A sensor for microclimatic measurement of photosynthetically active radiation in a plant canopy

A photosynthetically active radiation (PAR) sensor has been described and t ested, the sensor is so small that it can be placed directly on a leaf in t he canopy. It is inexpensive to produce and several can be used in the cano py at the same time to obtain realistic measurements of irradiance distribu tion. Its characteristics satisfy the PAR sensor requirements, and correlat ion to a standard commercial sensor is better than 0.97. Spectral response, cosine relationship, stability and calibration are described, as well as i ts construction and electronics. (C) 1999 Elsevier Science B.V. All rights reserved.