Homeostatic gas-exchange parameters inferred from C-13/C-12 in tree rings of conifers
Homeostatic gas-exchange parameters inferred from C-13/C-12 in tree rings of conifers
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DOI：
10.1007/bf00328786
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发表时间：
1996-01-01
期刊：
影响因子：
2.7
通讯作者：
Monserud, RA
中科院分区：
文献类型：
--
作者：
Marshall, JD;Monserud, RA
在过去的两个世纪里，大气中的二氧化碳浓度增加了近30%，其中大部分增加(>；5pa)是在过去的60年里。对依赖于C-3光合作用途径的作物的受控环境研究表明，这一幅度的增加将增强净光合作用，降低气孔导度，并增加气孔两端的CO2浓度差，即叶片外的CO2浓度与(c(A)-c(I))内的CO2浓度之差。在这里，我们报告了基于来自三种田间种植的本土针叶树的树轮的稳定同位素组成的证据，证明这些树确实有反应。然而，胞间二氧化碳浓度不仅没有增加，反而向上移动，以适应大气浓度的上升，保持c(A)-c(I)不变。道格拉斯冷杉、黄皮松和西白松之间无明显差异。C(A)-c(I)的值是由树轮综纤维素的稳定碳同位素比值(Delta(13)C)推算出来的，该值调整了综纤维素与全边材之间的千分之0.6-2.6的差异。纤维素提取去除了年轮形成后沉积在树轮中的污染物，并修正了纤维素相对于整个组织的浓缩。然后，根据公布的过去大气三角洲(13)、二氧化碳(2)和二氧化碳浓度的估计，调整了整个边材的值。为了避免将树龄与二氧化碳混淆，1910-1929年和1941-1970年间，当成熟的树木是树苗时，树苗在树木内轮中沉积的纤维素：这样就把树苗比作树苗。在另一项单独的分析中，描述了在树木生命的最初几十年中增量(13)C增加的趋势的幼年效应被量化，而不受来源二氧化碳的影响。这项研究提供了证据，表明针叶树经历了细胞间二氧化碳浓度的调整，保持了c(A)-c(I)的恒定。基于这些结果和其他结果，我们建议c(A)-c(I)，也被称为内在水分利用效率，应该被认为是这些针叶树种的动态平衡气体交换设定点。
The CO2 concentration of the atmosphere has increased by almost 30% in the past two centuries, with most of the increase (> 5 Pa) during the past 60 years. Controlled environment studies of crop plants dependent on the C-3 photosynthetic pathway indicate that an increase of this magnitude would enhance net photosynthesis, reduce stomatal conductance, and increase the difference in CO2 concentration across the stomata, i.e., CO2 concentration outside the leaf to that within (c(a)-c(i)). Here we report evidence, based on stable isotope composition of tree rings from three species of field-grown, native conifer trees; that the trees have indeed responded. However, rather than increasing c(a)-c(i), intercellular CO2 concentrations have shifted upward to match the rise in atmospheric concentrations, holding c(a)-c(i) constant. No differences were detected among Douglas-fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), or western white pine (Pinus monticola). The values of c(a)-c(i) were inferred from stable carbon isotope ratio (delta(13)C) of tree ring holocellulose adjusted for the 0.6-2.6 parts per thousand difference between holocellulose and whole sapwood. The cellulose extraction removed contaminants deposited in the tree ring after it formed and the adjustment corrected for the enrichment of cellulose relative to whole tissue. The whole sapwood values were then adjusted for published estimates of past atmospheric delta(13)CO(2) and CO2 concentrations. To avoid confounding tree age with CO2, cellulose deposited by saplings in the inner rings of trees when the mature trees were saplings, between 1910-1929 and 1941-1970: thus saplings were compared to saplings. In a separate analysis, the juvenile effect, which describes the tendency for delta(13)C to increase in the first decades of a tree's life, was quantified independent of source CO2 effects. This study provides evidence that conifers have undergone adjustments in the intercellular CO2 concentration that have maintained c(a)-c(i) constant. Based on these results and others, we suggest that c(a)-c(i) which has also been referred to as the intrinsic water-use efficiency, should be considered a homeostatic gas-exchange set point for these conifer species.