Centrifuges: evolution of their uses in plant gravitational biology and new directions for research on the ground and in spaceflight.

The use of centrifugation as a tool for exploring qualitative and quantitative features of plant responses to gravity and to other body forces can be traced to plant scientists' early 19th century experiments. To study how plants perceive and respond to gravitational stimuli requires experimental manipulation of the force or acceleration vector direction and magnitude. As technology advanced, especially during the past half-century, so did the sophistication of experimental designs and of the scientific questions that could be addressed. The most significant improvement in methodology probably will prove to be attainment of experimental access to the hypogravity range of inertial accelerations by the combination of centrifugation and spaceflight.