BOSTON — Plants appear to live the ultimate sedentary lifestyle, but they’ve got mad aeronautical skills when it comes to their progeny. Two new studies — one investigating the catapult action of ferns, and another examining the “jumping spores” of a species of horsetail — reveal surprising botanical mechanical tricks for dispersing future offspring.
Consider Equisetum’s jumping spores. Known as horsetail or scouring rush, Equisetum bears spores that are decked out with four slender, arm-like projections called elaters. Botanists have long presumed that the elaters, which are curled around the spore and unfurl as local humidity drops, give the spores lift, akin to the tail or wings of a kite. But new research suggests that before the spores go airborne, the elaters provide a sticky friction that helps launch the spores aloft.
The spores are a mere 50 micrometers across. At that size, adhesion forces dominate, making small things — like the spore itself — stick to surfaces. But once the elaters have unfurled, the slender arms can provide some alternative grip. When the elastic energy stored by the elaters is released, the spores launch, jumping several times their height, physicist Philippe Marmottant explained March 1 at a meeting of the American Physical Society.