Scanning Electron Microscope Studies on Sphagnum imbricatum

Abstract

In scanning electron microscope studies on the leaves of Sphagnum imbricatum Hornsch. ex Russ. comparisons between untreated and goldcoated material showed the latter preferable for observations. Pore aperture ultrastructural anatomy previously unreported upon is described. The role of differential shrinkage in the rupture of the covering membrane of hyaline cell pores is considered. Evidence for the shrinkage and furrowing of the outer walls of chlorophyllose cells as drying proceeds is also presented. Since Schimper's (1858) comprehensive treatise, comparatively little has been added to our knowledge of Sphagnum gametophyte morphology. Braithwaite (1880) surveyed the important literature to 1876. Durham (1937) studied the development of the branch leaves and the ontogeny of the hyaline cells. The majority of recent work on Sphagnum has been concerned with its taxonomy and ecology (Rigg, 1940, 1951). Relatively few electron microscopical investigations have been published on the gametophytes of the Musci. Paolillo and Reighard (1967) characterized the ultrastructural features of the green lamellae on the adaxial surface of Polytrichum and Atrichum leaves. Apparently there are no comparable studies on Sphagnum gametophytes. The topography of the Sphagnum leaf lends itself particularly well to observation by means of the scanning electron microscope. This is a newly developed research tool, which, so far as the literature is concerned, seems not to have been used on mosses. MATERIALS AND METHODS Mature gametophores of Sphagnum imbricatuum Hornsch. ex Russ. were cultured on peat moss under high humidity conditions in a terrarium exposed to morning sunlight. Voucher specimens were deposited in the cryptogamic herbarium of the University of Nevada. Material 1 The scanning electron microscope used in these studies is located in the Electronics Research Laboratory, University of California, Berkeley. Purchase was supported by NSF grant GB-6428; operation is supported by NIH grant GM-15536 and NSF grant GK-3845. 2 Department of Biology, University of Nevada, Reno, Nevada 89507. 3 Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720. FIGURES 1-4. Sphagnum branch leaves at various magnifications, all gold-coated except those in Figure 1. 1. Uncoated, untreated branch, 70x. 2. Vacuum-evaporated and goldcoated branch, 26x. 3. Enlarged view of one leaf, 65x. 4. Portion of the abaxial leaf surface above the middle, 260X. This content downloaded from 207.46.13.159 on Sat, 22 Oct 2016 04:42:01 UTC All use subject to http://about.jstor.org/terms 1969] MOZINGO ET AL.: SPHAGNUM IMBRICATUM 485