Fig. 2. Coefficient of determination (r²) versus denominator wavelength () for relationships of leaf total chlorophyll (a + b) concentration with leaf reflectance (R), transmittance (T), and absorptance (A) band ratios. Regressions were based on linear or quadratic models as indicated atop the figure and data combined among the four planar-leaved species (168 samples). Ratios were computed by dividing R, T, or A at the best-fit indicated in Fig. 1 by R, T, or A, respectively, at each throughout the 400- to 850-nm spectrum. Where numerator and denominator were identical, ratio values remained at unity regardless of chlorophyll concentration, yielding r² = 0. These points were deleted from the figure to eliminate r² = 0 spikes.