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organisms in nature are exposed to the full spectrum of solar radiation for days, weeks
or longer. Thus, BSWF derived from such action spectra need to be tested in
polychromatic radiation. Ideally, this should include longer wavelength radiation at
rather high flux, as occurs in sunlight.
2.2. SOME EXAMPLES OF TESTS OF BSWF
There are data sets in the literature and experiments still in progress in which the
explicit goal was to test BSWF under polychromatic radiation. There are also a number
of data sets that involve tests of BSWF with polychromatic radiation, even though this
was not the primary purpose of the work. A collection of data sets are briefly reviewed
here and the salient results summarized. The polychromatic radiation was from lamps,
solar radiation or a combination of these. A reasonable test should include
polychromatic combinations of some rather different wavelength compositions.
Hunter et al. [30] compared the effects of solar UV on anchovy larvae survival
with that from filtered fluorescent sunlamps in the laboratory. The two dose response
relationships were considerably different when plotted with dose as total unweighted
UV-B radiation (Figure 6a). However, if the UV from the two sources was weighted
with a BSWF based on an action spectrum they developed for larval survival, the two
dose-response relationships overlapped (Figure 6b). This was not the primary goal of
their work, but serves to suggest that this BSWF provided a realistic biologically
effective radiation calculation for radiation sources of very disparate spectral
composition.
In a similar fashion using combinations of polychromatic radiation from lamp
systems, from filtered sunlight, or both, several tests of BSWF have been reported. Plant
stem elongation was tested under different spectral distributions of radiation from a
xenon arc lamp in a growth chamber and in the field under a combination of sunlight
and filtered fluorescent UV lamps [31]. The generalized plant BSWF fit well at shorter
wavelengths (<310 nm) but underestimated the response at longer UV-B and UV-A
wavelengths. Mazza et al. [32] used different combinations of filtered sunlight to
establish that induction of UV-B-absorbing compounds (e.g., flavonoids) was largely
the result of exposure to shorter wavelengths (<315 nm) and was reasonably consistent
with the generalized plant spectrum. Similar results were reported with different species
by Krizek et al. [33].
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