Validating Temperature Sensors for a High-Throughput Automated Bud Break Sensor

In response to a growing need for high-throughput technology that increases our understanding of the genomic basis of bud break, we are developing and validating a sensor for attaching to trees. This sensor features fiber optic cables that sense bud expansion and day length, and an integrated-circuit digital thermometer for measuring temperature at the bud site. Because our sensors are exposed to solar radiation, wind, precipitation, and more, their measurements integrate environmental variables into one value. To better understand what exactly our sensor’s digital thermometers were measuring relative to air and foliar temperature, we instrumented a small tree with a thermal infrared camera, type-T thermocouples, an aspirated thermal hygrometer, and our sensors. Data was collected for fourteen days in the springtime, with measurements being recorded every fifteen minutes. Our preliminary results indicate that our sensors’ digital thermometers are a better measure of foliar temperature than standard type-T thermocouples, and tend to measure values between air and foliar temperatures. Daytime measurements differed less than 2˚C from air temperature and less than 1˚C from foliar temperature. Nighttime measurements differed less than 1˚C from air temperature and less than 3˚C from foliar temperature. Nighttime measurements also had much lower standard deviations than the thermocouples and thermal hygrometer, possibly due to an insulating effect from the clear water-proofing on our probes. These data are biologically significant, as they will inform the calculation of highly localized chilling and forcing units accrued by individual buds, allowing us to account for the environment when phenotyping plants.