Growth and Physiological Responses of Creeping Bentgrass (Agrostis stolonifera L.) to Elevated Carbon Dioxide Concentrations.

Atmospheric CO₂ levels are predicted to double over the next century and research to date has focused mainly on effects to harvest yield only in agronomic crops.  Little work has been performed investigating effects on vegetative growth of cultivated perennial grass species such as turfgrass. The objective of this study was to investigate effects of doubling ambient CO₂ on growth and physiological activities in a widely-utilized turfgrass species, creeping bentgrass (Agrostis stolonifera L. ‘Penncross’).   Plants were established in fritted clay medium and maintained under controlled-climate, well-irrigated conditions.  Mature plants were trimmed to identical heights and placed in closed-top growth chambers set to 23.5/18.0 °C (day/night), 50% relative humidity, 800 µmol m^-1s^-1 (PAR), and either ambient (400±10 ppm) or elevated (800±10 ppm) CO₂ levels for twelve weeks.  Turfgrass grown under elevated CO₂ displayed dramatic morphological changes compared to ambient controls including significant increases in stolon length (faster growth rate), stomatal density, and net weight of shoots and leaves.  Elevated CO₂ caused a reduction in specific leaf area, leaf chlorophyll content, and total nonstructural carbohydrate content in shoots, while net root weight increased slightly and root-to-shoot ratio was unaffected.  Increased rates of lateral spread and decreased rates of leaf vertical elongation are highly desirable traits in the turfgrass industry.  Results from this study provide a basis for further investigation of mechanisms underlying changes in morphology and carbohydrate content in turfgrass plants responding to increased CO₂ levels and will also facilitate research into CO₂ interactions with abiotic stress such as drought and heat.