Polevova, S.V., A.V. Moiseenko, M.A. Kolesnikova, D.A. Ashikhmina & M.S. Ignatov. 2019. An attempt to create air sacs in spores? On the unusual spore structure in moss Encalypta longicollis

Arctoa (2019) 28: 171–178

doi: 10.15298/arctoa.28.15

An empty large granules covering spore surface are discovered in Encalypta longicollis, being the first case of the gas-filled structures in moss spores and likely any spores of any Embryophyta. This species is characterized by especially large spores, 55–85(–95) mm in diameter, whereas in other species of the genus spores are 9–40(–50) mm. Many granules on spore surface of E. longicollis develop with age a cavitity in their proximal or middle part. Transmission electron microscopy and tomography show the channels filled with osmiophilous compound leaking either from exine or intine, crossing exine by narrow, inconspicious channels, and then spreading in perine. Channels or broad zones with osmiophilous compound terminate in areas where texture shows series of progressive decomposition, from spongiose to lacunose and finally to cavities, the latter filling up to half of granule volume. The gas-filled space reduces the granule density, facilitating the ability of spores for dispersal by wind or by water currents.