Estimation of Chlorophyll Contents by Correlations between SPAD-502 Meter and Chroma Meter in Butterhead Lettuce.

Chlorophyll content of butterhead lettuce leaves was estimated by correlations between the Minolta SPAD-502 and Minolta chroma meter CR 300. The SPAD-502 readings and extractable chlorophyll (Chl a, Chl b, and total Chlorophyll) contents were related. High linear correlations were obtained for chlorophyll a (R2=0.90), chlorophyll b (R2=0.85), and total chlorophyll (R2=0.92). After that, during the growth cycle of butterhead lettuce grown in soilless culture, leaves were selected and SPAD-502 and chroma meter readings were made. Finally, correlations between SPAD-502 readings and leaf color (L*, a*, b*, C*, and hue angle) determined by the chroma meter were calculated. Hue angle (H°; R2=0.75) and lightness index (L*; R2=0.68) were the parameters that better relate with SPAD-502 readings, so these parameters can also be used for rapid and nondestructive estimates of leaf chlorophyll in situ. [ABSTRACT FROM AUTHOR]