Indigestibility of C4 Bundle Sheath Cells by the Grasshopper, Melanoplus confusus1,2

Abstract

In a previous study we found that many herbivores, particularly insects, exhibited dramatically decreased fitness on a diet of C4 vegetation. The characteristic leaf morphology of C4 plants, in which the veins are surrounded by thick-walled, organelle-rich bundle sheath cells, suggested a hypothesis to explain this pattern. If the nutrient-rich contents of these cells were unavailable to the herbivores, the nutritive value of C4 vegetation would be dramatically lowered. To test this, we fed two C3 grasses and three C4 grasses to the grasshopper, Melanoplus confusus Scudder. Although this grasshopper was capable of completely breaking down the cells of the C3 grasses, the bundle sheath cells of the C4 grasses passed through its digestive tract largely unbroken, with their contents intact.