Depietion of the ozone layer is increasing the amount of UV-B radiation reaching the earths surface. The enhanced aging and mutation associated with UV-B damage suggests that crop yields may be threatened. However, plants are protected by flavonols which absorb UV-B. Although a great deal of research has been done on the flavonols, progress has been hampered by their lack of color. To overcome this problem, a staining procedure that provided sensitive and specific fluorescence identification of flavonols in Arabidopsis thaliana was developed. Three T-DNA insertional mutants, which lacked flavonols were identified, and the heritability of each has been confirmed by its multiple occurance in the parental line. The Mutants are being outcrossed, and analysis of the F2 will test if any of the mutations are tagged by a T-DNA insert. If so, the tagged gene will then be cloned.