THE INDUCTION OF SOLUBLE PEROXIDASE-ACTIVITY IN BEAN-LEAVES BY WIND-INDUCED MECHANICAL PERTURBATION

The induction of defense-related peroxidase (POD) activity in plants o ccurs in response to many biotic and abiotic stimuli. This controlled greenhouse study was an attempt to provide insight into the nature of the induction of soluble POD activity by noninjurious wind-induced mec hanical perturbation (MP). In a time course study, exposure of common bean (Phaseolus vulgaris) seedlings to daily periods of fan-produced w ind induced a significant and sustained increase in soluble POD activi ty in primary leaves of 7-9-d-old seedlings. In a wind-gradient study, wind-induced MP led to increases in soluble POD activity in leaves th at were proportionally related to the wind speed experienced by indivi dual seedlings. Wind-induced MP enhanced soluble POD activity to a deg ree similar to treatment with 5 mmol/L HgCl2, a potent oxidizing elici tor of POD activity in plants. However, no further increases in POD ac tivity were induced by HgCl2 on plants that were preconditioned with w ind-induced MP. Finally, shea periods of brushing-induced MP enhanced soluble POD activity to the same degree as longer periods of wind-indu ced MS, suggesting a greater sensitivity to thigmic stimuli than to se ismic stimuli in leaves of bean seedlings. This study illustrates the potential importance of wind and other mechanical stimuli as inducers of POD activity and interacting factors in the elicitation of POD acti vity by other environmental stimuli.