The effects of growth temperature on changes in net photosynthetic rate (PN) and the chlorophyll fluorescence induction parameter Fv/Fm were investigated after cold stress in inbred maize lines with different degrees of cold tolerance. There was no significant difference between lines grown at optimum temperatures of 25/23 and 20/18 °C as regards PN and Fv/Fm determined at the growth temperature, but these parameters were lower for plants grown at a suboptimum temperature of 15/13 °C. After cold treatment, the decrease in PN was more pronounced in chilling-sensitive lines. The higher the growth temperature was, the more pronounced decrease occurred in PN and Fv/Fm. Thus at low growth temperature both damaging and adaptive processes occur. and T. Janda ... [et al.].
During cold treatment of Zea mays L. plants there was a decrease in the level of Fv/Fm and in the quantum yield of photosynthetic electron transport. The degree of damage depended on the ambient temperature and on the irradiance (I). The lower the temperature and the higher the 1, the more pronounced damage occurred. This suggests that photoinhibition has an important role in the cold damage to young maize. Although there was no damage in complete darkness even at low temperature, the repair processes needed a normal temperature.
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 °C (AG band), together with a B band peaking between 20 and 35 °C. Low temperature stress first caused a downshift and a temporary increase in the AG band after 4 h at 0 °C in the light, then a decrease in the AG and B TL bands after 1 d at 0 °C 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 °C 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. and T. Janda, G. Szalai, E. Páldi.