Fig. 2.

Plant responses to herbivory in Penstemon virgatus above-ground biomass (A) and water content (B). (C) Percentage dry weight of iridoid glycosides, divided into the two major individual compounds, catalpol and scutellarioside, for control (C) and herbivore-damaged plants (H) across three early plant developmental stages (i.e. 1- and 2-month-old plants are considered seedlings and 3-month-old plants are considered early juvenile stages). Asterisks represent mean group differences among treatments as tested by single degree of freedom contrasts. Significance is displayed as: ***, P < 0·001; **, P < 0·01; *, P < 0·05. In panel (C) significance is displayed only for scutellarioside, as the percentage of catalpol did not vary among treatments (see Table 1).