EFFECTS OF INTRASPECIFIC INTERFERENCE ON MAIZE LEAF AZIMUTH

Interception of solar irradiation by leaf canopies is influenced by th e canopy architecture of crops, which is a function of shape, distribu tion, and orientation of the leaves that constitute the canopy. The ob jective of this study was to test the hypothesis that leaf azimuthal d istribution in a maize (Zea mays L.) canopy is not influenced by plant density and row width. Experiments were conducted at flora, Ontario, with maize grown at 4, 7, and 10 plants m(-2) at a 0.76-m row width in 1991 and 1992 and with maize grown at 7 and 10 plants m(-2) at a 0.5- m row width in 1992. Leaf orientation was recorded in 16 azimuthal cla sses for leaves from the bottom to the topmost leaf position, Results showed that the orientation of leaves in the topmost layer (twelfth to sixteenth lean was more perpendicular to the row for high than for lo w plant densities. An azimuthal shift of leaves from the bottom to the top in maize plants was apparent in all canopies, but the shift was l arger for plants grown at high plant densities than for those grown at low plant densities and a similar trend was apparent for the comparis on of maize grown at 0.76-m vs. 0.5-m row widths. Results of this stud y suggest that the orientation of leaves in a maize canopy is altered by intraspecific interference, thereby more effectively intercepting i ncident solar irradiance.