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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Differences in the response of wheat, soybean and lettuce to reduced blue radiation

Although many fundamental blue light responses have been identified, blue light dose-response curves are not well characterized. We studied the growth and development of soybean, wheat and lettuce plants under high-pressure sodium (HPS) and metal halide (MH) lamps with yellow filters creating five fractions of blue light. The blue light fractions obtained were < 0.1, 2 and 6% under HPS lamps, and 6, 12 and 26% under MH lamps. Studies utilizing both lamp types were done at two photosynthetic photon flux levels, 200 and 500 mumol m-2 s-1 under a 16 h photoperiod. Phytochrome photoequilibria was nearly identical among treatments. The blue light effect on dry mass, stem length, leaf area, specific leaf area and tillering/branching was species dependent. For these parameters, wheat did not respond to blue light, but lettuce was highly sensitive to blue light fraction between 0 and 6% blue. Soybean stem length decreased and leaf area increased up to 6% blue, but total dry mass was unchanged. The blue light fraction determined the stem elongation response in soybean, whereas the absolute amount of blue light determined the stem elongation response in lettuce. The data indicate that lettuce growth and development requires blue light, but soybean and wheat may not.

NASA Discipline Life Support Systems↗
NASA NTRS1999

Double Diffusive Convection in Materials Processing

A great number of crystals grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity (g-jitter). As a specific example, past HgCdTe crystal growth space experiments by Lehoczky and co-workers indicate radial compositional asymmetry in the grown crystals. In the case of HgCdTe the rejected component into the melt upon solidification is HgTe which is denser than the melt. The space grown crystals indicate the presence of three dimensional flow with the heavier HgTe-rich material clearly aligned with the residual gravity (0.55-1.55 micro g) vector. This flow stems from double-diffusive convection, namely, thermal and solutal buoyancy driven flow in the melt. The study of double-diffusive convection is multi-faceted and rather vast. In our investigation, we seek to focus on one specific aspect of this discipline that is of direct relevance to materials processing especially crystal growth, namely, the side ways heating regime. This problem has been widely studied, both experimentally and numerically, in the context of solar ponds wherein the system is characterized by a linear salt (solutal) gradient with an imposed lateral temperature gradient. The induced flow instabilities arise from the wide disparity between the fluid thermal diffusivity and the solute diffusivity. The extension of the analysis to practical crystal growth applications has however not been rigorously made and understood. One subtle but important difference in crystal growth systems is the fact that die system solute gradient is non-linear (typically exponential). Besides, the crystal growth problem has the added complexities of solidification, both lateral and longitudinal thermal gradients and segregation phenomena in systems where binary and ternary compounds are being grown. This paper treats the side ways heating problem alone in a model fluid system. Results from detailed numerical calculations, mainly two dimensional are provided. The interactions between a non-linear solute gradient and an imposed transverse thermal gradient are investigated. The buoyancy effects are treated in the traditional Boussinesq approximation and also in a more complete density formulation to address recent concerns of the first approach especially in simulations of the system response in a reduced gravity environment. Detailed flow, temperature and solute field plots along with heat and mass transfer results are presented in the paper. Implications to practical crystal growth systems as discerned from the modeling results are also explored and reported.

Ramachandra, Narayanan↗
NASA NTRS1997

Anatomical features of pepper plants (Capsicum annuum L.) grown under red light-emitting diodes supplemented with blue or far-red light

Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves and stems. One LED (660) array supplied 90% red light at 660 nm (25nm band-width at half-peak height) and 1% far-red light between 700-800nm. A second LED (660/735) array supplied 83% red light at 660nm and 17% far-red light at 735nm (25nm band-width at half-peak height). A third LED (660/blue) array supplied 98% red light at 660nm, 1% blue light between 350-550nm, and 1% far-red light between 700-800nm. Control plants were grown under broad spectrum metal halide lamps. Plants were gron at a mean photon flux (300-800nm) of 330 micromol m-2 s-1 under a 12 h day-night photoperiod. Significant anatomical changes in stem and leaf morphologies were observed in plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of choloplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660/blue LED array, and lowest in peppers grown under the 660 or 660/735 LED arrays. Most anatomical features of pepper stems and leaves were similar among plants grown under 660 or 660/735 LED arrays. The effects of spectral quality on anatomical changes in stem and leaf tissues of peppers generally correlate to the amount of blue light present in the primary light source.

