Instruments for the Measurement of Photosynthetically Active Radiation and Red, Far-Red and Blue Light

(1) The design of an instrument for the simultaneous measurement of photosynthetically active radiation and red, far-red and blue light is described. The optical responses of the instrument closely match the action spectra of photosynthesis and some important photomorphogenic responses within the waveband of 400 to 800 nm. (2) The design of a single instrument for the measurement of the quantum irradiance at 660 and 730 nm is also shown. (3) The application of these instruments to measurements in the field and the controlled environment is described.