On dislodging caryopses of wild oats

The untwisting movement of the hygroscopic awn of wild oats (Avena fatua L.) causes the caryopses to rotate in anticlockwise direction and to dislodge from the spikelet. While untwisting, the awn generates more torque than is required to separate the caryopsis. The periodic shattering of caryopses caused by awn movement may be biologically significant in that the chances of having favorable moisture conditions for caryopses germination in the field at the time of dispersal are increased. Financial support by the Saskatchewan Research Council is gratefully acknowledged.