Effects of freezing on thermoluminescence in various plant species.

The aim of this study was to monitor the effect of sudden frost on the photosynthetic electron transport chain in the leaves of various plant species using the thermoluminescence (TL) technique. A short period of freezing caused a decrease in the afterglow (AG) band in young maize leaves, with a slight upshift in the maximum temperature. The B band induced by far-red (FR) illumination started to decrease at a significantly lower temperature. The flash-induced B band also showed a substantial decrease in intensity after short preliminary freezing. In contrast to other species, for which there was always a well-detectable TL signal even after relatively drastic freezing, there was no TL signal at all in geranium below a threshold temperature. The behavior of the FR-induced TL curve in cucumber plants was a mixture of that found in wheat or pea, on the one hand, and maize, on the other: the AG band gradually decreased with decreasing temperature and finally totally disappeared, as in maize. The FR-induced B band showed an upshift after freezing. These results suggest that AG is a normal component of TL bands induced not only by FR, but also by single turnover flash.