Cold Tolerance in Annual Bluegrass (Poa annua L.) Exposed to Anoxic and Hypoxic Conditions

The use of impermeable tarps has been adopted by golf course superintendents in North America to prevent winter injury due to direct cold temperature exposure and ice damage; however, without ventilation, anoxic conditions can develop under tarps, which can result in extensive damage to annual bluegrass (Poa annua L.) greens. Currently, no information is available to help superintendents determine when or how frequently ventilation under tarps or ice cover is needed for injury prevention. A controlled environment study was performed to determine the effects of anoxic and hypoxic conditions on cold tolerance, represented by the lowest temperature at which 50% survival occurs and nonstructural carbohydrate concentrations of annual bluegrass, and to determine at what gas concentrations managers should ventilate under impermeable tarps. In general, turf exposed to anoxic conditions had reduced cold tolerance at all sampling days, highlighting the importance of avoiding anoxic conditions under impermeable covers. Glucose, fructose, sucrose, and total sugar concentrations did not respond to atmospheric gas treatments as predicted, and no relationship between elevated carbohydrates and increased cold tolerance was observed in this study. Conflicting reports on the role of carbohydrates in winter hardiness suggest a more biologically complex relationship between the two factors, and other factors such as proteins and phytotoxic compounds should be investigated. It is recommended that superintendents who are monitoring atmospheric conditions under impermeable tarping systems should ventilate under tarps as soon as oxygen levels reach 5% to prevent winter injury.