Kimak Adam, Kern Zoltan, Leuenberger Markus
Climate and Environmental Physics, Physics Institute, University of Bern Bern, Switzerland ; Oeschger Centre for Climate Change Research, University of Bern Bern, Switzerland.
Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences (MTA) Budapest, Hungary.
Front Plant Sci. 2015 Nov 24;6:1008. doi: 10.3389/fpls.2015.01008. eCollection 2015.
Foliar samples were harvested from two oaks, a beech, and a yew at the same site in order to trace the development of the leaves over an entire vegetation season. Cellulose yield and stable isotopic compositions (δ(13)C, δ(18)O, and δD) were analyzed on leaf cellulose. All parameters unequivocally define a juvenile and a mature period in the foliar expansion of each species. The accompanying shifts of the δ(13)C-values are in agreement with the transition from remobilized carbohydrates (juvenile period), to current photosynthates (mature phase). While the opponent seasonal trends of δ(18)O of blade and vein cellulose are in perfect agreement with the state-of-art mechanistic understanding, the lack of this discrepancy for δD, documented for the first time, is unexpected. For example, the offset range of 18 permil (oak veins) to 57 permil (oak blades) in δD may represent a process driven shift from autotrophic to heterotrophic processes. The shared pattern between blade and vein found for both oak and beech suggests an overwhelming metabolic isotope effect on δD that might be accompanied by proton transfer linked to the Calvin-cycle. These results provide strong evidence that hydrogen and oxygen are under different biochemical controls even at the leaf level.
在同一地点从两棵橡树、一棵山毛榉和一棵紫杉上采集了叶片样本，以追踪整个生长季节叶片的发育情况。对叶片纤维素进行了纤维素产量和稳定同位素组成（δ(13)C、δ(18)O和δD）分析。所有参数都明确界定了每个物种叶片扩展过程中的幼年期和成熟期。伴随的δ(13)C值变化与从再利用碳水化合物（幼年期）到当前光合产物（成熟期）的转变一致。虽然叶片和叶脉纤维素的δ(18)O呈现相反的季节性趋势，这与目前最先进的机理理解完全一致，但首次记录到的δD不存在这种差异却出乎意料。例如，δD中18‰（橡树叶脉）到57‰（橡树叶片）的偏移范围可能代表了一个从自养过程到异养过程的由过程驱动的转变。在橡树和山毛榉的叶片和叶脉中发现的共同模式表明，δD受到压倒性的代谢同位素效应影响，这可能伴随着与卡尔文循环相关的质子转移。这些结果提供了有力证据，表明即使在叶片水平上，氢和氧也受到不同的生化控制。
