Fig. 1. Evolution of (a) total chlorophyll, (b) carotenoids, and (c) nitrogen in uppermost fully expanded leaves of cotton, n = 69. Vertical arrows indicate sampling dates on which both leaf and canopy reflectance were measured (n = 22); these data were subsequently used in correlation analysis (see Fig. 3, 4, 5, and 6). Leaf and canopy reflectance measurements were obtained only once, on 23 August, in the 0% of control N at boll-filling onward treatment.