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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A much warmer Earth surface for most of geologic time: implications to biotic weathering

The authors present two scenarios for the temperature history of Earth. One scenario is conventional, the other relies on a warmer history. Both scenarios include surface cooling determined by the evolution of the biosphere and are similar until the Proterozoic period. The warmer scenario requires a higher plant/lichen terrestrial biota to increase weathering intensity. Justification for a warmer surface includes period temperatures from the oxygen isotope record of coexisting phosphates and cherts, an upper limit of 58 degrees C from primary gypsum precipitation, and the lack of fractionation of sulfur isotopes between sulfide and sulfates in Archean sediments.

NASA Discipline Exobiology↗
NASA NTRS1991

Evolutionary dynamics of plants and animals: a comparative approach

Patterns of longevity and rate of appearance of taxa in the fossil record indicate a different evolutionary dynamic between land plants and marine invertebrates. Among marine invertebrates, rates of taxonomic turnover declined through the Phanerozoic, with increasingly extinction-resistant, long-lived, clades coming to dominate. Among terrestrial vascular plants, rates of turnover increased through the Phanerozoic, with short-lived, extinction-prone clades coming to dominate from the Devonian to the present. Terrestrial vertebrates appear to approximate the marine invertebrate pattern more closely than the plant record. We identify two features which individually or jointly may have influenced this distinction. First, land plants continuously invaded stressful environments during their evolution, while marine invertebrates and terrestrial vertebrates did not. Second, the relative structural simplicity and indeterminate mode of plant growth vs. the relative structural complexity and determinate mode of animal growth may have influenced the timing of major clade origin in the two groups.

Review↗
NASA NTRS1996

Growth and photosynthetic responses of wheat plants grown in space

Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment.

NASA Discipline Plant Biology↗
NASA NTRS1994

P-MASS and P-GBA: Two new hardware developments for growing plants in space

Plant growth, and especially plant performance experiments in microgravity are limited by the currently available plant growth facilities (low light levels, inadequate nutrient delivery and atmosphere conditioning systems, insufficient science instrumentation, infrequent flight opportunities). In addition, mission durations of 10 to 14 days aboard the NSTS Space Shuttle allow for only brief periods of microgravity exposure with respect to the life cycle of a plant. Based on seed germination experiments, using the Generic BioProcessing Apparatus hardware (GBA), two new payloads have been designed specifically for plant growth. These payloads provide new opportunities for plant gravitational and space biology research and emphasize the investigation of plant performance (photosynthesis, biomass accumulations) in microgravity. The Plant-Module for Autonomous Space Support (P-MASS) was designed to utilize microgravity exposure times in excess of 30 days on the first flight of the recoverable COMET satellite (Commercial Experiment Transporter). The Plant-Generic Bioprocessing Apparatus (P-GBA), is designed for the National Space Transportation System (NSTS) Space Shuttle middeck and the SPACEHAB environment. The P-GBA is an evolution from the GBA hardware and P-MASS (plant chamber and instrumentation). The available light levels of both payloads more than double currently available capabilities.

Hoehn, Alexander↗
NASA NTRS1984

Origin and Evolution of the Uranian and Neptunian Satellites: Some Dynamical Considerations

The satellite system of Neptune is so irregular that some formation mechanism or subsequent dynamical evolution that sets it apart from the other, more regular, satellite systems is obviously indicated. McKinnon argued that satellite capture is the most likely possibility and has shown that tidal circularization of Triton's presumably highly eccentric initial orbit probably resulted in melting of the satellite's interior. The satellite system of Uranus, although somewhat bland, also has a number of special features that indicate an interesting dynamical history. These include the anomalously high orbital inclination of Miranda and the probable coexistence of small satellites and narrow rings inside the plant's Roche limit. The possibility that orbital evolution due to tidal dissipation is involved in both of these phenomena is discussed. Other topics discussed are: the origin of rings; the formation of coorbital satellites; the lack of stable orbit-orbit resonances in the Uranian satellite system; and chaos, tidal heating and the shapes of Miranda and Ariel.

