Studies of Photosynthesis Inhibition by Phytoluminography

Abstract

Abstract Inhibition of photosynthesis by simazine or diuron, as well as disturbance brought about by darkness, fungal infections, heat, high concentrations or lack of CO 2, lead to a luminescence of chloroplasts after irradiation with photosynthetically active light. This effect is the basis of phytoluminography, a new method which may replace in many cases the tedious procedures used at present to determine the photosynthetic capacity of living plant tissue. Both qualitative analyses of luminescence images produced by an image intensifier as well as quantitative measurements using a photomultiplier are possible. Autoradiographic studies have shown that luminescence images of herbicide-damaged leaves are identical with autoradiographs of the same leaf obtained after labelling with radioactive CO 2. In contrast to autoradiography, phytoluminography does not damage the tested parts of plants nor is there danger of contamination. There is no need for expensive chemicals and skilled technicans, and immediate results are obtained. Quantitative measurements of phytoluminescence after the application of simazine and diuron (DCMU) to Elodea canadensis in submersed culture showed that approximately 1 ᴍ of inhibitor per 20 ᴍ of chlorophyll (a + b) is needed to obtain maximal luminescence, which indicated total inhibition of photosynthesis. Both luminescence and inhibition are reversible if the inhibitor is removed by dialysis.