Horsetail spores don't need legs to jump

Sophia Li

Author: Susan Milius
Published: September 10, 2013
https://www.sciencenews.org/article/horsetail-spores-dont-need-legs-jump

Summary
Although they lack legs, the spores of spiky horsetail plants can jump about 200 times their body length. Equisetum (horsetail) spores are spherical bodies with four flexible arms called elaters. Elaters are long, double-layered ribbons that wrap around the main body of each spore. These elaters uncurl when the air humidity lowers, nudging the spore along in a small "walking step." Physicist Philippe Marmottant of the University of Grenoble in France noticed that these spores make speedy leaps after being soaked. When the elaters dry out, they can uncurl very quickly and launch the micro spores into jump about as high as a centimeter- often carrying them to a new home. Once the humidity rises again, the elaters curl up back up, preparing to make another jump when they dry out. According to Marmottant, uncurling begins when humidity drops below about 75 percent. The direction in which the spore moves, or whether it will "walk"or "jump" is unpredictable. Horsetail spores sometimes clump as well. These clumps move faster than individual spores, as they have more elaters facing outwards than individual spores. Elaters are unique to horsetail spores. These spores in motion have inspired Marmottant and his colleagues to develop a robot that moves like a horsetail spore, although they do not yet know what they will do with it. 

Connection
This article relates to our study of plants and spores. As a part of our study of plants, we learned about the different kinds of plants, including pteridophytes. This article discusses horsetails, which are pteridophytes that grow in marshy, sandy areas. We also learned in this unit how many plants, such as pteridophytes, use spores as a means of reproduction. Previously in this term, we learned that spores are used in fungal reproduction as well. Many spores are dispersed through the wind, while others are flagellated and can swim through water. Horsetail spores are dispersed in yet another method, as they use elaters to propel them to new locations.