Effects of elevated carbon dioxide on drought tolerance and post‐drought recovery involving rhizome growth in Kentucky bluegrass.

Drought tolerance and rapid post‐stress recovery are critical survival strategies for turfgrass management in areas with limited rainfall and irrigation. This study sought to determine whether elevated CO2 could improve drought tolerance in rhizomatous Kentucky bluegrass (Poa pratensis L.) by protecting rhizomes from stress damage and promote regrowth and regeneration of daughter plants from rhizomes upon rewatering. Plants (cv. 'Baron') were grown at elevated CO2 concentration (800 μl L−1) or ambient CO2 concentration (400 μl L−1) for 28 d and then exposed to well‐irrigated conditions (control) or drought stress by withholding irrigation for an additional 28 d, followed by rewatering in growth chambers. Elevated CO2–treated plants had significantly higher leaf relative water content, visual quality, and membrane stability during drought compared with ambient CO2–treated plants. Rhizome nodes of elevated CO2–treated plants maintained significantly higher viability and lower content of abscisic acid and auxin under drought stress. In response to rewatering, plants previously exposed to drought stress under elevated CO2 exhibited increased growth of new shoots measured as total shoot biomass and daughter‐plant biomass, and an increased number of rhizomes, as well as greater canopy density compared with plants at ambient CO2. This study suggested that elevated CO2 concentration was able to protect rhizomes from drought damage and reactivate rhizomes for regeneration of new plants when drought was relieved by irrigation. [ABSTRACT FROM AUTHOR]