FIGURE 1.

Impacts of CO₂, temperature and aphid presence on dry mass of Medicago sativa when growing in (A) non-supplemented and (B) Si supplemented soil. Mean values ± standard error shown (N = 20) with statistically significant effects indicated ^∗P < 0.05, ^∗∗P < 0.01, and ^∗∗∗P < 0.001. Significant factors for the whole experiment given in the upper panel (see Table 1 for full results) and for Si– and Si+ plants separately in the respective graphical panels.