A novel mechanism by which silica defends grasses against herbivory

• ackground 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. © The Author 2008. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.