Meeting Abstract
S4.8 Monday, Jan. 4 Floral Trebuchets, Airguns and Elaters Effect Rapid Spore Dispersal in Low Growing Plants EDWARDS, J.*; WHITAKER, D.L.; Williams College; Pomona College joan.edwards@williams.edu
Wind-dispersed spores of ground dwelling plants are small with low terminal velocities so they can be held aloft and carried long distances. The height of spore release determines the distance of dispersal. But spores easily carried by wind are also rapidly decelerated when moving through air. Plants growing close to the ground use extraordinary accelerations to achieve even modest heights. We report three ultra-rapid movements that effect spore dispersal. First floral trebuchets of bunchberry dogwood (Cornus canadensis ) where pollen is launched from anthers through the release of elastic energy stored in the filaments. We use high-speed video (10,000 fps) to show that pollen held between the thecae of adjacent stamens is vertically accelerated up to 24,000± 6,000 m s-2 with speeds of 3.1± m s-1 launching pollen to a mean height of 2.5 cm (range 2.2-2.7 cm; n=5). Outdoors in steady wind pollen is carried over 1m and can effect cross-pollination in this obligate outcrosser. Second the exploding airgun capsules of Sphagnum moss.). Mature capsules form on pseudopodia up to 20 mm above the moss capitula. In sun capsules dehydrate and shrink transversely increasing pressure and explosively popping the cap free from the capsule vertically propelling spores. We used high-speed video (1,000 to 100,000 fps) to show that the exploding capsules of Sphagnum generate vortex rings to achieve launch velocities for the spores of 16.7 m s-1 (mean± s.e.m., N = 13, range 7.9 to 29.8 m s-1, with a lower bound of acceleration of 1.6 x 10 6 m s-2. The spores are propelled to heights of 10.35 ± .64 cm (mean ± s.e.m., N = 10, range 7.39 to 14.35 cm) into the turbulent boundary layer. Third are the elaters attached to (Equisetum hyemale ) spores and elaters mixed with the spores of (Preissia quadrata ) which effect spore dispersal by moving rapidly in response to changes in humidity.
