An instrument capable of imaging chlorophyll a fluorescence from intact leaves at very low irradiance and at cellular and subcellular levels of organization

An instrument capable of imaging chlorophyll a fluorescence, from intact leaves, and generating images of widely used fluorescence parameters is described. This instrument, which is based around a fluorescence microscope and a Peltier-cooled charge-coupled device (CCD) camera, differs from those described previously in two important ways. First, the instrument has a large dynamic range and is capable of generating images of chlorophyll a fluorescence at levels of incident irradiance as low as 0.1 μmol m^?2 s^?1. Secondly, chlorophyll fluorescence, and consequently photosynthetic performance, can be resolved down to the level of individual cells and chloroplasts. Control of the instrument, as well as image capture, manipulation, analysis and presentation, are executed through an integrated computer application, developed specifically for the task. Possible applications for this instrument include detection of early and differential responses to environmental stimuli, including various types of stress. Images illustrating the instrument's capabilities are presented.