Circumnutation:
Nutation refers to the bending movements of stems, roots, leaves and other plant organs caused by differences in growth in different parts of the organ. Circumnutation refers specifically to the circular movements often exhibited by the tips of growing plant stems, caused by repeating cycles of differences in growth around the sides of the elongating stem. Nutational movements are usually distinguished from ‘variational’ movements caused by temporary differences in the water pressure inside plant cells (turgor). [Wikipedia]
That’s a new one on me. Noted in “The surprising way sunflowers work together to get enough light,” Leah Crane, NewScientist (24 August 2024, paywall):
Sunflowers move in a way that helps their neighbours. The seemingly random motion of the plants’ roots and shoots actually minimises shade cover in crowded environments, ensuring that all of them get enough light to grow.
Scientists have known about this plant motion, known as circumnutation, for centuries, but its purpose has always been elusive. “In climbing plants, it’s clear that it’s a search process, searching for a new stick to twine on. But in other plants, it’s not clear if it’s a bug or a feature,” says Yasmine Meroz at Tel Aviv University in Israel.
