Origami plant action

The sophisticated origami-like unfolding mechanism of ice plant seed capsules is revealed in Nature Communications this week. The findings could potentially lead to new design principles for the engineering of satellites and artificial muscles.

The Aizoaceae — which have many species known as ice plants — have evolved adaptations which allow them to prosper in environments with scarce water resources. Central to their success is a distinctive seed dispersal mechanism in which protective valves on seed capsules mechanically open when sufficiently hydrated with liquid water. Matthew Harrington and co-workers investigate the unfolding mechanism of the desert ice plant seed capsule and find that the reversible hydration-dependent unfolding occurs via a cooperative flexing-and-packing mechanism that is mediated by swellable cellulose layers.

They conclude that plant movements that do not depend on cellular activity, as seen in desert ice plants, can provide inspiration for the design of ‘programmable matter’ that changes shape in response to external stimuli.