Fig. 1. Heterosis based on midparent values for leaf CO₂ exchange rate (CER) at silking (CER0), 2 wk postsilking (CER2), 4 wk postsilking (CER4), and 5 wk postsilking (CER5), and grain yield, total dry matter (TDM), aboveground dry matter (ADM), root dry matter (RDM), root-to-shoot ratio (R/S), and harvest index (HI). * Significantly different from zero at P < 0.05; ** Significantly different from zero at P < 0.01; and NS = not significantly different at P < 0.05.