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New Phytol. 2016 Jan;209(1):94-103. doi: 10.1111/nph.13579. Epub 2015 Jul 31.

Using modern plant trait relationships between observed and theoretical maximum stomatal conductance and vein density to examine patterns of plant macroevolution.

Author information

1
Earth Institute, O'Brien Centre for Science, University College Dublin, Belfield, Ireland.
2
School of Biology and Environmental Science, University College Dublin, Belfield, Ireland.
3
School of Biological Science, University of Essex, Colchester, CO4 3SQ, UK.

Abstract

Understanding the drivers of geological-scale patterns in plant macroevolution is limited by a hesitancy to use measurable traits of fossils to infer palaeoecophysiological function. Here, scaling relationships between morphological traits including maximum theoretical stomatal conductance (gmax ) and leaf vein density (Dv ) and physiological measurements including operational stomatal conductance (gop ), saturated (Asat ) and maximum (Amax ) assimilation rates were investigated for 18 extant taxa in order to improve understanding of angiosperm diversification in the Cretaceous. Our study demonstrated significant relationships between gop , gmax and Dv that together can be used to estimate gas exchange and the photosynthetic capacities of fossils. We showed that acquisition of high gmax in angiosperms conferred a competitive advantage over gymnosperms by increasing the dynamic range (plasticity) of their gas exchange and expanding their ecophysiological niche space. We suggest that species with a high gmax (> 1400 mmol m(-2) s(-1) ) would have been capable of maintaining a high Amax as the atmospheric CO2 declined through the Cretaceous, whereas gymnosperms with a low gmax would experience severe photosynthetic penalty. Expansion of the ecophysiological niche space in angiosperms, afforded by coordinated evolution of high gmax , Dv and increased plasticity in gop , adds further functional insights into the mechanisms driving angiosperm speciation.

KEYWORDS:

evolution of angiosperms; functional traits; maximum theoretical stomatal conductance (gmax); palaeophysiology; plasticity; stomatal density; stomatal evolution; vein density (Dv)

PMID:
26230251
PMCID:
PMC5014202
DOI:
10.1111/nph.13579
[Indexed for MEDLINE]
Free PMC Article

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