Plant-herbivore interactions : The indigestibility of C₄ bundle sheath cells by grasshoppers

Plants with the C₄ dicarboxylic acid pathway of photosynthetic CO₂ fixation are generally nutritionally inferior to C₃ (Calvin cycle) plants as foodstuff for herbivores. A possible contributing factor to this nutritional inferiority is the concentration, in C₄ plants, of large quantities of nutritional material in very tough, thick-walled vascular bundle sheath cells which herbivores may not be able to break down. Experiments with 10 species of grass-hoppers from different areas in the United States revealed large numbers of unbroken bundle sheath cells, contents intact, in fecal pellets produced when the grasshoppers were fed C₄ vegetation. We conclude that the material stored in C₄ bundle sheath cells is at least partially unavailable to herbivores, and that this may contribute to the observed nutritional inferiority of C₄ vegetation.