Fig. 4. Relationship between kernel number per plant (expressed as relative values) and plant growth rate during a 30-d period bracketing silking for maize hybrids Asgrow 777 (Exp. 5), SPS 240 (Exp. 6), Dekalb 636 (Exp. 7), and Dekalb 639 (Exp. 8) growing under variable levels of nitrogen or water availabilities. KNP values for each hybrid are expressed relative to those obtained for the control without deficiencies. PGR is expressed per unit time (a) or per unit thermal time (b). Each point is the average of three replications. Plants did not show prolificacy, so kernel number per plant was equal to kernel number per uppermost ear. The reference data from Fig. 1 (with KNP data also expressed as relative values), the equation fitted to these data (solid line) and its 95% prediction interval (dashed lines) are also shown. KNP values corresponding to a relative value of 1 were 520, 385, 465, and 600 for Exp. 5 (a, b, and c), 6 (a and b), 7, and 8, respectively. SE of the means in absolute values ranged from 0.11 to 0.40 g d^-1 for PGR and from 4 to 16 kernels for KNP. Equations fitted to reference data (n = 34) were KNP = 1.0(PGR-1.17)/[1+0.67*(PGR-1.17)] (R² = 0.88) for Fig. 4a; and KNP = 8.97(PGR-0.06)/[1+5.36(PGR-0.06)] (R² = 0.83) for Fig. 4b.

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