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No. 35: Sep-Oct 1984

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Gravity And Going Around In Ellipses

We thought that our readers might like to know that the force of gravity apparently has no significant effect on circumnutation. Now circumnutation is the result of an "impressively ubiquitous mechanism" in all elongating plant organs. More simply, it is the elliptical weaving motion seen in the tips of growing leaves, shoots, flower stalks, branch roots, etc. In a 4- to 5-day-old sunflower seedling, the ellipse traced is 6-8 millimeters long and takes about 110 minutes. The ellipses result from differ-ential growth in the elongating plants. No one knew whether the force of gravity played a role in circumnutation until some sunflower seedlings were flown on Spacelab 1. Zero-g did not affect circumnutation at all.

(Brown, Allan H. and Chapman, David K.; "Circumnutation Observed without Significant Gravitational Force in Spaceflight," Science, 225:230, 1984.)

Comment. Nature seldom indulges in frivolous actions, but we just may have a phenomenon here that has absolutely no deeper significance.

From Science Frontiers #35, SEP-OCT 1984. 1984-2000 William R. Corliss