FREE-RADICAL PROCESSES INDUCED BY DESICCATION IN GERMINATING MAIZE - THE RELATIONSHIP WITH RESPIRATION AND LOSS OF DESICCATION TOLERANCE

Using germination of maize as a model, desiccation-induced free radica l processes were studied with the object of understanding desiccation tolerance. Several significant elements of damage were observed in des iccated material associated with development of desiccation intoleranc e: increased lipid peroxidation, phospholipid de-esterification, build -up of a stable free radical, supression or repression of respiratory enzymes from complex I, II and IV, An EPR (electron paramagnetic reson ance) response was also detected in isolated mitochondria following in vitro desiccation. The loss of desiccation tolerance appeared to be d ependent on oxygen concentration. Two highly significant correlations were independently found between respiration rates and production of a stable free radical detected by EPR. These data suggest that respirat ion is an important factor in the loss of desiccation tolerance. We pr esent a model suggesting that activated oxygen formation during desicc ation originates in the disruption of the mitochondrial electron trans port chain with increasing leakage to oxygen so generating irreversibl e and lethal peroxidative damage, leading to the development of desicc ation intolerance.