“…A number of photoactive materials were considered: Nalidixic acid (Tate et al, 1979), 8-methoxypsoralen (Diffey andDavis, 1978), phenothiazine (Diffey et al, 1977, Wong and Parisi, 1996, Parisi and Kimlin 2004, allyl diglycol carbonate or CR-39 (Wong et al, 1992, Wong et al, 1995, polyphenylene oxide or PPO (Davis et al, 1976b, Berre and Lala, 1989, Lester et al, 2003, diazochromic film (Ali and Jacobson, 1980, Jackson, 1980, Mosely et al, 1984, benoxaprofen (Diffey et al, 1982) and triphenyl tetrazolium chloride dye doped in poly vinyl alcohol (PVA) and poly vinyl butyral (PVB) (Ebraheem et al, 2000). Nalidixic acid was identified as being the most appropriate candidate to investigate further for use with polysulphone, due to the appropriate ease of handling and a response spectrum that extends into UVA wavelengths with a spectral response in the range of 280-350 nm (Tate et al, 1979) that may result in an approximation of the plant growth inhibition action spectrum when combined with PS in a combined dosimeter.…”