ALKALOIDAL RESPONSES TO DAMAGE IN NICOTIANA NATIVE TO NORTH-AMERICA

We performed field tests of alkaloid induction in Nicotiana attenuata plants growing in southwestern Utah with mimicry of the two major type s of damage inflicted by invertebrate and vertebrate herbivores: leaf damage and stalk removal, respectively. In undamaged plants, seasonal increases in leaf nicotine content occurred at a rate of 0.046% leaf d ry mass/day. Leaf damage doubled the accumulation rate to 0.086-0.138% leaf dry mass/day, while stalk removal resulted in a quadrupling of t he accumulation rate to 0.206% leaf dry mass/day. These damage-induced increases in nicotine accumulation are significantly larger than betw een-plant and phenological variations. Leaf damage to the nornicotine- (N. repanda and N. trigonophylla) and anabasine-accumulating (N. glauc a) Nicotiana species native to North America resulted in 1.5- to 5-fol d increases in their principal leaf alkaloid pools. We conclude that a lkaloid induction is not limited to nicotine-accumulating Nicotiana sp ecies and that herbivores feeding on previously damaged plants are lik ely to encounter tissues with alkaloid titers significantly higher tha n those of undamaged plants.