This invention pertains to the discovery of mutant phytochromes that when introduced into a plant alter the photomorphogenic properties of that plant. In certain embodiments transfection of plants by nucleic acid constructs expressing the mutant phytochromes produced plants having a phenotype characterized by light-independent activation. Thus, in certain embodiments, this invention provides a transgenic plant or plant cell comprising a mutant phytochrome where the mutant phytochrome is a light-stable phytochrome; and the transgenic plant shows decreased shade avoidance as compared to the same species or strain of plant lacking the mutant phytochrome. In various embodiments the mutant phytochrome comprises a mutation at the position corresponding to tyrosine residue 276 in an Arabidopsis phytochrome where the mutation is to a residue other than tyrosine.