Figure 1.
Diagram of Nicotiana africana showing the leaves onto which fourth-instar larvae of Helicoverpa armigera were placed for experimental purposes. Drawing by F. Venter.
Figure 2.
Larval growth and consumption.
(A) The relative growth rate (RGR) of fourth-instar Helicoverpa armigera larvae feeding on flowering Nicotiana africana plants for four days and (B) the leaf area consumed per larva (mean ± SE). One (n = 5), three (n = 15) or six larvae (n = 30) were exposed to single leaves per plant. Same letters above bars indicate no significant differences at P>0.05.
Figure 3.
Effect of herbivory on leaf alkaloid concentrations.
Effect of herbivory by Helicoverpa armigera fourth-instar larvae on (A) nicotine, (B) nornicotine and (C) anabasine concentrations (mean ± SE) in undamaged (open bars) and herbivore damaged (black bars) middle leaves of flowering Nicotiana africana plants. n = 4–30.
Table 1.
Results of generalized linear model (GLM) analyses for alkaloid concentrations in Nicotiana africana.
Figure 4.
Alkaloid concentrations in undamaged leaves after herbivory.
Effect of herbivory by Helicoverpa armigera fourth-instar larvae on (A) nicotine, (B) nornicotine and (C) anabasine concentrations (mean ± SE) in undamaged top (open bars) and undamaged bottom (black bars) leaves of flowering Nicotiana africana. n = 3–8. Same letters above bars indicate no significant differences at P>0.05.