Action Spectra for Ultraviolet Killing and Photoreactivation in the Blue‐green Alga Agmenellum Quadruplicatum

The action spectrum for photoreactivation has been determined in a coccoid blue‐green alga, Agmenellum quadruplicatum. The spectrum is rather similar to that recorded for Streptomyces griseus conidia, with some suggestion of a little more structure. The action spectrum suggests possible carotenoid involvement; however, no other evidence for this could be found. The action spectrum for u.v. killing is also broad with some evidence of fine structure. The possible implication of tetrahydropteridines or c‐phycocyanin as chromophores in the region 240–300 nm, along with DNA, is pointed out.