NASA Discipline Life Support Systems↗
NASA NTRS1991

The pH profile for acid-induced elongation of coleoptile and epicotyl sections is consistent with the acid-growth theory

The acid-growth theory predicts that a solution with a pH identical to that of the apoplast of auxin-treated tissues (4.5.-5.0) should induce elongation at a rate comparable to that of auxin. Different pH profiles for elongation have been obtained, however, depending on the type of pretreatment between harvest of the sections and the start of the pH-incubations. To determine the acid sensitivity under in vivo conditions, oat (Avena sativa L.) coleoptile, maize (Zea mays L.) coleoptile and pea (Pisum sativum L.) epicotyl sections were abraded so that exogenous buffers could penetrate the free space, and placed in buffered solutions of pH 3.5-6.5 without any preincubation. The extension, without auxin, was measured over the first 3 h. Experiments conducted in three laboratories produced similar results. For all three species, sections placed in buffer without pretreatment elongated at least threefold faster at pH 5.0 than at 6.0 or 6.5, and the rate elongation at pH 5.0 was comparable to that induced by auxin. Pretreatment of abraded sections with pH-6.5 buffer or distilled water adjusted to pH 6.5 or above gave similar results. We conclude that the pH present in the apoplast of auxin-treated coleoptile and stems is sufficiently low to account for the initial growth response to auxin.

NASA Discipline Plant Biology↗
NASA NTRS1986

Kinetics of shoot inversion-induced ethylene production in Pharbitis nil

Shoot inversion promotes a significant increase in ethylene production in the inverted part of the Pharbitis nil main shoot. The latent period for shoot inversion-induced ethylene production is ca. 2.75 h. Our results indicate that the shoot-inversion ethylene response is not persistent and can be terminated and rapidly reinitiated by appropriate alteration of the orientation of the main shoot regardless of prolonged previous exposures of the shoot to various orientations. The time course of the production of ACC (1-aminocyclopropane-1-carboxylic acid), the immediate precursor of ethylene, follows a pattern similar to that of ethylene during the various alterations of shoot orientation. Excised stem segments and intact stems are capable of induction, inhibition, and reinduction of ethylene evolution. Ethylene production reported here for shoot inversion does not result from segmenting (wounding) of the tissue.

NASA Discipline Number 40-10↗
NASA NTRS2000

atonal regulates neurite arborization but does not act as a proneural gene in the Drosophila brain

Drosophila atonal (ato) is the proneural gene of the chordotonal organs (CHOs) in the peripheral nervous system (PNS) and the larval and adult photoreceptor organs. Here, we show that ato is expressed at multiple stages during the development of a lineage of central brain neurons that innervate the optic lobes and are required for eclosion. A novel fate mapping approach shows that ato is expressed in the embryonic precursors of these neurons and that its expression is reactivated in third instar larvae (L3). In contrast to its function in the PNS, ato does not act as a proneural gene in the embryonic brain. Instead, ato performs a novel function, regulating arborization during larval and pupal development by interacting with Notch.

NASA Discipline Developmental Biology↗
NASA NTRS2002

Precambrian animal life: probable developmental and adult cnidarian forms from Southwest China

The evolutionary divergence of cnidarian and bilaterian lineages from their remote metazoan ancestor occurred at an unknown depth in time before the Cambrian, since crown group representatives of each are found in Lower Cambrian fossil assemblages. We report here a variety of putative embryonic, larval, and adult microfossils deriving from Precambrian phosphorite deposits of Southwest China, which may predate the Cambrian radiation by 25-45 million years. These are most probably of cnidarian affinity. Large numbers of fossilized early planula-like larvae were observed under the microscope in sections. Though several forms are represented, the majority display remarkable conformity, which is inconsistent with the alternative that they are artifactual mineral inclusions. Some of these fossils are preserved in such high resolution that individual cells can be discerned. We confirm in detail an earlier report of the presence in the same deposits of tabulates, an extinct crown group anthozoan form. Other sections reveal structures that most closely resemble sections of basal modern corals. A large number of fossils similar to modern hydrozoan gastrulae were also observed. These again displayed great morphological consistency. Though only a single example is available, a microscopic animal remarkably similar to a modern adult hydrozoan is also presented. Taken together, the new observations reported in this paper indicate the existence of a diverse and already differentiated cnidarian fauna, long before the Cambrian evolutionary event. It follows that at least stem group bilaterians must also have been present at this time.

Non-NASA Center↗
NASA NTRS1997

Cellular mechanisms underlying growth asymmetry during stem gravitropism

Plant stems respond to gravitropic stimulation with a rapid, local and reversible change in cell growth rate (elongation), generally on both the upper and lower sides of the stem. The cellular and biochemical mechanisms for this differential growth are reviewed. Considerable evidence implicates an asymmetry in wall pH in the growth response. The strengths and weaknesses of the wall "loosening enzyme" concept are reviewed and the possibility of expansin involvement in the bending response of stems is considered. Also discussed is the possibility that wall stiffening processes, e.g. phenolic coupling driven by oxidative bursts or altered orientation of newly deposited cellulose, might mediate the growth responses during gravitropism.

