Thermoluminescence investigation of low temperature stress in maize

The thermoluminescence (TL) emission of photosynthesising materials originates 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-freezing 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 temperature stress first caused a downshift and a temporary increase in the AG band after 4 h at 0 degreesC in the light, then a decrease in the AG and B TL bands 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 cold stress. This band indicates the presence of lipid peroxides. Thus TL is a useful technique for studying the effects of low temperature stress.