Heritable Changes in Physiological Gas Exchange Traits in Response to Long-Term, Moderate Free-Air Carbon Dioxide Enrichment.

Aidan David Holohan,Christoph Müller,Jennifer Mcelwain

doi:10.3389/fpls.2019.01210

Abstract

Atmospheric carbon dioxide ([CO2]) concentrations significantly alter developmental plant traits with potentially far-reaching consequences for ecosystem function and productivity. However, contemporary evolutionary responses among extant plant species that coincide with modern, anthropogenically driven [CO2] rise have rarely been demonstrated among field-grown plant populations. Here we present findings from a long-term, free-air carbon dioxide enrichment (FACE) study in a seminatural European grassland ecosystem in which we observe a differential capacity among plant species to acclimate intrinsic water-use efficiencies (WUEs) in response to prolonged multigenerational exposure to elevated [CO2] concentrations. In a reciprocal swap trial, using controlled environment growth chambers, we germinated seeds from six of the most dominant plant species at the FACE site [Arrhenatherum elatius (L.), Trisetum flavescens (L.), Holcus lanatus (L.), Geranium pratense (L.), Sanguisorba officinalis (L.), and Plantago lanceolata (L.)]. We found that long-term exposure to elevated [CO2] strongly influenced the dynamic control of WUEi in the first filial generations (F1) of all species as well as an unequal ability to adapt to changes in the [CO2] of the growth environment among those species. Furthermore, despite trait–environment relationships of this nature often being considered evidence for local adaptation in plants, we demonstrate that the ability to increase WUEi does not necessarily translate to an ecological advantage in diverse species mixtures.

Highlights

Processes that govern guard cell responses to environmental stimuli and the anatomical, morphological, and physiological responses that are driven by both biotic and abiotic pressures have significant implications for interpreting plant–atmosphere interactions (Franks et al, 2012; Franks et al, 2017)
Model fit parameters (AIC and R2 values) demonstrated that free-air carbon dioxide enrichment (FACE) treatment was a better predictor of dynamic WUEi response than chamber treatment for both A. elatius and T. flavescens, whereas for all other species, chamber treatment was the more significant factor
Of the six species included in this study, growth under elevated [CO2] at the Giessen FACE site resulted in an enhanced capacity to increase WUEi as [CO2] increased from 200 to 2,000 ppm (Figure 1)

Summary

Introduction

Processes that govern guard cell responses to environmental stimuli and the anatomical, morphological, and physiological responses that are driven by both biotic and abiotic pressures have significant implications for interpreting plant–atmosphere interactions (Franks et al, 2012; Franks et al, 2017). Growth at elevated [CO2] concentrations has often been shown to provoke morphological (McElwain and Chaloner, 1995; Royer, 2001; Woodward and Kelly, 1995) and physiological (Drake et al, 1997; Ainsworth and Long, 2005) stomatal acclimation responses, which limit water loss, maximize carbon acquisition, increase photosynthetic rate, and increase water-use efficiencies (WUEs) through increasing diffusional resistance (Ainsworth and Rogers, 2007). Acclimation responses to increased [CO2], those associated with leaf gas exchange rates, have been demonstrated in numerous studies and are typically the result of long-term exposure to elevated [CO2], often resulting in alterations to resource allocation patterns that directly influence leaf photosynthetic and gas exchange rates (Anderson et al, 2001; Chen, 2005; Lee et al, 2011; Rogers and Ellsworth, 2002). Despite the large number of studies that have described acclimation responses to elevated [CO2], there are some studies that demonstrate no such response (Bader et al, 2010; Crous et al, 2011; Herrick and Thomas, 2001; Leakey et al, 2006; Usuda, 2006), and there may exist a differential acclimation capacity to increasing [CO2] among modern plant species

Methods

Results

Discussion

Conclusion