NASA Discipline Plant Biology↗
NASA NTRS1992

Cellular distribution of calmodulin and calmodulin-binding proteins in Vicia faba L

The distribution of calmodulin (CaM) and CaM-binding proteins within Vicia faba was investigated. Both CaM and CaM-binding proteins were found to be differentially distributed among organs, tissues, and protoplast types. CaM levels, on a per protein basis, were found to be the highest in leaf epidermis, containing 3-fold higher levels of CaM than in total leaf. Similarly, guard cell and epidermal cell protoplasts were also found to have higher levels of CaM than mesophyll cell protoplasts. 125I-CaM blot overlay assays were performed to qualitatively examine CaM-binding proteins in these protoplast types as well as in whole tissues and organs. CaM-binding proteins with Mr 52,000, 78,000, and 115,000 were common in all metabolically active plant parts. Unique CaM-binding protein bands were detected in guard cell protoplasts (Mr 39,000, 88,000), stems (Mr 45,000, 60,000, 64,000), and roots (Mr 62,000), suggesting the presence of specialized CaM-dependent processes in these cells and organs.

Non-NASA Center↗
NASA NTRS1986

The control of apical dominance: localization of the growth region of the Pharbitis nil shoot

The growing region of the upright Pharbitis nil shoot extends over a distance 13 cm basipetal to the shoot apex. When the shoot is inverted, ethylene production in this region is greatly enhanced whereas stem elongation is significantly inhibited. This growth region is ethylene-sensitive and the restriction of its growth by shoot inversion-induced ethylene may mediate the release of apical dominance.

NASA Discipline Plant Biology↗
NASA NTRS1988

Effects of mechanical stress or abscisic acid on growth, water status and leaf abscisic acid content of eggplant seedlings

Container-grown eggplant (Solanum melongena L. var esculentum Nees. 'Burpee's Black Beauty') seedlings were conditioned with brief, periodic mechanical stress or abscisic acid (ABA) in a greenhouse prior to outdoor exposure. Mechanical stress consisted of seismic (shaking) or thigmic (stem flexing) treatment. Exogenous ABA (10(-3) or 10(-4)M) was applied as a soil drench 3 days prior to outdoor transfer. During conditioning, only thigmic stress reduced stem elongation and only 10(-3) M ABA reduced relative growth rate (RGR). Both conditioning treatments increased leaf specific chlorophyll content, but mechanical stress did not affect leaf ABA content. Outdoor exposure of unconditioned eggplant seedlings decreased RGR and leaf-specific chlorophyll content, but tended to increase leaf ABA content relative to that of plants maintained in the greenhouse. Conditioning did not affect RGR of plants subsequently transferred outdoors, but did reduce stem growth. Seismic stress applied in the greenhouse reduced dry weight gain by plants subsequently transferred outdoors. Mechanical stress treatments increased leaf water potential by 18-25% relative to that of untreated plants.

NASA Discipline Plant Biology↗
NASA NTRS1998

Light promotion of hypocotyl gravitropism of a starch-deficient tobacco mutant correlates with plastid enlargement and sedimentation

Dark-grown hypocotyls of a starch-deficient mutant (NS458) of tobacco (Nicotiana sylvestris) lack amyloplasts and plastid sedimentation, and have severely reduced gravitropism. However, gravitropism improved dramatically when NS458 seedlings were grown in the light. To determine the extent of this improvement and whether mutant hypocotyls contain sedimented amyloplasts, gravitropic sensitivity (induction time and intermittent stimulation) and plastid size and position in the endodermis were measured in seedlings grown for 8 d in the light. Light-grown NS458 hypocotyls were gravitropic but were less sensitive than the wild type (WT). Starch occupied 10% of the volume of NS458 plastids grown in both the light and the dark, whereas WT plastids were essentially filled with starch in both treatments. Light increased plastid size twice as much in the mutant as in the WT. Plastids in light-grown NS458 were sedimented, presumably because of their larger size and greater total starch content. The induction by light of plastid sedimentation in NS458 provides new evidence for the role of plastid mass and sedimentation in stem gravitropic sensing. Because the mutant is not as sensitive as the WT, NS458 plastids may not have sufficient mass to provide full gravitropic sensitivity.

