16 research outputs found
An in vitro assessment of type, position and incidence of isthmus in human permanent molars
Biological invasion of European tomato crops by Tuta absoluta: ecology, geographic expansion and prospects for biological control
The Effects of Analyses of Contingencies on Clinically Relevant Behaviors and Out-of-session Changes in Functional Analytic Psychotherapy
Stable isotope systematics and fluid inclusion studies in the CuâAu Visconde deposit, CarajĂĄs Mineral Province, Brazil: implications for fluid source generation
Absolute metabolite concentrations and implied enzyme active site occupancy in Escherichia coli
Dynamic effects of price promotions: field evidence, consumer search, and supply-side implications
Ordovician ash geochemistry and the establishment of land plants
<p>Abstract</p> <p>The colonization of the terrestrial environment by land plants transformed the planetary surface and its biota, and shifted the balance of Earthâs biomass from the subsurface towards the surface. However there was a long delay between the formation of palaeosols (soils) on the land surface and the key stage of plant colonization. The record of palaeosols, and their colonization by fungi and lichens extends well back into the Precambrian. While these early soils provided a potential substrate, they were generally leached of nutrients as part of the weathering process. In contrast, volcanic ash falls provide a geochemically favourable substrate that is both nutrient-rich and has high water retention, making them good hosts to land plants. An anomalously extensive system of volcanic arcs generated unprecedented volumes of lava and volcanic ash (tuff) during the Ordovician. The earliest, mid-Ordovician, records of plant spores coincide with these widespread volcanic deposits, suggesting the possibility of a genetic relationship. The ash constituted a global environment of nutrient-laden, water-saturated soil that could be exploited to maximum advantage by the evolving anchoring systems of land plants. The rapid and pervasive inoculation of modern volcanic ash by plant spores, and symbiotic nitrogen-fixing fungi, suggests that the Ordovician ash must have received a substantial load of the earliest spores and their chemistry favoured plant development. In particular, high phosphorus levels in ash were favourable to plant growth. This may have allowed photosynthesizers to diversify and enlarge, and transform the surface of the planet.</p