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Aeroterrestrial Coleochaete (Streptophyta, Coleochaetales) models early plant adaptation to land
Author(s) -
Graham Linda E.,
ArancibiaAvila Patricia,
Taylor Wilson A.,
Strother Paul K.,
Cook Martha E.
Publication year - 2012
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.1100245
Subject(s) - biology , subaerial , desiccation , algae , botany , rhagoletis , ecology , paleontology , pest analysis , tephritidae
• Premise of the study: The streptophyte water‐to‐land transition was a pivotal, but poorly understood event in Earth history. While some early‐diverging modern streptophyte algae are aeroterrestrial (living in subaerial habitats), aeroterrestrial survival had not been tested for Coleochaete , widely regarded as obligately aquatic and one of the extant green algal genera most closely related to embryophytes. This relationship motivated a comparison of aeroterrestrial Coleochaete to lower Paleozoic microfossils whose relationships have been uncertain. • Methods: We tested the ability of two species of the experimentally tractable, complex streptophyte algal genus Coleochaete Bréb. to (1) grow and reproduce when cultivated under conditions that mimic humid subaerial habitats, (2) survive desiccation for some period of time, and (3) produce degradation‐resistant remains comparable to enigmatic Cambrian microfossils. • Key results: When grown on mineral agar media or on quartz sand, both species displayed bodies structurally distinct from those expressed in aquatic habitats. Aeroterrestrial Coleochaete occurred as hairless, multistratose, hemispherical bodies having unistratose lobes or irregular clusters of cells with thick, layered, and chemically resistant walls that resemble certain enigmatic lower Paleozoic microfossils. Whether grown under humid conditions or air‐dried for a week, then exposed to liquid water, aeroterrestrial Coleochaete produced typical asexual zoospores and germlings. Cells that had been air‐dried for periods up to several months maintained their integrity and green pigmentation. • Conclusions: Features of modern aeroterrestrial Coleochaete suggest that ancient complex streptophyte algae could grow and reproduce in moist subaerial habitats, persist through periods of desiccation, and leave behind distinctive microfossil remains.

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