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As plants grow, they tend to align their stems and roots along the direction of

ID: 2173919 • Letter: A

Question

As plants grow, they tend to align their stems and roots along the direction of the gravitational field. This tendency, which is related to differential concentrations of plant hormones known as auxins, is referred to as gravitropism. As an illustration of gravitropism, experiments show that seedlings placed in pots on the rim of a rotating turntable do not grow in the vertical direction. Do you expect their stems to tilt inward - toward the axis of rotation - or outward - away from the axis of rotation?

Explanation / Answer

All that's said is that the stems tend to align with the gravitational field, not whether this tends to be parallel or anti-parallel. However, using my knowledge of what plants do, I gather that they align themselves anti-parallel to the field (if a plant is aligned as the vector from the roots towards the head). Thus, on the turntable, I would expect the plants to grow facing inward (rather counter-intuitively). This might be offset by the torquing of the stems by the centrifugal psuedo force, for all I know, but there should be a definite leaning of the plants inward from whatever you'd otherwise expect.