EAR POSITION AND VERTICAL-DISTRIBUTION OF LEAF-AREA IN CORN

Leaf area distribution determines the interception of radiation for photosynthesis. A method of analysis was developed to quantifiy differences in vertical leaf area distribution in a corn (Zea mays L.) canopy. A third-order polynomial accurately described the relationship between leaf area index (LAI) and plant height (both normalized with respect to their maxima) for a range of normal and "leafy" licensed and experimental plant lines during the late vegetative and early grainfilling stages (r2 greater-than-or-equal-to 0.85). The shape of the polynomial reflected the bell shape of individual leaf area versus leaf number curves, with the densest leaf area in the mid-portion of the canopy. When ear position was marked on the polynomial plot, the proportion of leaf area above the ear was easily compared among lines. The proportion of total LAI above the ear varied from 0.52 to 0.83 in 1986 and from 0.63 to 0.86 in 1987. The actual LAI above the ear was in a relatively narrow range of 2.0 to 3.2 for all tested licensed lines. The analysis described will facilitate comparison of ear position and vertical distribution of leaf area among different plant lines and crop management practices.