EVIDENCE OF CIRCUMNUTATIONAL GROWTH MOVEMENTS OF RHIZOMES OF POA PRATENSIS L. THAT AID IN SOIL PENETRATION

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Abstract
The growth of rhizomes of Poa pratensis L. through dense soil was studied by means of an apparatus consisting of a short, pivoted, balance arm having, at one end, a cone into which a rhizome tip was guided, and at the other end, an inclined mirror onto which a collimated light beam was directed, the reflection being projected onto the distant wall of a darkened room.At 1000 × magnification a circular, clockwise, 24 hour rotation of the rhizome tip was observed. The actual diameter of revolution was between 0.5 and 3.0 mm.At 1000 × magnification a minor, circular, clockwise, revolution of 1 to 2 hours period, superimposed on the major revolution was determined. The actual diameter of revolution was between 0.001 and 0.010 mm.The major and minor revolutions were circumnutational movement rather than torsional twisting. The region of both movements was the ultimate 2 to 3 cm of the rhizome. Both the ultimate cataphyll and the true rhizome stem were involved.These rotational movements undoubtedly aid the rhizome in penetration of the soil.

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