Cytotype-level responses and of Spartina plants to drought and elevated atmospheric CO₂ concentration

Global change factors, such as drought and elevated atmospheric CO₂ levels, can have strong impacts on plant performance and evolutionary development. We investigated responses of Spartina (syn.: Sporobolus P.M.Peterson & Saarela) plants on different ploidy levels (cytotypes), i.e., the hybrid Spartina x townsendii H. Groves & J. Groves (syn.: Sporobolus × townsendii P.M.Peterson & Saarela) and its genome-duplicated (allopolyploid) descendant Spartina anglica C.E. Hubbard (syn.: Sporobolus anglicus P.M.Peterson & Saarela), to drought and elevated atmospheric CO₂ levels, regarding plant functional traits and biomass. Spartina plants were sampled in 2017 from a Spartina-marsh at Sönke-Nissen-Koog, Germany, and cytotype analysis was performed by DAPI staining for flow cytometry. Ramets from donor individuals of these plants were used in a greenhouse experiment at University of Hamburg, Germany. The plants were grown in 2 L pots and weekly fertilized with commercial Hakaphos® Blau (15-10-15) NPK fertilizer solution (1% v/v; 50 mL per pot). Three cytotype replicates of both hybrid and allopolyploid plants were treated from May to October 2018 under greenhouse daylight conditions (day/night air temperature 27 °C / 22 °C; 70%–80% relative air humidity; length of the photoperiod typical for the northern Germany region) with drought (vs. well-watered) and elevated (vs. ambient) CO₂ concentrations. At the end of the experiment, total biomass and plant traits, i.e., root-to-shoot ratio, stem diameter, leaf area, stem density, and stomatal length were determined. We here report the result values of three to six technical replicates from three biological replicates per treatment combination.