Temporal effects on jasmonate induction of anti-herbivore defense in Physalis angulata:: seasonal and ontogenetic gradients

Patterns of defensive enzyme (polyphenol oxidase (PPO)) induction were examined in Physalis angulata L. (cutleaf ground cherry) across seasonal and ontogenetic time gradients, in response to foliar jasmonic acid (JA) application. These studies showed strongest JA induction of PPO activity in young plants and during the month of July (mid-summer). In older plants, JA treatment was correlated with a decrease in PPO activity, and no significant effects of JA treatment were observed beyond September. Developmental patterns of induction corresponded with published studies of defense induction in other species, indicating active defense of young tissues and potential shifts in defensive strategy as plants transition from growth to reproduction. Peak induction during summer corresponds with periods of high solar irradiance and herbivorous insect populations, both of which are stresses against which PPO has been demonstrated effective. (C) 2003 Elsevier Ltd. All rights reserved.