Dosimeter for the measurement of plant damaging solar UV exposures

The development of a dosimeter for the measurement of the biologically effective UV exposures (UVPGI) for plant growth inhibition in higher plants based on a recently reported action spectrum is presented. The new dosimeter is based on the two photoactive materials polysulphone and nalidixic acid, each in thin film form layered on top of one another to provide a combined response. The quantitative characteristics of the UVPGI dosimeter were measured, including the spectral response, dose response, dark reaction and cosine response. The spectral response of the new dosimeter has been successfully extended into the UVA waveband. The dark reaction was within a reasonable limit that could be taken into account when measurements are taken by measuring the post-exposure absorbances at a consistent time period after the exposure. The cosine response approximated the cosine function to better than 15% for solar zenith angles up to 50°. The dose response shows that the new dosimeter can be employed for the measurement of UVPGI exposures and has reproducibility comparable to other dosimeters calibrated to a biological action spectrum.