Differences in canopy structure, light interception and crop production in two Zea mays hybrids with different leaf curvatures.

E. DAVID FORD1, ALLISON COCKE1, LINDSEY HORTON1, & ELIZABETH VAN VOLKENBURGH2.

1College of Forest Resources, University of Washington, Seattle, WA98195-2100, USA, 2Department of Biology, University of Washington, Seattle, WA98195-1800, USA.

ABSTRACT
Productivity of an upright-leafed hybrid of maize, Pioneer 3394 was greater than that of a more horizontal-leafed hybrid Pioneer 3306 at planting densities of both 64,000 (LD) and 95,095 (HD) plants.ha-1 although 3394 produced less L and absorbed less light at both densities. At LD the frequency distributions of leaf area receiving illumination at different values show that in the upright-leafed hybrid there is greater penetration of light to the lower canopy, below the ear, and a greater proportion of foliage is illuminated above an assumed light compensation point of 100 µmol s-1 m-2 supporting the hypothesis that more upright leaves increase canopy efficiency through "greater light penetration" into the canopy. However, while 3394 has greater productivity and more total L at HD than LD, it has a lower area illuminated above the compensation point. The difference between LD and HD canopies of 3394 is that the HD upper canopy has a smaller area receiving high photon flux densities and we suggest its increased canopy efficiency is due to an "avoidance of photoinhibition" by upper canopy leaves and that both hypotheses, "greater light penetration" and "avoidance of photoinhibition" should be considered when considering canopy efficiency.