Key points are not available for this paper at this time.
Brian M. Parks, Peter H. Quail, Phytochrome-Deficient hy1 and hy2 Long Hypocotyl Mutants of Arabidopsis Are Defective in Phytochrome Chromophore Biosynthesis, The Plant Cell, Vol. 3, No. 11 (Nov., 1991), pp. 1177-1186
Parks et al. (Fri,) studied this question.