Simple assessment of needleleaf and broadleaf chlorophyll content using a flatbed color scanner

Abstract

Total chlorophyll a and b content (Chlab) of leaves is an important indicator of the photosynthetic capacity, nutritional condition, and health status of plants. Developing low-cost, easily accessible methods for estimating foliar Chlabof needleleaf species would enable a broad range of forestry applications. We evaluated data acquired using an off-the-shelf flatbed color scanner to assess its utility in quantifying needleleaf Chlab. Red and green digital numbers (DN) of the scan image were obtained from needle leaves of oneseed juniper ( Juniperus monosperma (Engelm.) Sarg.) and piñon pine ( Pinus edulis Engelm.) in addition to two broadleaf species for comparison purposes. Values of laboratory-determined Chlab(range 1.5–64.0 µg·cm–2) were then predicted using the DN values from the scanner-imaged needle leaves as a regression estimator. The red or green DN values of the scanner-imaged needle leaves were curvilinearly related to Chlabwith an r2of 0.67 (RMSE = 4.72 µg·cm–2, p < 0.001) for juniper needles and an r2of 0.54 (RMSE = 5.51 µg·cm–2, p < 0.001) for pine needles. Although our results suggest that flatbed scanner derived Chlabestimates are not suitable for applications where highly accurate Chlabestimates are required, the technique is likely to be a useful tool for forest practitioners in managing tree nutrition and health.