Leaf hydraulic evolution led a surge in leaf photosynthetic capacity during early angiosperm diversification

Abstract

Angiosperm evolution transformed global ecology, and much of this impact derives from the unrivalled vegetative productivity of dominant angiosperm clades. However, the origins of high photosynthetic capacity in angiosperms remain unknown. In this study, we describe the steep trajectory of leaf vein density (D(v)) evolution in angiosperms, and predict that this leaf plumbing innovation enabled a major shift in the capacity of leaves to assimilate CO(2). Reconstructing leaf vein evolution from an examination of 504 angiosperm species we found a rapid three- to fourfold increase in D(v) occurred during the early evolution of angiosperms. We demonstrate how this major shift in leaf vein architecture potentially allowed the maximum photosynthetic capacity in angiosperms to rise above competing groups 140-100 Ma. Our data suggest that early terrestrial angiosperms produced leaves with low photosynthetic rates, but that subsequent angiosperm success is linked to a surge in photosynthetic capacity during their early diversification.

Conductancia hidráulica foliar y vulnerabilidad a la cavitación disminuyen con la altitud en Phacelia secunda J.F. Gmel. (Boraginaceae)

“…Sin embargo, la menor Kf también se correlaciona con menores tasas de conductancia estomática y de asimilación de carbono, por lo cual las plantas que ven disminuida su Kf ven reducida directamente sus tasas fotosintéticas (Nardini et al 2008, Hubbard et al 2001, Resco et al 2008, Brodribb & Field 2010. Esto podría llegar a ser una limitante en la respuesta fotosintética de estas plantas al incremento en la temperatura proyectada por el cambio climático.…”

Evolution of C 4 plants: a new hypothesis for an interaction of CO 2 and water relations mediated by plant hydraulics

“…Previous studies of adaptation to these conditions within species or across closely related species within given lineages have shown increased vein densities, and thus shorter interveinal distances [76][77][78][79]. This higher vein density would permit greater g s and higher A during periods with high water availability, to compensate for low CO 2 .…”

An exceptional role for flowering plant physiology in the expansion of tropical rainforests and biodiversity

“…Because water loss is an inevitable component of leaf gas exchange, photosynthesis is limited by the ability of the plant to replace water lost through transpiration. Since the path length from vein to stomata is an important determinant of leaf hydraulic conductivity, both CO 2 assimilation and water transpirational loss are tightly correlated with the density of veins within the leaf (Brodribb et al 2007;Boyce et al 2009;Brodribb & Feild 2010;McKown et al 2010). Vein density, therefore, provides a physiological proxy measurable in the fossil record and allows assessment of long extinct taxa with physiologies previously unconstrained.…”