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

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.

Differential biomass and nutrient accumulation in perennial ryegrass accessions under excess water treatment in field conditions during winter

“…Substantial variation among accessions in response to flooding suggests that in the future, breeding may play an important role to improve the resilience of perennial ryegrass to flooding. Holohan et al (2019) showed an improvement in ecological adaptation of grassland species by selection in just a few generations. Detailed ecophysiological studies are necessary to determine the optimal water saturation of soil types for perennial ryegrass and the point in the physiology of the species from where excess water will be detrimental.…”

Biological Flora of Britain and Ireland:Geranium pratense

“…The measurements in these natural habitats demonstrated a negative response of this mesophytic species to environmental stress in the dry and hot steppe habitat (Iljin, 1916). Holohan et al (2019) measured leaf gas exchange in G. pratense grown in a free‐air carbon dioxide enrichment (FACE) field experiment in a floodplain meadow near Giessen in Germany (Jäger et al, 2003). Plants grown at ambient (400 ppm) and elevated (480 ppm) levels of CO 2 for 17 years reacted differently to the experimental step increase in CO 2 concentration from 200 to 2000 ppm.…”

“…This unique physiological response was persistent among offspring and was irreversible in at least a single generation even when returned to growth at 400 ppm [CO 2 ] in growth chambers. However, the ability to increase WUEi does not necessarily translate into an ecological advantage for the species (Holohan et al, 2019).…”