Radiation Environment of Growth Chambers1

Abstract

Abstract Radiation measurements with different types of meters in several controlled environment facilities have been compiled to demonstrate the problems associated with insuring uniform radiation levels in separate faciities. Data are provided for a quantum meter, three photometers, a pyranometer and a far-red energy meter. Significant variations in total radiant energy in chambers under similar photosynthetically active radiation (PAR) levels were demonstrated. Measurement of light under cool white fluorescent and incandescent lighting with calibrated photometers from different manufacturers, varied by 20%. Greater variation occurred when photometer measurements were compared under different types of lamps. One of the most significant variations in different chambers was the intensity of incandescent radiation. This could only be effectively monitored and controlled with the far-red sensor. Factors are given for conversion between quantum, photometric and radiometric measurements, but high precision cannot be assumed in the use of these factors because of the differences in instrument sensitivity and variations in spectral output of lamps. The study documents the need for calibration of instruments under the same type of light source that is utilized in the growth chambers and for the use of more than one type of sensing instrument to quantify the radiation that controls plant growth.