Ecophysiological characteristics of four maize hybrids and Abutilon theophrasti

Combining empirical research with simulation modelling may improve our unde rstanding of the dynamics of crop:weed competition and for testing hypothes es on the importance of specific traits for enhancing crop performance in m ixtures. Two field experiments were conducted to quantify and compare estim ates of traits important for radiation interception and utilization in four maize hybrids and Abutilon theophrasti grown in monoculture. Early leaf ar ea growth rate did not vary among maize hybrids within a year, but varied a mong years. The response of CO2 assimilation rate to absorbed radiation and leaf nitrogen content did not differ among hybrids. Abutilon theophrasti a nd two old maize hybrids partitioned more new biomass to stem relative to r eproductive organs than newer hybrids. Old hybrids had greater specific lea f area during the period of most rapid growth, grew taller, and leaf area w as distributed higher in their canopy. Extinction coefficients for diffuse radiation did not differ among hybrids or between years. Results suggest th at these four maize hybrids may differ in their ability to intercept incide nt radiation, which may influence their ability to compete for light.