Developmental and Structural Section
Graham, Linda E. , Arancibia-Avila, Patricia .
Terrestrial Coleochaete orbicularis (Charophyceae, Streptophyta).
A terrarium was planted with typical thalli of Coleochaete orbicularis that had been grown in SD11 liquid medium, then loosely covered with a glass plate and maintained for 16 months, to simulate an early terrestrial plant community. Coleochaete was dispersed onto a thin layer of quartz sand--known to have been abundant along fluvial channels and lacustrine margins in Precambrian through Ordovician times--above a thin layer of loam soil. The system received occasional "precipitation" in the form of distillled water, and on one occasion, SD11 medium, to mimic a nutrient-enriching flood event. Two hornworts were also planted, and a moss and a fern, as well as cyanobacteria, and other microalgae appeared in the system over time. Terrestrial C. orbicularis formed thick, macroscopic lumps with unistratose lobes. Vegetative cells had thick cell walls that were autofluorescent in V and UV excitation (not typical of such aquatic-grown cells). Hairs were absent. Terrestrial-grown Coleochaete thalli that had been removed to a water drop on a slide and observed over the course of a week released many zoospores whose morphology and behavior were typical of Coleochaete. These settled and developed into few-celled, flat germlings whose morphology is unique to Coleochaete, and whose cell walls were not autofluorescent. Similar germlings and empty zoosporangia were visible on the surfaces of sand grains from the terrarium. This experiment revealed that Coleochaete is able to adapt to terrestrial conditions similar to those likely present prior to the rise of vascular plants, and can grow and reproduce on terrestrial substrates when some moisture is present.
1 - University of Wisconsin-Madison, Botany, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
2 - University del Bio-Bio, Ciencias Basicas, Chillan, , Chile
Presentation Type: Paper
Location: Alpine A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 3:30 PM