Saurer Matthias, Maurer Stefan, Matyssek Rainer, Landolt Werner, Günthardt-Goerg Madeleine S, Siegenthaler Ulrich
Paul Scherrer Institute, CH-5232, Villigen, Switzerland.
Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasee 111, CH-8903, Birmensdorf ZH, Switzerland.
Oecologia. 1995 Sep;103(4):397-406. doi: 10.1007/BF00328677.
In the cellulose of stems and leaves, δC was investigated in a birch clone (Betula pendula), which was exposed throughout the growing season to either <3 (control) or 90/40 nl O 1 (day/night). Each regime was split into plants under high or low nutrient supply. δC was increased (becoming less negative), in stems rather than leaves, by both high nutrition (+2‰) and O stress (+1‰). Whereas high nutrition raised the wateruse efficiency (WUE) while lowering the CO concentration in the inner leaf air space (c ), WUE decreased and c increased under O stress. Therefore, only the nutritional effect on the carbon isotope fractionation was reproduced by the model of Farquhar et al. (1982) which estimates WUE by means of δC based on c . c was not biased by 'patchiness' in respect to stomatal opening. The latter was verified by microscopical analysis and the complete water infiltration of the birch leaves through the stomata, independent of the diurnal course of the leaf conductance for water vapour. Under low nutrient supply, the activity of phosphoenol pyruvate carboxylase (PEPC) was roughly doubled by ozone to about 1.3% of the total carboxylation capacity (by PEPC + rubisco), and was increased to 1.7% under high nutrition. The fractionation model, extended to account for varying activities of the carboxylating enzymes, indicated that stimulated PEPC was the cause of elevated δC, although c was increased under O stress. The stimulation of PEPC and, as a consequence, elevated δC are discussed as part of a whole-plant acclimation to O stress.
在茎和叶的纤维素中，对一个桦树无性系（垂枝桦）的δC进行了研究，该无性系在整个生长季节暴露于<3（对照）或90/40 nl O₂（日/夜）环境中。每种处理方式又分为高养分供应或低养分供应的植株。高养分（+2‰）和O₃胁迫（+1‰）均使茎而非叶中的δC升高（负值减小）。高养分提高了水分利用效率（WUE），同时降低了叶内空气间隙中的CO₂浓度（c），而在O₃胁迫下WUE降低且c升高。因此，Farquhar等人（1982）的模型仅再现了营养对碳同位素分馏的影响，该模型基于c通过δC估算WUE。c不受气孔开放“不均匀性”的影响。通过显微镜分析以及桦树叶通过气孔完全被水浸润得以验证，这与叶片水蒸气导度的日变化过程无关。在低养分供应下，磷酸烯醇式丙酮酸羧化酶（PEPC）的活性被臭氧大致提高了一倍，达到总羧化能力（PEPC + 核酮糖-1,5-二磷酸羧化酶）的约1.3%，在高养分条件下则增加到1.7%。扩展以考虑羧化酶活性变化的分馏模型表明，尽管在O₃胁迫下c升高，但PEPC的激活是δC升高的原因。PEPC的激活以及随之而来的δC升高被认为是植物对O₃胁迫的整体适应性的一部分进行了讨论。
