# Light 


Light photoperiod is calculated as detailed in 
 Section @ref(Photoperiod). Photoperiod affects wheat phenology. 

Light intensity and photoperiod also have an effect on diffuse light
fraction, so that it could impact
the diffuse factor ($f_{d}$; Equation \@ref(eq:BiomassProduction);  Section @ref(Radiation-limited-biomass))
and reduce the radiation-limited biomass accumulation ($\Delta Q_{r}$;
 Section @ref(Radiation-limited-biomass)). However, in the current
APSIM-Wheat, the diffuse factor equals to 1 (i.e. no impact of diffuse
light on biomass production). 

Light intensity affects

* radiation-limited biomass accumulation ($\Delta Q_{r}$;  Section @ref(Radiation-limited-biomass))
via the radiation interception ($I$; Equation \@ref(eq:RadiationInterception)),
which depends on the incoming radiation ($I_{0}$) and on a light-interception
factor ($f_{h}$ ) based on the canopy width. However, this canopy
factor has no impact in the current version of APSIM-Wheat ($f_{h}$
= 1), 
* LAI senescence under low light condition ($\Delta LAI_{sen,\,light}$;
Equation \@ref(eq:SensLight)).