Litters of photosynthetically divergent grasses exhibit differential metabolic responses to warming and elevated CO₂

Authors

Vidya Suseela, Clemson University
Daniella Triebwasser-Freese, Clemson University
Nora Linscheid, Rheinische Friedrich-Wilhelms-University Bonn
Jack A. Morgan, USDA-ARS
Nishanth Tharayil, Clemson University

Date of this Version

2014

Citation

ECOSPHERE www.esajournals.org, Volume 5(8), Article 0, 2014

Comments

Copyright 2014 Suseela et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License

Abstract

Climatic stress such as warming would alter physiological pathways in plants leading to changes in tissue chemistry. Elevated CO₂ could partly mitigate warming induced moisture stress, and the degree of this mitigation may vary with plant functional types. We studied the composition of structural and non-structural metabolites in senesced tissues of Bouteloua gracilis (C4) and Pascopyrum smithii (C3) at the Prairie Heating and CO₂ Enrichment experiment, Wyoming, USA. We hypothesized that P. smithii and B. gracilis would respond to unfavorable global change factors by producing structural metabolites and osmoregulatory compounds that are necessary to combat stress. However, due to the inherent variation in the tolerance of their photosynthetic pathways to warming and CO₂, we hypothesized that these species will exhibit differential response under different combinations of warming and CO₂ conditions. Due to a lower thermo-tolerance of the C4 photosynthesis we expected B. gracilis to exhibit a greater metabolic response under warming with ambient CO₂ (cT) and P. smithii to exhibit a similar response under warming combined with elevated CO₂ (CT). Our hypothesis was supported by the differential response of structural compounds in these two species, where cT increased the content of lignin and cuticular-matrix in B. gracilis. In P. smithii a similar response was observed in plants exposed to CT, possibly due to the partial alleviation of moisture stress.With warming, the total cell-wall bound phenolic acids that cross link polysaccharides to lignins increased in B. gracilis and decreased in P. smithii, indicating a potentially adaptive response of C4 pathway to warming alone. Similarly, in B. gracilis, extractable polar metabolites such as sugars and phenolic acids increased with the main effect of warming. Conversely, in P. smithii, only sugars showed a higher abundance in plants exposed to warming treatments indicating that warming alone might be metabolically too disruptive for the C3 photosynthetic pathway. Here we show for the first time, that along with traditionally probed extractable metabolites, warming and elevated CO₂ differentially influence the structural metabolites in litters of photosynthetically divergent grass species. If these unique metabolite responses occur in other species of similar functional types, this could potentially alter carbon cycling in grasslands due to the varying degradability of these litters.