Influence of mowing frequency and mower sharpness on efficiency of PSII and antioxidant and carbohydrate metabolism of creeping bentgrass

Sports fields are mown primarily to provide a uniform surface for ball roll and bounce. However, mowing creates openings that facilitate water loss and entry points for pathogens, and increases susceptibility to other stresses. The objectives of our research were to identify physiological mechanisms that allow creeping bentgrass to tolerate close and frequent mowing. Plants often increase formation of reactive oxygen species (ROS) in response to wounding. Accumulation of ROS may damage macromolecules such as lipids, proteins, and nucleic acids. Damage to these macromolecules may result in reduced plant growth and vigor, or even death. Plants form enzymes to quench ROS and protect cells from oxidative damage. However, activities of ROS-scavenging enzymes often are reduced during stress. In our research, activities of the ROS-quenching enzymes catalase and ascorbate peroxidase were reduced in mowed grasses. Reduced activities of these enzymes may result in accumulation of ROS. However, no differences were observed in levels of lipid peroxidation between not-cut and mowed grasses, indicating that accumulation of ROS was not sufficient to cause severe oxidative stress. Although toxic at high concentrations, ROS may act as a component of a signal transduction pathway that acclimates not-stressed tissue to potential stress. It is necessary for grasses to regrow leaf tissue removed by mowing. Reserve carbohydrates often are hydrolyzed to generate carbon for respiration and to provide substrates for development of leaf and shoot tissue. Creeping bentgrass forms fructans as reserve carbohydrates. In our research, fructans were reduced in mown grasses compared to not-cut grasses. Glucose levels also were reduced in mowed grasses compared to not-cut grasses. Glucose likely was oxidized in the glycolytic pathway and respiration to provide energy for formation of new leaf tissue. It is important to remember that mowing is a stress and that mowing programs should balance agronomic requirements of grasses with sports play demands in order to produce uniform and visually appealing turf that is vigorous in growth.