Barley Leaf Unfolding under Mixtures of Red and Blue Light

Barley leaf unfolding is stimulated by mixed red and blue light. However, the stimulation from mixed light is attenuated when compared with the stimulation from red light alone, particularly for low intensities of the mixed light and for short irradiation times. For higher light intensity mixtures of red and blue light and for longer irradiation times, the blue light enhances the stimulation from red light and vice versa. This supports the assumption that the blue light effect in this case is also mediated by the phytochrome system. Furthermore the present findings point to the possibility of competitive reactions caused by red and blue light in the excitation of phytochrome.