DYNAMIC ANALYSIS OF MOISTURE STRESS IN TALL FESCUE (FESTUCA ARUNDINACEA) USING CANOPY TEMPERATURE, IRRADIATION, AND VAPOR DEFICIT

Dynamic canopy temperature and transpiration rates of tall fescue (festuca arundinacea) were studied under well-watered and moisture stress conditions, using step increase and decrease levels of irradiance. These studies were performed in a high irradiance plant growth chamber under controlled conditions. The fescue canopy was modeled using Laplace transfer functions, with plant temperature, irradiance, and vapor pressure deficit as input variables. Well-watered plants tended to respond as a second-order model, with a critically damped response for most levels of step irradiance inputs. Moderately stressed plants approached critical and under-damped response conditions. Severely stressed plants tended to respond closely to a first order model. The results illustrate the complex nature of plant feedback mechanisms as the plant anticipates moisture stress conditions.