Physiological responses of annual bluegrass and creeping bentgrass to contrasted levels of O2 and CO2 at low temperatures
Ice encasement and impermeable winter protective covers can induce anaerobic conditions on golf greens. We assessed plant survival and biochemical changes of annual bluegrass (Poa annua L.) and creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.)] exposed to combinations of O2 and CO2 concentrations at low temperatures (1°C or –2°C). Results indicate that lack of O2 (anoxia) rather than high CO2 is the source of plant damage. However, combination of low O2 and high CO2 induced more severe damage than low O2 alone. Annual bluegrass was found to be more sensitive to anoxia than creeping bentgrass, and subfreezing temperature delayed anoxia-induced damage. Sucrose was depleted more rapidly under low O2 than under normal conditions. Fructan reserves were similarly mobilized in all treatments except for a more pronounced decline in annual bluegrass maintained under high CO2 at 1°C. A marked accumulation of asparagine at 1°C under normal atmospheric conditions did not occur under anoxia. Reversely, concentrations of alanine and tyrosine increased under low O2. Proline accumulation in plants incubated at –2°C was higher under low than under high CO2 treatments. We observed a relationship between the presence of volatile fatty acids and plant damage under low O2. Our study illustrates the complex interaction between O2 and CO2 that have both synergistic and independent effect on plant damage under anoxia at low temperatures.