Dermott, S. F.↗
NASA NTRS1998

Chimeric calcium/calmodulin-dependent protein kinase in tobacco: differential regulation by calmodulin isoforms

cDNA clones of chimeric Ca2+/calmodulin-dependent protein kinase (CCaMK) from tobacco (TCCaMK-1 and TCCaMK-2) were isolated and characterized. The polypeptides encoded by TCCaMK-1 and TCCaMK-2 have 15 different amino acid substitutions, yet they both contain a total of 517 amino acids. Northern analysis revealed that CCaMK is expressed in a stage-specific manner during anther development. Messenger RNA was detected when tobacco bud sizes were between 0.5 cm and 1.0 cm. The appearance of mRNA coincided with meiosis and became undetectable at later stages of anther development. The reverse polymerase chain reaction (RT-PCR) amplification assay using isoform-specific primers showed that both of the CCaMK mRNAs were expressed in anther with similar expression patterns. The CCaMK protein expressed in Escherichia coli showed Ca2+-dependent autophosphorylation and Ca2+/calmodulin-dependent substrate phosphorylation. Calmodulin isoforms (PCM1 and PCM6) had differential effects on the regulation of autophosphorylation and substrate phosphorylation of tobacco CCaMK, but not lily CCaMK. The evolutionary tree of plant serine/threonine protein kinases revealed that calmodulin-dependent kinases form one subgroup that is distinctly different from Ca2+-dependent protein kinases (CDPKs) and other serine/threonine kinases in plants.

NASA Discipline Plant Biology↗
NASA NTRS1992

Biodiversity: molecular biological domains, symbiosis and kingdom origins

The number of extant species of organisms is estimated to be from fewer than 3 to more than 30 x 10(6) (May, 1992). Molecular biology, comparative genetics and ultrastructural analyses provide new insights into evolutionary relationships between these species, including increasingly precise ideas of how species and higher taxa have evolved from common ancestors. Accumulation of random mutations and large macromolecular sequence change in all organisms since the Proterozoic Eon has been importantly supplemented by acquisition of inherited genomes ('symbiogenesis'). Karyotypic alterations (polyploidization and karyotypic fissioning) have been added to these other mechanisms of species origin in plants and animals during the Phanerozoic Eon. The new evolution concepts (coupled with current rapid rates of species extinction and ignorance of the extent of biodiversity) prompted this analysis of the field of systematic biology and its role in the reorganization of extant species into higher taxa. Two superkingdoms (= Domains: Prokaryotae and Eukaryotae) and five kingdoms (Monera = Procaryotae or Bacteria; Protoctista: algae, amoebae, ciliates, foraminifera, oomycetes, slime molds, etc.; Mychota: 'true' fungi; Plantae: one phylum (division) of bryophytes and nine phyla of tracheophytes; and Animalia) are recognized. Two subkingdoms comprise the monera: the great diverse lineages are Archaebacteria and Eubacteria. The criteria for classification using molecular, ultrastructural and genetic data for this scheme are mentioned. For the first time since the nineteenth century, logical, technical definitions for each group are given with their time of appearance as inferred from the fossil record in the primary scientific literature. This classification scheme, which most closely reflects the evolutionary history, molecular biology, genetics and ultrastructure of extant life, requires changes in social organization of biologists, many of whom as botanists and zoologists, still behave as if there were only two important kingdoms (plants and animals).

Non-NASA Center↗
NASA NTRS1999

Transposable elements as a molecular evolutionary force

This essay addresses the paradoxes of the complex and highly redundant genomes. The central theses developed are that: (1) the distinctive feature of complex genomes is the existence of epigenetic mechanisms that permit extremely high levels of both tandem and dispersed redundancy; (2) the special contribution of transposable elements is to modularize the genome; and (3) the labilizing forces of recombination and transposition are just barely contained, giving a dynamic genetic system of ever increasing complexity that verges on the chaotic.

