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SPAD meter versus tristimulus colorimeter to estimate chlorophyll content and leaf color in sweet pepper
- Madeira, A.C., Ferreira, A., Varennes, A. de., Vieira, M.I.
- Communications in soil science and plant analysis 2003 v.34 no.17-18 pp. 2461-2470
- meters (equipment), Capsicum annuum, sweet peppers, leaves, color, chlorophyll, colorimetry, reflectance
- The chlorophyll content and leaf color were estimated in leaves of sweet pepper by using the SPAD-502 chlorophyll meter and the Minolta tristimulus colorimeter. In situ SPAD readings and extractable chlorophyll content were highly correlated, both for chlorophyll a (r2 = 0.93) and total chlorophyll (r2 = 0.89). Light reflectance (400-700 nm) measured with the tristimulus colorimeter was compared with light transmittance (at 650 and 940 nm) measured with the SPAD-502 meter. Strong linear relationships (r2 greater than or equal to 0.93) were found between L* (lightness) and b* (yellow color) and the SPAD chlorophyll readings. However, a more correct form to measure leaf color is obtained from the calculation of the saturation chroma C* and the hue angle H degrees. Linear and quadratic regression models were obtained between C* and H degrees, and SPAD readings (r2 = 0.95 and r2 = 0.90, respectively), suggesting that both instruments may be used to estimate either chlorophyll content or leaf color.