CHANGES IN THE CHLOROPHYLL FLUORESCENCE PARAMETERS AND SUPEROXIDE DISMUTASE ACTIVITY DURING HEAT SHOCK TREATMENT AND THE RECOVERY PERIOD IN TOMATO PLANTS
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Instituto Nacional de Ciencias Agrícolas
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Plants of tomato cv Amalia were exposed to heat shock of 45oC for two and three hours. After stress conditions, a group of plants was recovered under normal growth conditions of temperature of 25/20oC day/night, relative humidity of 60 % and a photon flux density of 250 ¿mol photons.m-2.s-1 PAR. Furthermore, they were recovered at 25oC for 20 hours. An initial fluorescence increase and a variable fluorescence decrease were detected in stressed plants by both stress conditions. A photochemical efficiency decrease was noted during stress. After the recovery period (20 hours), fluorescence parameters showed a significant recovery, except the photochemical efficiency. SOD total activity was reduced by heat shock; however, several isoenzymes did not show a similar sensitivity to high temperature. Fe-SOD showedresistance to high temperature, whereas Cu/Zn-SOD was thermosensible. Thus, 20 hours of recovery were considered sufficient to restore SOD activity.
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