Blue Light Induction of Barley Leaf Unfolding. A Phytochrome Reaction?

Abstract Low‐energy blue light (450, 475 nm) has been found to induced unfolding of etiolated barley leaves (Hordeum rulgare cv. Ingrid). This induction can be reversed by far‐red light. Barley leaf unfolding is normally stimulated by red light, reversed by far‐red light, and can be considered to be a typical phytochrome controlled response. It is possible to explain the effects by red and blue light as mediated by the same photoreceptor. The phototransformation of this pigment results in two forms, P2 and P4, to which physiological activity can be ascribed. The red and blue light affect different steps in a cyclical photoconversion. Calculated theoretical dose response curves are presented for such a model in agreement with the experimental data.