Fig. 3 Percent inhibition is a measure of trypsin protease
inhibitor activity, with high inhibition indicating high levels of
protease inhibitor activity. Tomato plants grown without mycorrhizae
induced protease inhibitors strongly, while plants grown with
mycorrhizae did not show significant induction. Symbols represent mean
+/- SE.
Since mycorrhizae and competition interacted to affect leaf consumption
and affected both plant nutritional content and resistance traits, we
tested which traits quantitatively correlated with leaf damage. Cabbage
loopers consumed less leaf tissue when C/N ratios were high
(F1,31=6.99, p=0.013). While we saw a similar effect
with nitrogen alone (F1,35=5.50, p=0.025), the C/N ratio
explained a higher proportion of the variation
(R2=0.16). While treatments with high protease
inhibitors also had low cabbage looper leaf consumption, neither
constitutive or induced protease inhibitor levels correlated with either
cabbage looper feeding or mass gain (F1,29=0.781,
p=0.383, F1,34=0.365, p=0.550).