Table 1.
Summary of statistical results (ANOVA) comparing Penstemon virgatus responses in above-ground biomass, water content and iridoid glycosides, across three plant developmental stages, 1 week after the herbivores were removed from treatment plants. Significant results (P < 0·05) are highlighted in bold
| Source of variation | d.f. | Biomass (g) |
Water content (%) |
Catalpol (% d. wt) |
Scutellarioside (% d. wt) |
Total IGs (% d. wt) |
Scutellarioside/
total IGs |
||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| F | P | F | P | F | P | F | P | F | P | F | P | ||
| Herbivory | 1 | 24·1 | 0·0001 | 21·9 | 0·0001 | 0·11 | 0·74 | 8·54 | 0·004 | 6·14 | 0·015 | 1·72 | 0·19 |
| Age | 2 | 550·9 | 0·0001 | 10·7 | 0·0001 | 11·59 | 0·0001 | 10·24 | 0·0001 | 17·83 | 0·0001 | 5·32 | 0·006 |
| Age × herbivory | 2 | 3·33 | 0·04 | 0·32 | 0·73 | 1·37 | 0·26 | 0·44 | 0·64 | 0·07 | 0·93 | 1·77 | 0·17 |
| Error | 128 | ||||||||||||