Morphological changes and enzyme activity in suspension-cultured cells of Citrus aurantium were followed after chitin elicitation. Chitin oligomers presented a rapid effect with a maximum activity after 3 h followed by a gradual decrease to the original levels at 8 h of incubation. Cell walls presented a lignification process and the cytoplasmatic protein became less reactive to anionic stains. In the treated material a reduction in starch grain size, an increase in the number of autophagic vacuoles, deposition of secretion in the pericellular space and a defibrillation of the cell-wall polymers were observed. Chitin oligomers increased peroxidase and L-phenylalanine ammonia-lyase activities. Extracellular peroxidase activity increased from 0.20 U mL-1 after 1 h to 0.45 U mL-1 at 3 h followed by a gradual decrease up to 8 h. The peroxidase isoenzyme pattern revealed a predominance of basic isoenzymes in these cells.
chitin; Citrus aurantium; elicitation; L-phenylalanine ammonia-lyase; peroxidase
