Department of Biology, San Francisco State University, San Francisco, California, United States of America.
School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, United States of America.
PLoS Biol. 2018 Jan 11;16(1):e2003706. doi: 10.1371/journal.pbio.2003706. eCollection 2018 Jan.
The abrupt origin and rapid diversification of the flowering plants during the Cretaceous has long been considered an "abominable mystery." While the cause of their high diversity has been attributed largely to coevolution with pollinators and herbivores, their ability to outcompete the previously dominant ferns and gymnosperms has been the subject of many hypotheses. Common among these is that the angiosperms alone developed leaves with smaller, more numerous stomata and more highly branching venation networks that enable higher rates of transpiration, photosynthesis, and growth. Yet, how angiosperms pack their leaves with smaller, more abundant stomata and more veins is unknown but linked-we show-to simple biophysical constraints on cell size. Only angiosperm lineages underwent rapid genome downsizing during the early Cretaceous period, which facilitated the reductions in cell size necessary to pack more veins and stomata into their leaves, effectively bringing actual primary productivity closer to its maximum potential. Thus, the angiosperms' heightened competitive abilities are due in no small part to genome downsizing.
在白垩纪，开花植物的突然起源和快速多样化长期以来一直被认为是一个“可恶的谜”。虽然它们的多样性很大程度上归因于与传粉者和食草动物的共同进化，但它们能够胜过以前占主导地位的蕨类植物和裸子植物的能力一直是许多假说的主题。其中常见的一种观点是，被子植物独自进化出了具有更小、更多数量的气孔和更分支的叶脉网络的叶子，从而能够实现更高的蒸腾、光合作用和生长速率。然而，被子植物如何在叶子中排列更小、更丰富的气孔和更多的叶脉尚不清楚，但我们表明，这与细胞大小的简单生物物理限制有关。只有在白垩纪早期，被子植物谱系经历了快速的基因组缩小，这促进了细胞大小的减少，从而使更多的叶脉和气孔能够排列在叶子中，有效地使实际的初级生产力更接近其最大潜力。因此，被子植物更高的竞争能力在一定程度上归因于基因组缩小。
