸还原酶和谷胱甘肽还原酶的活性比耐旱树种无梗花栎（Quercus robur）低2至4倍。松针中的抗坏血酸水平、单脱氢抗坏血酸自由基还原酶活性和谷胱甘肽与栎树叶中的相似。在这两个物种中，以黎明前水势降低为特征的干旱胁迫的发展导致抗氧化保护逐渐降低、脂质过氧化增加、抗坏血酸和谷胱甘肽氧化增加，并且在松树中可溶性蛋白质和类胡萝卜素也有显著损失。这些结果支持了这样一种观点，即与松树相比，栎树耐旱性增加与组织水平上生化保护的增加有关。为了验证二氧化碳浓度升高可减轻干旱诱导损伤的假设，使适应高二氧化碳的栎树和松树幼苗遭受干旱胁迫。针对黎明前水势分析酶活性和代谢物的图表显示，在高二氧化碳浓度下，干旱胁迫诱导的抗氧化保护降低和脂质过氧化增加受到抑制。在松树中，蛋白质和色素降解也减缓。在高二氧化碳浓度下，干旱胁迫树木中的超氧化物歧化酶活性短暂增加，但在松树中比在栎树中更快下降。这些观察结果表明，二氧化碳浓度升高缓解干旱诱导损伤与抗氧化酶更高的稳定性以及超氧化物歧化酶对胁迫条件更高的反应性有关。这种改善机制独立于二氧化碳浓度升高对植物水分关系的影响，并且局限于物种特异性代谢窗口内。
