Thermoluminescence (TL) Measurements in Tobacco Leaves

Abstract

TL measurement is a useful tool for studying charge stabilization and subsequent recombination in photosystem II (PSII) in higher plants and cyanobacteria. Recombination of positive charges stored in the S2 and S3 oxidation states of the water oxidizing complex with electrons stabilized on the reduced QA and QB acceptors of PSII results in characteristic TL emissions. The TL intensity reflects the amount of recombining charges and the peak temperature is indicative of the energetic stabilization of the separated charge pair: the higher the peak temperature, the greater the stabilization. Illumination of single-turnover flash with the plant or cyanobacterial sample after a short dark adaptation induces a major TL band, called the B band which appears around at 30 °C and arises from S2/S3QB- recombination. If electron transfer between QA and QB is blocked by DCMU, the B band is replaced by the so-called Q-band arising from S2QA- recombination at around 10 °C. Illumination with a series of single-turnover flashes result in B bands oscillating with a period of 4, with a maximum at the second flash. Here we mainly described the measurements of TL B-band (charge reccombination of S2/S3QB-), Q-band (charge reccombination of S2QA-,) and period-four oscillation of the intensity of the B-band in tobacco leaves.