Review↗
NASA NTRSDate not supplied

Long -Term Architecture Development For The Moon And M

Developing an enterprise-level architecture encompassing future human-robotic science and exploration at the Moon and Mars requires a visionary approach that ensures NASA is responsive to national priorities and global science and technology advancement objectives. While the initial capabilities needed to return humans to the Moon may be well understood, NASA is still formulating a long-term infrastructure at the Moon and working to narrow the trade space for the first human missions to Mars. This paper will focus on the formulation and current status of engineering and design applications for a long-term and robust lunar architecture that will implement the Artemis Base Camp concept, including pre-formulation activities and elements currently in formulation. Authors will demonstrate how the Moon-to-Mars campaign approach fosters commonality of requirements and standards across individual mission elements, as well as multi-destination systems and operations, to reduce risk and encourage healthy competition in the growing space market. Among the Artemis Base Camp elements discussed will be multiple surface mobility elements, a fixed, anchoring surface habitat, fission surface power, and an in-situ resource development pilot plant. The narrative will clearly illustrate the direct evolution of the base camp elements to a minimal Mars architecture concept, and also outline unique development efforts that will be required in the next decade to make it possible to send humans to the Red Planet as early as the 2030s.

Greg Chavers↗
NASA NTRS1993

Engineering stategies and implications of using higher plants for throttling gas and water exchange in a controlled ecological life support system

Engineering stategies for advanced life support systems to be used on Lunar and Mars bases involve a wide spectrum of approaches. These range from purely physical-chemical life support strategies to purely biological approaches. Within the context of biological based systems, a bioengineered system can be devised that would utilize the metabolic mechanisms of plants to control the rates of CO2 uptake and O2 evolution (photosynthesis) and water production (transpiration). Such a mechanism of external engineering control has become known as throttling. Research conducted at the John F. Kennedy Space Center's Controlled Ecological Life Support System Breadboard Project has demonstrated the potential of throttling these fluxes by changing environmental parameters affecting the plant processes. Among the more effective environmental throttles are: light and CO2 concentration for controllingthe rate of photsynthesis and humidity and CO2 concentration for controlling transpiration. Such a bioengineered strategy implies control mechanisms that in the past have not been widely attributed to life support systems involving biological components and suggests a broad range of applications in advanced life support system design.

Chamberland, Dennis↗
NASA NTRS1998

A 5.8S nuclear ribosomal RNA gene sequence database: applications to ecology and evolution

We complied a 5.8S nuclear ribosomal gene sequence database for animals, plants, and fungi using both newly generated and GenBank sequences. We demonstrate the utility of this database as an internal check to determine whether the target organism and not a contaminant has been sequenced, as a diagnostic tool for ecologists and evolutionary biologists to determine the placement of asexual fungi within larger taxonomic groups, and as a tool to help identify fungi that form ectomycorrhizae.

Databases, Factual↗
NASA NTRS2013

Progress Towards an Interdisciplinary Science of Plant Phenology: Building Predictions Across Space, Time and Species Diversity

Climate change has brought renewed interest in the study of plant phenology - the timing of life history events. Data on shifting phenologies with warming have accumulated rapidly, yet research has been comparatively slow to explain the diversity of phenological responses observed across latitudes, growing seasons and species. Here, we outline recent efforts to synthesize perspectives on plant phenology across the fields of ecology, climate science and evolution. We highlight three major axes that vary among these disciplines: relative focus on abiotic versus biotic drivers of phenology, on plastic versus genetic drivers of intraspecific variation, and on cross-species versus autecological approaches. Recent interdisciplinary efforts, building on data covering diverse species and climate space, have found a greater role of temperature in controlling phenology at higher latitudes and for early-flowering species in temperate systems. These efforts have also made progress in understanding the tremendous diversity of responses across species by incorporating evolutionary relatedness, and linking phenological flexibility to invasions and plant performance. Future research with a focus on data collection in areas outside the temperate mid-latitudes and across species' ranges, alongside better integration of how risk and investment shape plant phenology, offers promise for further progress.

