Meeting Abstract

S10.3-3  Tuesday, Jan. 7 14:30  Self-burial mechanics of hygroscopically responsive awns JUNG, Wonjong; KIM, Wonjung; KIM, Ho-Young*; Seoul National University; Sogang University; Seoul National University hyk@snu.ac.kr

We present the results of a combined experimental and theoretical investigation of the mechanics of self-burial of some plant seeds whose morphologies respond to humidity change of the surroundings. The seeds of Pelargonium species have hygroscopically active awns that play a critical role in the dispersal from the parent plant and burial in soil. While the awn uncoils in a highly humid condition, it recoils to a helical shape when dry. The rotation is driven by the structure of the cell walls that are comprised of cellulose microfibers aligned in a tilted helix. During uncoiling of the awn, the revolving tail generates thrust to burrow into soil, so that the seed is self-buried. We present the direct observation of the self-burial of the seed while measuring the thrust into a soft substrate simultaneously. The elastica theory allows us to rationalize this botanical digging mechanics using the structural deformations of the hygroexpansive tissues.