Fig. 3. Crop growth (CG) during the effective grain-filling period as a function of (A) the amount of intercepted photosynthetic active radiation (IPAR), and (B) radiation use efficiency (RUE) during this stage. Data points represent the mean values of each treatment (plant population x row spacing x hybrid) in E₂, E₃, and E₄. Black symbols, hybrids of small kernel weight (full symbols crops in narrow rows, NR; empty symbols crops in wide rows, WR); gray symbols, hybrids of large kernel weight (dark gray crops in NR, light gray crops in WR). The lines indicate the model fitted to the data set.