Anwendung der periodischen chemischen Relaxation auf die Photosynthese

Abstract

AbstractThe transient absorption changes which occur during the primary process of photosynthesis are sometimes so small that they cannot be detected even by sensitive photometric methods using the single flash technique (transmission change: 10−3, time resolution: 10−5 sec [1]). The signal‐to‐noise‐ratio, however, can be improved by the periodic relaxation technique by a factor of 200 [2]. In this way, the measuring range is extended to transmission changes < 10−5, time resolution 10−5 sec.1. By use of the periodic method new absorption changes were detected which might be ascribed to new intermediary products. At several wavelenghts various small absorption changes are superposed to an overall signal which itself is completely masked by the noise level. Even in this case the different absorption changes can be separated and recorded with high S/N‐ratio by means of compensation.2. As no absorption changes are connected with intermediary products of the H2O‐splitting reaction of photosynthesis there is no information on the mechanism of water‐splitting at all. – On exciting broken chloroplasts by means of periodic groups of flashes of light and measuring the O2‐production as function of flash‐interval two reaction time constants τ1 = 1 msec, τ2 = 100 msec could be detected. These time constants might be ascribed to two different transient products in the chain of the H2O‐splitting reaction.