Effects of Different Leaf Position on Leaf Color Measurements for a Soybean Community and Advantages of Transmitted Light Utilization

Abstract

This study investigated error factors of leaf color measurement attributable to the soybean community structure and the direction of illuminant. Results of SPAD value measurements of individual leaves in different leaf positions clarified that those of leaves in lower positions differ from those of leaves in upper positions. The average SPAD value of the upper three leaves is useful as a representative value of the community. Results of measuring the multidirectional spectrum properties of reflected and transmitted light from an individual soybean leaf show that, compared to using reflected light, measuring with transmitted light decreases measurement error attributable to incident angles.