hey i just ran across this study done in 1994. ill just show a couple cut outs and the conclusion because its pretty long i found the read very interesting....
here is the page: (
http://ncr101.montana.edu/Light1994C...ing%20text.htm)
here is the web site:
http://ncr101.montana.edu/Light1994Conf/index.htm International Lighting in Controlled Environments Workshop
<hr> UV FILTERS FOR LIGHTING OF PLANTS (Short Report)
T. Döhring, M. Köfferlein, S. Thiel, H.K. Seidlitz, and H.D. Payer
The wavelength dependent interaction of biological systems with radiation is commonly described by appropriate action spectra (Caldwell et al. 1986). Particularly effective plant responses are obtained for UV radiation. Excess shortwave UV-B radiation will induce genetic defects and plant damage. As an example the action spectrum of DNA damage is plotted in Figure 1. Due to the strong wavelength dependence of this action spectrum, a shift of the UV absorption edge of the radiation spectrum towards shorter wavelengths will effect a significant increase of DNA damage. A 13% decrease of the ozone column from 320 DU to 280 DU, for instance, will result in a 36% increase of DNA damaging irradiation.
Besides the ecological discussion of the deleterious effects of the excess UV radiation there is increasing interest in horticultural applications of this spectral region. Several metabolic pathways leading to valuable secondary plant products like colors, odors, taste, or resulting in mechanical strength and vitality are triggered by UV radiation. Thus, in ecologically as well as in economically oriented experiments the exact generation and knowledge of the spectral irradiance, particularly near the UV absorption edge, is essential......
The standard UV filtering in these chambers is performed by layers of borosilicate glass (Tempax, and Pyran,) which exhibits a steep absorption edge near 300 nm. The respective UV monitoring and spectral measurements have to be performed with high precision and accuracy. This spectral measurement can only be achieved by a double monochromator providing the required wavelength resolution with a maximum of straylight rejection and with dynamics of about 6 decades.
CONCLUSIONS Different filter glasses are available which provide absorption properties suitable for gradual changes of the spectral UV-B illumination of artificial lighting. Using a distinct set of lamps and filter glasses an acceptable simulation of the UV-B part of natural global radiation can be achieved. The ageing of these and other filter materials under the extreme UV radiation in the lamphouse of a solar simulator is presently unavoidable. This instability can be dealt with only by a precise spectral monitoring and by replacing the filters accordingly. For this reason attempts would be useful to develop real ozone filters which can replace glass filters. In any case chamber experiments require a careful selection of the filter material used and must be accompanied by a continuous UV-B monitoring.
Ok well half the shit i really didn't have a clue as to what they were talking about but after reading through the report a couple times, i pretty much gather with the proper setup of light you can achieve a close representation of the actual spectrum that the sun gives out. but you need to use glass filters, and in time those glass filters become useless due to the advanced aging they were subjected to under the uv lighting. if some one could go and check this out as to bring their thoughts on this please by all means say something.