A seed that twists its way into soil

Grass awn movement

How can a grass seed move itself? Cooke describes a cultivated grass whose long awn responds to moisture. 🌱

Grass awn movement

Moisture loosens the lower twisted awn. As it untwists, it turns the feathery upper part. 💧

Grass awn movement

Then the awn dries and twists again. Cooke explained this by unequal moisture changes in porous, spongy and harder, close-textured parts.

Grass awn movement

That repeated unwind-and-twist helps drive the seed’s sharp point into soil, covering the seed. Moisture turns the awn into a seed-moving mechanism. 🌾

A seed that twists its way into soil

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