Seasonal change of photosynthetically active radiation intercepted by a spring wheat [Triticum aestivum] canopy and its relation to dry matter production

In field trails in 1988 the leaf area, DW of aboveground plant material and the incident, reflected and penetrated PAR were measured for spring wheat cv. Hanuyutaka and Selpek. The daily mean values of diurnal changes in penetration and reflection were the same on cloudy or clear days. Penetration decreased with increasing leaf area. After flag leaf emergence, it was <10% and it changed little even when total surface area was >10 m²/m². There was a linear relationship between intercepted PAR and CGR, but above 8 MJ/m², the CGR of Hanuyutaka was almost constant (about 30 g/m² d)