<i>IN VIVO</i> MEASUREMENTS OF THE PHYTOCHROME PHOTOSTATIONARY STATE IN FAR RED LIGHT

Abstract

Abstract— The in vivo photostationary state, ϕ fr = ([ P fr ] fr /[ P ]), of phytochrome in far red light has been determined in mustard seedling cotyledons by three different methods. The ϕ fr is a function of the length of time of etiolation ( t = 36 hr, ϕ fr = 0·14; t = 72 – 120 hr, ϕ fr = 0·075). The calculated ϕ r = 0·8. The amount of P tot is strongly dependent on the time of onset of far red light. These data imply that it would be almost impossible to maintain a constant level of P fr in mustard cotyledons over a considerable period of time.