Month: September 2022

WHOPPING INCREASE IN STOMATA DENSITIES. "By the time large laminate leaves became widespread in late Devonian/early Carboniferous fossil floras, the concentration of atmospheric CO2 had fallen, and stomatal densities had increased by up to a 100 times the value of early vascular land plant axes." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

PROBLEM SOLVED. "Large leaves of late Devonian/ early Carboniferous plants attained transpiration rates sufficiently high to maintain temperatures well below the lethal threshold, despite intercepting more solar energy." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

PRIMARY KNOCK-ON EFFECTS. "But in the late Palaeozoic, the evolution of large leaves required the co-evolution of the root and vascular systems for improved water delivery and transport to sustain higher transpiration rates." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

SECONDARY EFFECTS. "Deeper roots accessed water and nutrients from a greater volume of soil, whilst xylem conduit enlargement and the appearance of secondary growth of xylem by the end of the Devonian increased the hydraulic conductance through stems and trunks to the leafy canopy, helping to maintain higher transpiration rates." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

EXISTING MACHINERY. "Molecular genetics indicates that the developmental mechanisms required for leaf production in vascular plants were recruited long before the advent of large megaphylls. According to theory, this morphogenetic potential was only realized as the concentration of atmospheric CO2 declined during the late Palaeozoic." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

SINKING CARBON. "Surprisingly, plants effectively policed their own evolution since the decrease in CO2 was brought about as terrestrial floras evolved accelerating the rate of silicate rock weathering and enhancing sedimentary organic carbon burial, both of which are long-term sinks for CO2." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

PLANTS ACCELERATED ANIMAL EVOLUTION. "The recognition that plant evolution responds to and influences CO2 over millions of years reveals the existence of an intricate web of vegetation feedbacks regulating the long-term carbon cycle. Several of these feedbacks destabilized CO2 and climate during the late Palaeozoic but appear to have quickened the pace of terrestrial plant and animal evolution at that time." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

CONSERVED MERISTEM GENES. "Leaves in vascular plants are produced by determinate growth on the flanks of indeterminate shoot apical meristems. Inderminate growth of the shoot apical meristem is controlled by the knotted-like homeobox gene family (KNOX). KNOX genes are present in some green algae (e.g. Acetabularia), mosses, ferns, gymnosperms and angiosperms and their function may be highly conserved." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

KNOWING UP FROM DOWN. "Leaf production also requires differentiation between adaxial (upper) and abaxial (lower) surfaces because the former is specialized for the efficient capture of solar energy and the latter for gas exchange." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn

THE UP INNOVATION. "Deriving from the apical vegetative meristem flank, the abaxial surface is as old as land plants themselves, so genes specifying adaxial identity constitute a key innovation in leaf evolution. Plants appear to have evolved a complex hierarchy of transcription factor activation and depression, with the HD-ZIP (homeodomain–leucine zipper) gene family promoting adaxial leaf surfaces and others promoting abaxial differentiation." http://aob.oxfordjournals.org/content/96/3/345.full.pdf View in LinkedIn