Many plants don't take kindly to having their heads chopped off. On the other hand, the grasses don't seem to mind under usual conditions. Herbivores are animals that feed on plants, and they far outnumber carnivores that feed on flesh or omnivores that will eat most anything. Most plants grow from the tips of their branches and, as these tips are destroyed by herbivores, are forced to grow new shoots from buds below the amputations. Continuous hard usage can stunt or even kill the plant.
Under constant attack by grazers, such as bison and horses, grasses
have evolved a somewhat different approach, with several growing points on each shoot.
The most important ones are located near the base of the plant. Clipping off the grass
blades steals sustenance from the plant, but the shoot survives, growing from its base
and quickly producing new leaves. Nevertheless, continuous cropping can allow
insufficient greenery for food production and storage, and feeding to the base can
destroy the growth points. Add drought, and a grassland turns to desert.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.