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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Leaf fossil record suggests limited influence of atmospheric CO_2 on terrestrial productivity prior to angiosperm evolution
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Leaf fossil record suggests limited influence of atmospheric CO_2 on terrestrial productivity prior to angiosperm evolution

机译：叶片化石记录表明，在被子植物进化之前，大气中CO_2对陆地生产力的影响有限

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Declining CO_2 over the Cretaceous has been suggested as an evolutionary driver of the high leaf vein densities (7-28 mm mm~(-2)) that are unique to the angiosperms throughout all of Earth history. Photosynthetic modeling indicated the link between high vein density and productivity documented in the modern low-CO_2 regime would be lost as CO_2 concentrations increased but also implied that plants with very low vein densities (less than 3 mm mm~(-2)) should experience substantial disadvantages with high CO_2. Thus, the hypothesized relationship between CO_2 and plant evolution can be tested through analysis of the concurrent histories of alternative lineages, because an extrinsic driver like atmospheric CO_2 should affect all plants and not just the flowering plants. No such relationship is seen. Regardless of CO_2 concentrations, low vein densities are equally common among nonangio-sperms throughout history and common enough to include forest canopies and not just obligate shade species that will always be of limited productivity. Modeling results can be reconciled with the fossil record if maximum assimilation rates of nonflow-ering plants are capped well below those of flowering plants, capturing biochemical and physiological differences that would be consistent with extant plants but previously unrecognized in the fossil record. Although previous photosynthetic modeling suggested that productivity would double or triple with each Phaner-ozoic transition from low to high CO_2, productivity changes are likely to have been limited before a substantial increase accompanying the evolution of flowering plants.
机译：已经提出白垩纪CO_2的下降是整个地球历史上被子植物特有的高叶静脉密度（7-28mm mm〜（-2））的进化驱动力。光合作用模型表明，随着CO_2浓度的增加，现代低CO_2方案中记录的高脉密度与生产力之间的联系将消失，但也暗示具有极低静脉密度（小于3 mm mm〜（-2））的植物应经历高CO_2的严重缺点。因此，可以通过分析替代谱系的同时历史来检验CO_2与植物进化之间的假设关系，因为像大气CO_2这样的外部驱动因素应该影响所有植物，而不仅是开花植物。没有这样的关系。不论CO_2的浓度如何，低静脉密度在整个历史上在非血管精子中都同样普遍，并且足以覆盖森林冠层，而不仅仅是专为生产力有限的阴影物种。如果不引流植物的最大同化率的上限远低于开花植物，则建模结果可以与化石记录相一致，从而捕获与现存植物一致但以前在化石记录中未发现的生化和生理差异。尽管以前的光合作用模型表明，从低到高CO_2的每个Phaner-生代转换，生产力都会翻一番或三倍，但生产力的变化可能会受到限制，然后随着开花植物的进化而大幅提高。

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