Physics Institute, University of Bern, CH-3012 Bern, Switzerland.
Plant Physiol. 1991 Sep;97(1):313-6. doi: 10.1104/pp.97.1.313.
The relative composition of stable carbon isotopes, delta(13)C, was determined in flag leaves and grain of spring wheat (Triticum aestivum L. cv Albis) grown in open-top field fumigation chambers and exposed to different O(3) levels during the growing season. The aim of the study was to establish exposure-response relationships for the radiation-weighted seasonal mean O(3) concentration and delta(13)C (relative deviation of the (13)C/(12)C ratio) values of the two plant parts. Samples were collected at harvest in 1986, 1987, and 1988. With increasing O(3) concentration, delta(13)C values increased (became less negative) proportionally. Year to year delta(13)C differences at equivalent O(3) concentrations were small. The shift in delta(13)C caused by O(3) was more pronounced in grain than in leaves. According to models of (13)C discrimination in C(3) plants, these results indicate increasing limitation of photosynthesis by CO(2) diffusion relative to limitation by carboxylation with increasing O(3) exposure. This conclusion is not in agreement with results from gas exchange analysis. Water use efficiency in green flag leaves tended to decrease with increasing O(3), indicating a dominating effect of O(3) on CO(2) carboxylation.
在开放顶篷田间熏气室中种植的春小麦（Triticum aestivum L. cv Albis）的旗叶和籽粒中，测定了稳定碳同位素的相对组成，δ（13）C。本研究的目的是建立辐射加权季节平均 O（3）浓度和两个植物部分的δ（13）C（（13）C/（12）C 比值的相对偏差）值之间的暴露-反应关系。在 1986、1987 和 1988 年收获时采集了样本。随着 O（3）浓度的增加，δ（13）C 值呈比例增加（变得更负）。在等效 O（3）浓度下，每年的 δ（13）C 差异较小。与叶片相比，O（3）引起的 δ（13）C 变化在籽粒中更为明显。根据 C（3）植物中（13）C 歧视的模型，这些结果表明，随着 O（3）暴露的增加，CO（2）扩散对光合作用的限制相对于羧化作用的限制越来越大。这一结论与气体交换分析的结果不一致。随着 O（3）的增加，绿色旗叶的水分利用效率趋于降低，表明 O（3）对 CO（2）羧化作用的主导作用。
