- The photoperiod of the lower instantaneous PPF level is usually significantly longer than that of
the higher instantaneous PPF level (Figure 2A), although the two photoperiods could be made
different in other ways or even be made equal. - The two instantaneous PPF levels with their respective photoperiods may be applied either
simultaneously or alternately (Figure 2A and B). - The two instantaneous PPF levels may be generated by the same kind of light source (homoge-
neous lighting) or different kinds of light source (heterogeneous or hybrid lighting), the latter be-
ing either artificial or solar.
B. Types of Composite Lighting
Based on the enumerated essential features, the six types of composite lighting (Figure 3) are as follows:
- Simultaneous hybrid solar-artificial composite lighting— c ombination of instantaneous PPF
from solar radiation and instantaneous PPF from an artificial light source, both applied concur-
rently generally according to diurnal (or daily) cycles - Alternating hybrid solar-artificial composite lighting— c ombination of instantaneous PPF from
solar radiation and instantaneous PPF from an artificial light source, applied in sequence or al-
ternately generally according to diurnal (or daily) cycles - Simultaneous hybrid artificial composite lighting— combination of instantaneous PPF from one
artificial light source and instantaneous PPF from a second artificial light source, both applied
concurrently generally according to diurnal (or daily) cycles - Alternating hybrid artificial composite lighting—combination of instantaneous PPF from one
artificial light source and instantaneous PPF from a second artificial light source, applied in se-
quence or alternately generally according to diurnal (or daily) cycles - Simultaneous homogeneous composite lighting— c ombination of two instantaneous PPF levels
from one artificial light source, both applied concurrently generally according to diurnal (or
daily) cycles - Alternating homogeneous composite lighting— c ombination of two instantaneous PPF levels
from one artificial light source, applied in sequence or alternately generally according to diurnal
(or daily) cycles
COMPOSITE LIGHTING FOR PLANT FACTORIES 917
Figure 3 Six types of composite lighting for controlled-environment plant production.