Wheat
In the wild, the awns of emmer wheat spikelets help them dig into the soil.  With humidity in the night, the awns of the spikelet become erect and draw together, and in the process push the grain into the soil.  During the day, the humidity drops and the awns slacken back again.  During the course of days and nights, the awns' pumping movements drill the spikelet as much as an inch into the soil.