Light Measurements in Plant Growth Investigations

IT is generally agreed that the best method of measuring daylight as a part of the plant's microclimate is to integrate the light with respect to time. The total amount of light received may be noted every day or week according to the time-scale of the experiment. Several light-integrating instruments have been developed. They usually work by charging a condenser with the current from a photocell, and discharging the condenser at a fixed voltage through a counter. If the photocell response is linear, the number of counts in a given time-interval is a measure of the integrated amount of light received during that interval.