The main interest in the lab is on perception of light by two photoreceptor systems, one being the family of phytochromes, and the other being the yet uncharacterized family of blue light photoreceptors. Using mutants defective in these photosystems, we are trying to determine the physiological steps following light perception that lead to cell expansion and leaf growth. Because plant cell growth is associated with the activity of a plasma membrane proton pump, we are measuring the effect of specific wavelengths of light on various ion transport systems in growing leaf cells. Emphasis is placed on ion channels, and the possibility that a photoreceptor interacts either directly or indirectly with such a protein. We use patch clamp electrophysiology in conjunction with standard microelectrode methods to measure electrical responses. The underlying biochemistry of these responses needs to be characterized. Growth of leaves, leaf pieces, or epidermal layers is measured with position transducers, and the kinetics of the growth responses are being investigated to determine the relevance of the electrical responses of cells to light. The interaction of the ion transport mechanisms at the plasma membrane with both the mechanical loosening of the cell wall, and the functioning of the cytskeleton in growth, are also of interest.