Borisovskaya, Galina M. , Romanova, Marina .
Diversity in fern steles: no more than nodal diversity?.
Delineating plant taxa of higher ranks, stelar type is an important character in phylogeny. Study of stelar development in Gymnocarpium dryopteris, Phegopteris connectilis, Athyrium filix-femina, Matteuccia struthiopteris, Pteridium aquilinum and Dryopteris carthusiana has confirmed the viewpoint that vascular differentiation in ferns is fundamentally different from that in seed plants. The pith and the vascular tissues in all these ferns develop from the shoot apical meristem (SAM) autonomously; origin of the leaves is associated with differentiation of leaf gaps, which influences the pattern of stelar tissue arrangement. The supposed “bicyclical stele” of P. aquilinum is in fact a dictyostele. It consists of two internal meristeles separated by two leaf gaps, in accordance with decussate phyllotaxis. The external cylinder of vascular tissues is composed of numerous vascular bundles of the multibundle leaf traces (LTs). The complexity of M. struthiopteris and D. carthusiana vasculature results from continuously overlapping nodes and multibundle LTs, which together with the meristeles are defined as a perforated dictyostele. Regardless of the number of LTs, the node is unilacunar. At the node, stelar vascular tissues connect with both leaf and root traces. The number of roots in each phytomer usually equals the number of LT bundles; one root located on the lower border of the leaf gap originates in the SAM simultaneously with the leaf. Factors connected with ontogenetic changes of stelar type were studied in A. filix-femina and D. carthusiana. Sporelings with non-zonal SAM organization are protostelic; pith originates simultaneously with the origin of the zone of subsurface initials. The origin of the leaf gap is correlated with the increase in leaf size. Stelar development in all species examined has the same histogenic pattern; differences in stelar morphology are determined by the SAM volume, node/internode length ratio, LT structure and the route of LT connection with the dictyostele.
1 - University of California, Davis, Agronomy and Range Science, One Shields Avenue, Davis, California, 95616-8515, US
2 - St-Petersburg State University, Department of Botany, Universitetskaya nab. 7/9, St-Petersburg, 190034, Russia
shoot apical meristem.
Presentation Type: Poster
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM