Infrared Temperature Measurements: Application in Field-Based Phenotyping.

Measurements of plant canopy temperature with infrared radiometers have been used for decades to indicate plant water use and water status. Canopy temperature is related to plant water use and status through stomata. As stomata open and close in response to changing soil and atmospheric conditions, transpiration (cooling) varies, thereby influencing canopy temperature. In recent years, infrared radiometers and thermal imagers have been mounted on stationary and mobile measurement platforms used for field-based phenotyping of crop plants. Challenges of making plant temperature measurements, including radiometer field of view, response time, and accuracy, are discussed. Use of plant temperature data to estimate plant water use and water status is also discussed, and demonstrated with measurements from a stationary platform in a cropped field and a mobile platform moving along a crop row. Stationary measurements allow for continuous monitoring of canopy water status and can reveal daily and seasonal patterns for the canopy. Mobile measurements allow for monitoring of multiple trials over a short time interval and comparison of trials.