CHANGES IN PHOTOSYNTHESIS IN INBRED MAIZE LINES WITH DIFFERENT DEGREES OF CHILLING TOLERANCE GROWN AT OPTIMUM AND SUBOPTIMUM TEMPERATURES

The effects of growth temperature on changes in net photosynthetic rat e (PN) and the chlorophyll fluorescence induction parameter F-v/F-m we re investigated after cold stress in inbred maize lines with different degrees of cold tolerance. There was no significant difference betwee n lines grown at optimum temperatures of 25/23 and 20/18 degrees C as regards P-N and F-v/F-m determined at the growth temperature, but thes e parameters were lower for plants grown at a suboptimum temperature o f 15/13 degrees C. After cold treatment, the decrease in P-N was more pronounced in chilling-sensitive lines. The higher the growth temperat ure was, the more pronounced decrease occurred in P-N and F-v/F-m. Thu s at low growth temperature both damaging and adaptive processes occur .