01741nas a2200205   4500008004100000245010200041210006900143260001200212300001200224490000700236520105300243653001301296653001401309653002601323100001801349700001801367700001501385700001801400856011701418       2012                        eng d00aDevelopment of megaspores and microspores in Isoetes japonica A. Br. (Lycopodiophyta: Isoetaceae)0 aDevelopment of megaspores and microspores in Isoetes japonica A   c2012///  a84 - 960 v513 aMicrospore and megaspore development in Isoetes japonica was studied using light, scanning electron and transmission electron microscopy. Differences in cytokinesis following meiosis result in monolete microspores with bilateral symmetry, and trilete megaspores with radial symmetry. Wall development follows essentially the same sequence in both microspores and megaspores, but with the wall of the latter being very much thicker. A significant difference was observed in the tetrad stage, when microspores have an essentially rounded outline with the plasma membrane folded into a crest at the site of the future aperture. Megaspores in the tetrad stage are strongly invaginated over their entire surface, creating numerous crests, and this appears to have a role in determining the morphology of the perispore. The outline shape of the megaspore perispore having been established in the tetrad stage, most of its substance is added later and is derived from the degenerating tapetum. © 2012 Copyright 2012 Collegium Palynologicum Scandinavicum.10aexospore10aperispore10asporoderm development1 aBlackmore, S.1 aTakahashi, M.1 aUehara, K.1 aWortley, A.H.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-84863571691&partnerID=40&md5=f7e81951aa6adcdbb44db83d38c686dd