A comparison of two techniques for nondestructive measurement of chlorophyll content in grapevine leaves
Traditional methods for chlorophyll (Chl) measurement include wet chemical extractions and handheld Chl meters. The recent availability of small and affordable radiometers has provided means to estimate Chl from reflectance measurements. This paper compares the performance of a handheld SPAD Chl meter and a recently developed Red Edge Chlorophyll Index (CIred edge) for Chl estimation in grapevine (Vitis spp.) leaves. Leaves were sampled and Chl was quantified using these two methods. Both techniques were compared against grapevine-leaf Chl as analyzed using standard laboratory procedures. Both SPAD and CIred edge were equally accurate in measuring Chl < 300 mg/m2. However, at higher Chl, SPAD sensitivity declined and the CIred edge accuracy was much higher than that of SPAD. The Chl index was found to be capable of accurately estimating pigment contents across a greater range than the SPAD, thus it can be used for quantitative assessment of early stages of plant stress.