Leaf Angle, Tassel Morphology, and the Performance of Maize Hybrids 1

The relative importance of leaf orientation, planting densities, planting patterns, and tassel shading on grain production of certain maize (Zea mays L.) genotypes was investigated. Three experiments were conducted over a 4-year period to ascertain the effect of leaf angle on grain yield and percentage of unproductive plants in several maize hybrids. A plant-density experiment using normal, liguleless-l, and liguleless-2 leaf types at densities of 60,000, 75,000, and 90,000 plants/ha in 50.8 cm row spacings was conducted over a 3-year period. The liguleless-2 hybrids produced 6.7% and 12.9% more grain at 75,000 and 90,000 plants/ha, respectively, than the normal leaf type hybrids. A plant-spacing experiment using 1,290 cm2 and 645 cm2/plant and the same three leaf types was grown over a 2-year period. The liguleless-2 hybrids produced 9.7% and 49.7% more grain at 1,290 cm2 and 645 cm2 (25.4 ✕ 25.4 cm) plant spacings, respectively, than the normal leaf type hybrids. In both experiments an increase in unproductive plants was associated with a reduction is grain yields. An additional 1-year experiment was conducted to determine if light penetration into the leaf canopy and tassel morphology could account for the increased grain yield of liguleless-2 hybrids. The normal leaf type hybrids had only 89% as much incident light in the leaf canopy as the liguleless- 2 hybrids. In addition, tassel removal increased grain yield of the normal leaf type hybrids but not that of the liguleless-2 hybrids. Based on results of this study, leaf angle and tassel morphology were two characters associated with increased grain yield of liguleless-2 hybrids under high plant densities and narrow row spacings. Liguleless-I hybrids have almost a total vertical leaf orientation and did not respond in the same manner in these experiments as liguleless-2 hybrids, although the leaf angle and light penetration into the canopy were greater than liguleless-2 hybrids. Responses of liguleless-1 hybrids were similar to those of normal hybrids.