Variación anatómica del tallo y ultraestructura de la membrana de la punteadura en los elementos traqueales de Selaginella pallescens (Selaginellaceae)

Abstract

<p><strong>Background:</strong> The possible intraspecific anatomical variation in inferior tracheophytes is not recorded. In this study, we describe the anatomical variation of the aerial stems of <em>Selaginella pallescens</em> and the pit membrane (PM).</p><p><strong>Hypothesis:</strong> There is significant structural variation of the aerial stem and PM in a single species in relation to its growth form and habitat.</p><p><strong>Species of study:</strong> <em>Selaginella pallescens </em>(C. Presl) Spring.</p><p><strong>Study site:</strong> State of Mexico, in five localities, September 2016.</p><p><strong>Methods:</strong> Light microscopy, scanning electron and transmission electron microscopy techniques were used to describe the caulinar anatomy and ultrastructure of the PM of <em>S. pallescens</em>. We searched for significant differences in the anatomical attributes by means of analysis of variance of the linear general model, followed by analysis of comparison of means associated to the growth form, substrate and vegetation type of the collection sites.</p><p><strong>Results:</strong> Erect and arrosetate growth form occur in <em>S. pallescens</em>. Anatomically, the cortex varies in the proportion of sclerenchyma. The xylem includes tracheids and vessel elements. The MPs in metaxilema and protoxilema show ultrastructural differences. There are differences in five anatomical variables related to the substrate, the form of growth and the type of vegetation.</p><strong>Conclusions:</strong> <em>Selaginella pallescens</em>has plasticity in growth form, as well as in cortex and vascular tissue as possible response to the environment. The ultrastructure of sieve cells shows characteristics that support taxonomic separation between lycopods and ferns. The differences in PM are interpreted in terms of security in the hydraulic conduction of this species.<p> </p>