Rapid Data Acquisition for In-Field Plant Phenomics.

High throughput sensing is necessary for the rapid acquisition of plant canopy physical and physiological parameters on field scales. Simultaneous measures of these descriptive parameters will provide a clearer picture of plant response to biotic and abiotic stressors. Information obtained can assist in early identification of desired genetic traits and the degree to which they are expressed. Identifying these traits and their expression can provide higher efficiency in genetic selection for breeding programs and define better management practices for genetics currently on the market. To meet this sensing need, a new multi-parameter sensor system was developed, and accordingly, represents a new integrated approach for measuring radiative transfer and physiological characteristics of plant canopies. The phenomics system was developed and provided by Holland Scientific (Lincoln, NE, USA) and was field tested on winter wheat during the spring growing season of 2013. The system is a combination of active and passive sensors consisting of a three-band active optical sensor (AOS), a multi-parameter data acquisition sensor and geospatial data logger (Holland Scientific GeoSCOUT GLS-400). The AOS (Holland Scientific Crop Circle ACS-430P) provides measurements for red, red-edge (RE) and near infrared (NIR) reflectance, red and red-edge normalized difference vegetation indices (NDVI and NDRE)  and estimation models for leaf area index (LAI), plant canopy chlorophyll content (CCC) and optical sensor-to-plant distance. The multi-parameter sensor (Holland Scientific Crop Circle DAS43X) provides measurements for passive upwelling and downwelling photosynthetic active radiation (PAR), passive temperature for both canopy and ambient air, humidity and atmospheric pressure. Canopy data was collected at a rate of 5 samples per second and geo-referenced using a Trimble RTK GPS receiver. From this dual sensor data we were able to derive CCC, LAI, canopy height, canopy temperature departure (ΔT), and fractionally absorbed PAR (fAPAR). Data was collected at three dates on a yield trial study that includes thirteen public varieties adapted for the Great Plains and grown in Eastern Nebraska. We were able to characterize the highest yielding variety as a shorter plant with high LAI, CCC and fAPAR. Potentially, a variety with a higher light use efficiency (LUE) throughout the canopy, most likely a result of an erectophyle structure of the leaves. This particular variety had the highest ΔT in the presence of acute heat stress, indicating increased rates of transpiration as a strategy of heat tolerance. The system has demonstrated that significant discrimination can be obtained for a variety of plant canopy physical and physiological parameters in a high throughput manner using the set of measurements provided by the sensor suite.