Thermoluminescence: a technique for probing photosystem II.

The noninvasive technique of thermoluminescence (TL) monitors recombination reactions of oxidized donors and quinone acceptors of photosystem (PS)II leading to light emission. The technique is simple, inexpensive, and yet powerful in probing PSII using leaf discs, algal cells, thylakoids, or PSII preparations. The procedure for obtaining glow curves from photosynthetic material has been described. Interpretation of the obtained data requires a thorough understand-ing of the charge pairs responsible for generating different TL bands. This chapter discusses characteristics of different TL bands to facilitate interpretation. Thermoluminescence and delayed light emission (DLE) are related to each other and each TL band represents one component of delayed light. The technique has found application in monitoring several aspects of the PSII electron transport. Through the possibility of interpreting changes in the redox potentials of donors and acceptors on the basis of a shift in glow peak temperature, the technique should prove useful in understanding the process of adaptation, responses to abiotic and biotic stresses, and structural modifications in the PSII polypeptides.