A novel mechanism by which silica defends grasses against herbivory.

BACKGROUND AND AIMS Previous studies have shown that silica in grass leaves defends them against small herbivores, which avoid high-silica grasses and digest them less efficiently. This study tested the idea that silica can reduce digestibility by preventing the mechanical breakdown of chlorenchyma cells. METHODS Both the percentage of total chlorophyll liberated from high- and low-silica grass leaves by mechanical grinding and the chlorophyll content of locust faeces were measured. KEY RESULTS High-silica grasses released less chlorophyll after grinding and retained more after passing through the gut of locusts, showing that silica levels correlated with increased mechanical protection. CONCLUSIONS These results suggest that silica may defend grasses at least in part by reducing mechanical breakdown of the leaf, and that mechanical protection of resources in chlorenchyma cells is a novel and potentially important mechanism by which silica protects grasses.