Estimating canopy light interception and absorption using leaf mass per unit leaf area in Solanum melongena

Knowledge of canopy light interception and absorption is fundamental for understanding many aspects of crop growth and productivity, and for crop modelling. Light interception is commonly measured with expensive equipment or estimated with elaborate models; simpler and more economical ways of estimation would be advantageous. Since leaf mass per unit leaf area (M(A)) is closely related to long-term light interception by leaves, the latter can be estimated by measuring M(A). In this study, partitioning of leaf area into one of six classes of M(A) was used to estimate canopy light interception and absorption in aubergine (Solanum melongena L.) grown with different amounts of nitrogen fertilizer and with or without artificial shade. Although plants grown with ample fertilizer had a greater leaf area index (LAI) than those grown with less nitrogen, the increase in leaf area occurred in the lower and intermediate M(A) classes, while the leaf area in the two highest M(A) classes was similar. Artificially shaded plants had more leaf area in the lower M(A) classes and less in the higher classes compared to unshaded plants, showing acclimation to low light conditions. The amount of light intercepted daily by leaves in each M(A) class was estimated using the previously determined light: M(A) relationship. Canopy light interception was calculated as the sum of intercepted light for all M(A) classes, and canopy light absorption was estimated from light interception data assuming a constant absorption coefficient (82%). To validate the results, the estimated values were compared to those calculated from independent measurements of light absorption carried out in the same field. Results indicate that it is possible to estimate canopy light interception and absorption from the partitioning of leaf area into M(A) classes.