Maximum leaf conductance driven by CO2 effects on stomatal size and density over geologic time
Maximum leaf conductance driven by CO2 effects on stomatal size and density over geologic time
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DOI：
10.1073/pnas.0904209106
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发表时间：
2009-06-23
影响因子：
11.1
通讯作者：
Beerling, David J.
中科院分区：
文献类型：
--
作者：
Franks, Peter J.;Beerling, David J.
气孔是叶片表皮上的微观结构，由两个特殊的保卫细胞形成，控制植物与大气之间的水蒸气和CO2交换。气孔大小（S）和密度（D）决定了CO2的最大叶片扩散（气孔）导度（g（cmax））同化的网站。虽然在化石记录中观察到的D的巨大变化与大气CO2相关，但S的类似巨大变化的重要意义却被忽视了。在这里，我们使用物理扩散理论来解释为什么在过去的4亿年中，S的巨大变化必然伴随着D和大气CO2的变化。特别是，我们表明，高密度的小气孔是唯一的途径，以达到最高的g（cmax）值所需的反CO2“饥饿”在低大气CO2浓度。这解释了循环的增加D和减少S明显的化石史下的二氧化碳贫大气的石炭二叠纪和新生代冰川的气孔。在大气CO2浓度上升的情况下，这种模式发生了逆转。小S的选择是至关重要的，以达到高g（cmax）下降的大气CO2下，因此，可能代表一种机制，连接CO2和增加气体交换能力的陆地植物在地质时期。
Stomatal pores are microscopic structures on the epidermis of leaves formed by 2 specialized guard cells that control the exchange of water vapor and CO2 between plants and the atmosphere. Stomatal size (S) and density (D) determine maximum leaf diffusive (stomatal) conductance of CO2 (g(cmax)) to sites of assimilation. Although large variations in D observed in the fossil record have been correlated with atmospheric CO2, the crucial significance of similarly large variations in S has been overlooked. Here, we use physical diffusion theory to explain why large changes in S necessarily accompanied the changes in D and atmospheric CO2 over the last 400 million years. In particular, we show that high densities of small stomata are the only way to attain the highest g(cmax) values required to counter CO2 "starvation'' at low atmospheric CO2 concentrations. This explains cycles of increasing D and decreasing S evident in the fossil history of stomata under the CO2 impoverished atmospheres of the Permo-Carboniferous and Cenozoic glaciations. The pattern was reversed under rising atmospheric CO2 regimes. Selection for small S was crucial for attaining high g(cmax) under falling atmospheric CO2 and, therefore, may represent a mechanism linking CO2 and the increasing gas-exchange capacity of land plants over geologic time.