Walking Seeds of Wild Oats

The seed dispersal unit of plants such as wild oats carries two elongated stiff awns (arm like outgrowths) covered by unidirectional silica hairs. The awns bend and twist with changes in humidity, pushing the seed capsule along and into the ground.

The two arms, called sister awns, attached to the same seed capsule, intersect twice during a fixed time interval, which differs for different plants. Once the awns cross each other, the silica hairs lock themselves to prevent any subsequent movements, causing the burial of the seeds.

The time of intelocking is also different for different plants. Sudden release of the interlocked awns in some plants cause the dispersal unit to jump and change its direction before settling down.