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C4 photosynthetic isotope exchange in NAD-ME- and NADP-ME-type grasses

机译：NAD-ME-型和NADP-ME-型草中C 4 光合同位素的交换

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Monitoring photosynthetic isotope exchange is an important tool for predicting the influence of plant communities on the global carbon cycle in response to climate change. C4 grasses play an important role in the global carbon cycle, but their contribution to the isotopic composition of atmospheric CO2 is not well understood. Instantaneous measurements of 13CO2 (Δ13C) and C18OO (Δ18O) isotope exchange in five NAD-ME and seven NADP-ME C4 grasses have been conducted to investigate the difference in photosynthetic CO2 isotopic fractionation in these subgroups. As previously reported, the isotope composition of the leaf material (δ13C) was depleted in 13C in the NAD-ME compared with the NADP-ME grasses. However, Δ13C was not different between subtypes at high light, and, although Δ13C increased at low light, it did so similarly in both subtypes. This suggests that differences in leaf δ13C between the C4 subtypes are not caused by photosynthetic isotope fractionation and leaf δ13C is not a good indicator of bundle sheath leakiness. Additionally, low carbonic anhydrase (CA) in C4 grasses may influences Δ13C and should be considered when estimating the contribution of C4 grasses to the global isotopic signature of atmospheric CO2. It was found that measured Δ18O values were lower than those predicted from leaf CA activities and Δ18O was similar in all species measured. The Δ18O in these C4 grasses is similar to low Δ18O previously measured in C4 dicots which contain 2.5 times the leaf CA activity, suggesting that leaf CA activity is not a predictor of Δ18O in C4 plants.
机译：监测光合作用同位素交换是预测植物群落对全球碳循环响应气候变化影响的重要工具。 C 4 草在全球碳循环中起着重要作用，但它们对大气CO 2 同位素组成的贡献尚不十分清楚。瞬时测量 13 CO 2 （Δ 13 C）和C 18 OO（Δ 18 <在五个NAD-ME和七个NADP-ME C 4 草中进行了/ sup> O）同位素交换，以研究这些亚组中光合CO 2 同位素分馏的差异。如先前报道，与NADP-ME草相比，NAD-ME中叶片物质（δ 13 C）的同位素组成在 13 C中被耗尽。但是，亚型在强光下Δ 13 C并没有差异，尽管在弱光下Δ 13 C升高，但在两种亚型中相似。这表明C 4 亚型之间叶片δ 13 C的差异不是由光合同位素分馏引起的，叶片δ 13 C并非由光合同位素分馏引起。束鞘渗漏的良好指示。此外，C 4 草中的低碳酸酐酶（CA）可能会影响Δ 13 C，在估算C 4 草的贡献时应考虑大气CO 2 的全球同位素特征结果发现，测得的Δ 18 O值低于根据叶片CA活性预测的值，并且在所有被测物种中Δ 18 O均相似。这些C 4 草中的Δ 18 O与先前在C 4 双子叶植物中测得的低Δ 18 O相似叶片CA活性是叶片CA活性的2.5倍，表明叶片CA活性不是C 4 植物中Δ 18 O的预测因子。

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    《Journal of Experimental Botany》 |2008年第7期|p.1695-1703|共9页
  • 作者

    Asaph B. Cousins12* Murray R. Badger12 and Susanne von Caemmerer1;

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    1Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory, 2601 Australia 2ARC CoE, Plant Energy Biology, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory, 2601 Australia;

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