Upwind Movement of Achenes of Centaurea eriophora L. on the Ground |
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| Authors: | WITZTUM, ALLAN SCHULGASSER, KALMAN VOGEL, STEVEN |
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| Affiliation: | Department of Life Sciences, Ben Gurion University of the Negev, P.O.B. 653, Beer Sheva, Israel Pearlstone Center for Aeronautical Studies, Department of Mechanical Engineering, Ben Gurion University of the Negev, P.O.B. 653, Beer Sheva, Israel Department of Zoology, Duke University, Durham, NC 27708, USA |
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| Abstract: | The lightly compressed achenes of Centaurea eriophora L. beara pappus composed of stiff bristles at their apex and have anelaiosome appendage at their base. The pappus is ineffectivein keeping the achene wind-borne but does serve to regulatethe movement of the achene on the ground in response to wind.In wind the achene swivels like a weather vane with the baseof the achene pointing into the wind. In weak wind the pappusbristles prevent the achene from blowing away. In stronger windthe bristles move due to their flattened, flexible, hinge-likebases and act like ratchets against the substratum, thus enablingthe achene to move upwind. In either case achenes remain ingroups. Ants are attracted to the elaiosome and disperse theachenes. Wind-induced movement was explored by testing acheneson various substrata in a wind tunnel at free-stream speedsbetween 2 and 7 m s-1. Wind dispersal; Centaurea eriophora ; seeds; achenes |
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