Thermoluminescence investigation of low temperature stress in maize

The thermoluminescence (TL) emission of photosynthesising materials origina tes from the recombination of charge pairs created by a previous excitation . Using a recently described TL set-up the effect of chilling stress on TL bands occurring at positive temperatures (AG, B, and HTL) was investigated in intact leaves. The far-red irradiation of leaves at low, but non-freezin g temperatures induced a TL band peaking at around 40-45 degreesC (AG band) , together with a B band peaking between 20 and 35 degreesC. Low temperatur e stress first caused a downshift and a temporary increase in the AG band a fter 4 h at 0 degreesC in the light, then a decrease in the AG and B TL ban ds after 1 d at 0 degreesC in the light. This decrease was less pronounced in cold-tolerant genotypes and in those grown at acclimating temperatures. Furthermore, an additional band appeared above 80 degreesC after severe col d stress. This band indicates the presence of lipid peroxides. Thus TL is a useful technique for studying the effects of low temperature stress.