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.