Measurement of three-dimensional structure of plants with a simple device and estimation of light capture of individual leaves

Abstract

1. A simple device called a 'pocometer' (POlar COordinate METER) was developed to measure three-dimensional structure of plants. It consists of a tape-measure to measure distance and two protractors to measure zenith angle and azimuth angle. 2. The pocometer can determine locations of points within a few metres distance with a resolution of less than 1 cm. Location of any point on a plant can be measured in 10 to 30 s depending on the ease of pulling the tape measure to the point of interest. 3. A system to use data obtained with the pocometer to calculate plant light capture was developed. The degree of shading at any point on a plant is estimated by checking obstruction by other plant parts of the view toward the sky at that point. 4. Photon flux density (PFD) on leaf surfaces was estimated for Aucuba japonica, a broad-leaved evergreen shrub, using the above system. The estimated PFDs for individual leaves of a plant corresponded to the sensor-measured PFDs with correlation coefficients of 0.67 to 0.92.