Abstract Detail

Developmental and Structural Section

Bachelier, Julien [1], Razik, Imran [2], Sanchez, Fior [2], Seago, James L. [3].

The root of Austrobaileya scandens (Austrobaileyaceae) and its implications for the evolution of root structure and development in seed plants.

Previous comparative studies of root structure and development in diverse lineages of gymnospermous and angiospermous seed plants demonstrated that the root apical meristems (RAM) and tissues of Gymnosperms share many features with some woody early-diverging and basal extant lineages of flowering plants. However, these studies revealed that these similarities are not as marked in the early-diverging lineages Amborella and Austrobaileyales, as they are in the basal (or more derived) Magnoliids. In addition, these studies showed that the RAMs of Amborella and Austrobaileyales can share some features with other basal or more derived lineages, and that those of Nymphaeales, a woodless lineage which also diverged before the Magnoliids, are very distinct if not unique. In this study, we used a combination of microtome sections and bright field, confocal, and scanning electron microscopy to re-evaluate the RAM and root tissue differentiation in some of these early-diverging lineages of flowering plants studied previously, as well as in Austrobaileya scandens, a monotypic genus of woody lianas sister to all other Austrobaileyales. Our preliminary results indicate that the structure of the young roots of A. scandens is relatively simple. The epidermis lacks root hairs and the stele typically is diarch with two poles of protoxylem and protophloem, each with multiple elements. The stele has a central plate and is surrounded by a cortex differentiated into a uniseriate endodermis, a middle region sometimes colonized by arbuscular mycorrhizal fungi, and a multiseriate exodermis. Both the endodermis and exodermis have Casparian bands and suberin lamellae, although suberin lamellae develop later in the endodermis than in the exodermis. In addition, the exodermis shows some radial patterning, which is to be expected since it is multiseriate, but like other roots with an open apical meristem and common initials, there is a typical lack of radial organization in the cortex and outer stele and between the epidermis and exodermis. The structure of the RAM and tissues of A. scandens is thus most similar to those described previously in Amborella and Illicium, and suggests that the first woody flowering plants likely had an open meristem with common initials. However, the significance of the presence of common initials in RAM of woody early-diverging and basal lineages of flowering plants and in Gymnosperms remains unclear.

1 - State University of New York – SUNY Oswego, 30 Centennial Drive, Oswego, NY, 13126, United States
2 - State University of New York – SUNY Oswego, Biological Sciences, 30 Centennial Drive, Oswego, NY, 13126, USA
3 - State University Of New York At Oswego, Professor Emeritus, P O Box 316, Minetto, NY, 13115, USA

Keywords:
root morphology
root anatomy
root apical meristem
common initials
Casparian bands
mycorrhizae
flowering plants
ANITA grade
seed plants.

Presentation Type: Oral Paper:Papers for Sections
Session: 76
Location: Salon 11/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 4:15 PM
Number: 76003
Abstract ID:1273
Candidate for Awards:None