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Science  23 Jul 2010:
Vol. 329, Issue 5990, pp. 395-396
DOI: 10.1126/science.1193047

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Most mosses, including peat mosses of the genus Sphagnum (about 285 species), disperse their spores by turbulent wind (1). In still air, spores (22 to 45 µm in size) sink at only 0.5 to 2 cm/s, ideal for wind dispersal (2). However, spore capsules, positioned on a short stalk, grow to heights of about 1 cm and do not extend into the atmospheric turbulent boundary layer (more than 10 cm above ground). Peat mosses solve this problem with an “air gun” mechanism that explosively discharges spores from a pressurized cylindrical capsule µ2 mm in length (see the figure), projecting spores over 10 to 20 cm (13). On page 406 of this issue, Whitaker and Edwards (4) report that an upward-traveling turbulent vortex ring of spores and air is formed by this explosion within less than 0.2 ms, carrying sufficient momentum to reach the turbulent boundary layer.