Physiological Responses of Creeping Bentgrass to Pigment‐Containing Products

Providing relief from summer stress is a constant goal when maintaining creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.)] golf putting greens. Colorants and other pigment‐containing products are marketed as a means of relieving summer stress but research supporting such claims is limited and was the objective of this study. Pigment‐containing products evaluated on bentgrass maintained under supraoptimal (>30°C) temperature stress included: TurfScreen (a combination of zinc oxide [ZnO], a green pigment, and titanium dioxide [TiO2]) and PAR (a commercial copper‐based pigment). Carbon dioxide exchange rate (µmol CO2 cm–2 s–1) was reduced >100% following Turfscreen and PAR applications and evapotranspiration rate (µmol H2O cm–2 s–1) was reduced ∼10% compared to nonstressed control plants. Fluorescence (Fv/Fm) was reduced ∼16% following Turfscreen and PAR application. Products (including a commercial paint and an additional copper‐based pigment, Foursome) were also applied to acrylic sheets to measure the transmission of photosynthetically active radiation. PAR and Foursome reduced the transmission of photosynthetically active radiation ∼20%, while TurfScreen and paint reduced it by 39 and 46%, respectively. Microscopy images revealed TurfScreen (higher viscosity) remained on the leaf surface, and covered stomata while PAR (lower viscosity) entered the leaf via stomata. Overall, products evaluated provided little consistent physiological benefit to creeping bentgrass in a heat‐stressed environment.