PHYTOCHROME INTERMEDIATES IN VIVO– III KINETIC ANALYSIS OF INTERMEDIATE REACTIONS AT LOW TEMPERATURE

Abstract
Abstract— Kinetic experiments have provided evidence for a series of light and dark reactions of phytochrome intermediates at low temperature in Pisum epicotyl tissue. A photoequilibrium exists between Pr and P698, and between Pfr and P650. A dark reversion of P698Pr and P650pfr at –70°C has been demonstrated. When cooled to 70°C under incandescent light, most of the phytochrome in the tissue is driven into photochemically unreactive intermediates. About 2% of the phytochrome remains as weakly absorbing intermediates that form Pr and Pfr in darkness. A scheme is presented for phytochrome phototransformation in vivo.