The Origin and Early Evolution of Roots

Abstract

Geological sites of exceptional fossil preservation are becoming a focus of research on root evolution because they retain edaphic and ecological context, and the remains of plant soft tissues are preserved in some. New information is emerging on the origins of rooting systems, their interactions with fungi, and their nature and diversity in the earliest forest ecosystems. Remarkably wellpreserved fossils prove that mycorrhizal symbionts were diverse in simple rhizoid-based systems. Roots evolved in a piecemeal fashion and independently in several major clades through the Devonian Period (416 to 360 million years ago), rapidly extending functionality and complexity. Evidence from extinct arborescent clades indicates that polar auxin transport was recruited independently in several to regulate wood and root development. The broader impact of root evolution on the geochemical carbon cycle is a developing area and one in which the interests of the plant physiologist intersect with those of the geochemist.

Belowground rhizomes in paleosols: The hidden half of an Early Devonian vascular plant

“…Rhizomatous habit also occurred in the Early Devonian rhyniopsids (21,22), early euphyllophytes, and other groups (14). Most Rhynie Chert plants of Early Devonian age have rhizoid-based rhizomatous axes, which are either surficial or shallowly subterranean at a millimeter-scale depth (22,23). Large woody rhizomes of aneurophytalean progymnosperms have been found in the Middle Devonian of New York, alongside cladoxylopsid and lycopsid trees (7).…”

“…Although the small aboveground size could suggest that the belowground components of these plants were similarly small and therefore limited in their impact on sediments, fossils of their belowground structures such as roots or rhizomes are rare and incomplete (16)(17)(18)(19)(20)(21)(22)(23). Some species have been recorded as bearing shallow rooting systems (or root-like structures) (16)(17)(18)(19)(20), others as having surficial or shallowly subterranean rhizomatous axes with rhizoids (21)(22)(23). Thus, the geochemical effect of these plants on the substrate (or soils) was presumably limited (11), and their capacity for landscape stabilization was trivial.…”

Conserved Gene Expression Programs in Developing Roots from Diverse Plants

“…This transition was associated with numerous physiological and developmental innovations in plants, including in some lineages, the evolution of an exploratory multicellular subterranean organ (the root) suited for effective water and nutrient acquisition and plant anchorage. Considering the fossil record and root morphology in extant plants, it is generally accepted that roots evolved independently on more than one occasion during vascular plant evolution (Kenrick and Crane, 1997;Raven and Edwards, 2001;Friedman et al, 2004;Kenrick and Strullu-Derrien, 2014).…”

Focus on Roots

“…It was the evolution of roots driven by selection for resource acquisition from proto soils that allowed plants to colonize the land. Kenrick and Strullu-Derrien (2014) provide a fascinating glimpse into this process by reviewing what the fossil record tells us. Kenrick and Strullu-Derrien (2014) close with a discussion of how, amazingly, the evolution of roots has affected the Earth's geochemical cycle.…”

“…Kenrick and Strullu-Derrien (2014) provide a fascinating glimpse into this process by reviewing what the fossil record tells us. Kenrick and Strullu-Derrien (2014) close with a discussion of how, amazingly, the evolution of roots has affected the Earth's geochemical cycle. This is a fitting reminder of the critical importance of plant roots, an organ that can easily be overlooked as it buries itself out of sight into the soil.…”