Anatomically Preserved Glossopteris Stems with Attached Leaves from the Central Transantarctic Mountains, Antarctica

Abstract

Stems and buds of Glossopteris skaarensis Pigg and buds of G. schopfii Pigg from the Permian Skaar Ridge locality in the central Transantarctic Mountains, Antarctica demonstrate the first anatomically preserved glossopterids known with stem/ leaf attachment. Stems of G. skaarensis are 1-12 mm in diameter (X = 3.1 mm) with a broad pith, poorly defined primary xylem, and a zone of secondary xylem up to 6 mm thick. Pycnoxylic wood conforming to Araucarioxylon Kraus is composed of tracheids with uni-to biseriate oval to hexagonal bordered pits on radial walls, uniseriate rays one to ;{tew cells high, and cupressoid to taxodioid cross-field pitting. Stems have a narrow zone of secondary phloem, aerenchymatous cortex with scattered sclereids, and sometimes a narrow periderm. Two wedge-shaped leaf traces each bifurcate to form four strands in the base of each petiole. Small axillary branches are vascularized by double branch traces that fuse at the margin of the main axis. Buds of G. skaarensis have leaves with narrow lateral laminae and a thickened midrib containing a wide lacuna, delicate vascular strands, and a prominent hypodermis. In contrast, buds of G. schopfii have uniformly thick leaves with prominent, circular vascular bundle sheaths. These anatomical details are used to reconstruct individual types ofglossopterid plants, providing new information toward understanding the ecology and evolution of this important group of Permian seed plants.

Mycorrhizal symbiosis in the Paleozoic seed fern Glossopteris from Antarctica

“…Young Vertebraria rootlets are distinguished by the presence of an intact cortical layer and lack of secondary xylem (Neish et al, 1993;Decombeix et al, 2009). Although the vegetative and some of the reproductive organs of the Glossopteridales from Antarctica have been described (e.g., Taylor et al, 1989b;Pigg and Taylor, 1993;Ryberg, 2009;Ryberg et al, 2012), the fungal associations with these plants have not been studied in great detail (see below).…”

Permian polar forests: deciduousness and environmental variation

“…The occurrence of leaf-rich sedimentary layers has been used to invoke a seasonally deciduous habit for Glossopteris (Plumstead, 1958;Retallack, 1980;Taylor et al, 1992). Pigg & Taylor (1993) observed that Glossopteris leaf compressions vary little in leaf size and suggest that this may reflect periodic leaf drop owing to environmental stresses similar to the habit of evergreen trees and that more evidence is required to link these leaf compression layers with seasonal conditions that would indicate a deciduous habit for Glossopteris. Evergreen trees and deciduous trees, however, exhibit distinct patterns in carbon isotope ratios within tree rings (Schubert & Jahren, 2011).…”

“…At least three wood morphogenera have been described from the study region: Araucarioxylon, Kaokoxylon, and Australoxylon (Pigg & Taylor, 1993;Decombeix et al, 2010Decombeix et al, , 2012; therefore, it is possible that tree height differences are related to species differences in the region. As each wood morphogenera has been found among Glossopteris leaf fossils, however, it is difficult to assess the impact of these different wood morphogenera on the paleoecology of the forests.…”

Bark Anatomy of Late Permian Glossopterid Trees From Antarctica

“…the dead tissues of the outer bark protect the functioning part of the secondary phloem and the vascular cambium against biotic and abiotic hazards. A small amount of preserved secondary phloem was reported in the stem Glossopteris skaarensis (Pigg & taylor 1993) and in Vertebraria roots from Skaar Ridge (Decombeix et al 2009). However, in both cases only a few layers of the tissue were present and the composition and organization of the tissue were unclear.…”