Non-NASA Center↗
NASA NTRS2002

The western red cedar (Thuja plicata) 8-8' DIRIGENT family displays diverse expression patterns and conserved monolignol coupling specificity

The isolation and characterization of a multigene family of the first class of dirigent proteins (namely that mainly involved in 8-8' coupling leading to (+)-pinoresinol in this case) is reported, this comprising of nine western red cedar (Thuja plicata) DIRIGENT genes (DIR1-9) of 72-99.5% identity to each other. Their corresponding cDNA clones had coding regions for 180-183 amino acids with each having a predicted molecular mass of ca. 20 kDa including the signal peptide. Real time-PCR established that the DIRIGENT isovariants were differentially expressed during growth and development of T. plicata (P < 0.05). The phylogenetic relationships and the rates and patterns of nucleotide substitution suggest that the DIRIGENT gene may have evolved via paralogous expansion at an early stage of vascular plant diversification. Thereafter, western red cedar paralogues have maintained an high homogeneity presumably via a concerted evolutionary mode. This, in turn, is assumed to be the driving force for the differential formation of 8-8'-linked pinoresinol derived (poly)lignans in the needles, stems, bark and branches, as well as for massive accumulation of 8-8'-linked plicatic acid-derived (poly)lignans in heartwood.

Non-NASA Center↗
NASA NTRS1987

Hematological measurements in rats flown on Spacelab shuttle, SL-3

Previous studies have shown that a decrease in red cell mass occurs in astronauts, and some studies indicate a leukocytosis occurs. A life science module housing young and mature rats was flown on shuttle mission Spacelab 3 (SL-3), and the results of hematology studies of flight and control rats are presented. Statistically significant increases in the hematocrit, red blood cell counts, and hemoglobin determinations, together with a mild neutrophilia and lymphopenia, were found in flight animals. No significant changes were found in bone marrow and spleen cell differentials or erythropoietin determinations. Clonal assays demonstrated an increased erythroid colony formation of flight animal bone marrow cells at erythropoietin doses of 0.02 and 1.0 U/ml but not 0.20 U/ml. These results agree with some but vary from other previously published studies. Erythropoietin assays and clonal studies were performed for the first time.

NASA Experiment Number SL3-26↗
NASA NTRS1999

Gravitropism of inflorescence stems in starch-deficient mutants of Arabidopsis

Previous studies have assayed the gravitropic response of roots and hypocotyls of wild type Arabidopsis thaliana, two reduced-starch strains, and a starchless strain. Because there have been few reports on inflorescence gravitropism, in this article, we use microscopic analyses and time-course studies of these mutants and their wild type to study gravitropism in these stems. Sedimentation of plastids was observed in endodermal cells of the wild type and reduced-starch mutants but not in the starchless mutant. In all of these strains, the short inflorescence stems (1.0-2.9 cm) were less responsive to the gravistimulus compared with the long stems (3.0-6.0 cm). In both long and short inflorescence stems, the wild type initially had the greatest response; the starchless mutant had the least response; and the reduced starch mutants exhibited an intermediate response. Furthermore, growth rates among all four strains were approximately equal. At about 6 h after reorientation, inflorescences of all strains returned to a position parallel to the gravity vector. Thus, in inflorescence stems, sedimentation of plastids may act as an accelerator but is not required to elicit a gravitropic response. Furthermore, the site of perception appears to be diffuse throughout the inflorescence stem. These results are consistent with both a plastid-based statolith model and the protoplast pressure hypothesis, and it is possible that multiple systems for gravity perception occur in plant cells.

Non-NASA Center↗
NASA NTRS1987

Wall relaxation and the driving forces for cell expansive growth

When water uptake by growing cells is prevented, the turgor pressure and the tensile stress in the cell wall are reduced by continued wall loosening. This process, termed in vivo stress relaxation, provides a new way to study the dynamics of wall loosening and to measure the wall yield threshold and the physiological wall extensibility. Stress relaxation experiments indicate that wall stress supplies the mechanical driving force for wall yielding. Cell expansion also requires water absorption. The driving force for water uptake during growth is created by wall relaxation, which lowers the water potential of the expanding cells. New techniques for measuring this driving force show that it is smaller than believed previously; in elongating stems it is only 0.3 to 0.5 bar. This means that the hydraulic resistance of the water transport pathway is small and that rate of cell expansion is controlled primarily by wall loosening and yielding.

NASA Program Space Biology↗
NASA NTRS1991

The epidermis of the pea epicotyl is not a unique target tissue for auxin-induced growth

Previous research has suggested that the epidermis of dicotyledonous stems is the primary site of auxin action in elongation growth. We show for pea (Pisum sativum L.) epicotyl sections that this hypothesis is incorrect. In buffer (pH 6.5), sections from which the outer cell layers were removed (peeled) elongated slowly and to the same extent as intact sections. Addition of 10 micromolar indoleacetic acid to this incubation medium caused peeled sections to grow to the same extent and with the same kinetics as auxin-treated nonpeeled sections. This indicates that both epidermis and cortical tissues have the ability to respond rapidly to auxin and that the epidermis is not the sole site of auxin action in dicotyledonous stems. Previous reports that peeled pea sections respond poorly to auxin may have resulted from an acid extension of these sections due to the use of distilled water as the incubation medium.

Non-NASA Center↗