phenology↗
NASA NTRS1992

Lidar Investigation of Aerosol Pollution Distribution near a Coal Power Plant

Using aerosol lidars with high spatial and temporal resolution with the possibility of real-time data interpretation can solve a large number of ecological problems related to the aerosol-field distribution and variation and the structure of convective flows. Significantly less expensive specialized lidars are used in studying anthropogenic aerosols in the planetary boundary layer. Here, we present results of lidar measurements of the mass-concentration field around a coal-fired power plant with intensive local aerosol sources. We studied the pollution evolution as a function of the emission dynamics and the presence of retaining layers. The technique used incorporates complex analysis of three types of lidar mapping: horizontal map of the aerosol field, vertical cross-section map, and a series of profiles along a selected path. The lidar-sounding cycle was performed for the time of atmosphere's quasi-stationarity.

Mitsev, TS.↗
NASA NTRS1991

A Cretaceous-Tertiary mass extinction? Were most of Earth's species killed off?

For the past decade, the scientific and popular press have carried frequent articles about a catastrophic mass extinction that supposedly destroyed the majority of the earth's species, including the dinosaurs, approximately 65 million years ago. Since 1980, more than 2000 papers and books have dealt with some aspect of a mass extinction at the Cretaceous-Tertiary (K/T) boundary. One authoritative estimate of the severity of the extinctions is that 60-80% of all the living species became extinct at this boundary (Raup 1988). There appears to be a general acceptance of the fact that such a great catastrophe did occur. Most of the argument among scientists now is devoted to the determination of the cause. In this article, I argue that the species changes at the K/T boundary were neither sudden nor catastrophic. They were most likely caused by a regression of sea level that led to a decrease in primary production.

NASA Discipline Exobiology↗
NASA NTRS1993

Insect diversity in the fossil record

Insects possess a surprisingly extensive fossil record. Compilation of the geochronologic ranges of insect families demonstrates that their diversity exceeds that of preserved vertebrate tetrapods through 91 percent of their evolutionary history. The great diversity of insects was achieved not by high origination rates but rather by low extinction rates comparable to the low rates of slowly evolving marine invertebrate groups. The great radiation of modern insects began 245 million years ago and was not accelerated by the expansion of angiosperms during the Cretaceous period. The basic trophic machinery of insects was in place nearly 100 million years before angiosperms appeared in the fossil record.

NASA Discipline Exobiology↗
NASA NTRS1988

Patterns of megafloral change across the Cretaceous-Tertiary boundary in the Northern Great Plains and Rocky Mountains

The spatial and temporal distribution of vegetation in the terminal Cretaceous of Western Interior North America was a complex mosaic resulting from the interaction of factors including a shifting coastline, tectonic activity, a mild, possibly deteriorating climate, dinosaur herbivory, local facies effects, and a hypothesized bolide impact. In order to achieve sufficient resolution to analyze this vegetational pattern, over 100 megafloral collecting sites were established, yielding approximately 15,000 specimens, in Upper Cretaceous and lower Paleocene strata in the Williston, Powder River, and Bighorn basins in North Dakota, Montana, and Wyoming. These localities were integrated into a lithostratigraphic framework that is based on detailed local reference sections and constrained by vertebrate and palynomorph biostratigraphy, magnetostratigraphy, and sedimentary facies analysis. A regional biostratigraphy based on well located and identified plant megafossils that can be used to address patterns of floral evolution, ecology, and extinction is the goal of this research. Results of the analyses are discussed.

Johnson, Kirk R.↗
NASA NTRS1990

Documentation for Program SOILSIM: A computer program for the simulation of heat and moisture flow in soils and between soils, canopy and atmosphere

SOILSIM, a digital model of energy and moisture fluxes in the soil and above the soil surface, is presented. It simulates the time evolution of soil temperature and moisture, temperature of the soil surface and plant canopy the above surface, and the fluxes of sensible and latent heat into the atmosphere in response to surface weather conditions. The model is driven by simple weather observations including wind speed, air temperature, air humidity, and incident radiation. The model intended to be useful in conjunction with remotely sensed information of the land surface state, such as surface brightness temperature and soil moisture, for computing wide area evapotranspiration.

Field, Richard T.↗