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All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Electron acceleration in flares inferred from radio and hard X-ray emissions

Properties of electron acceleration in flares, especially the density structure in the acceleration region, are deduced from a correlation study between decimetric type III, spike, and hard X-ray (HXR) bursts. The high association rate found (71 percent) strongly suggests that spikes also originate from energetic electrons. Spikes and type III bursts have been found to be easily identified by their different polarizations. The two types of emission generally do not overlap in frequency. A reliable lower limit to the density is derived from the starting frequency of type III and U bursts. The spike emission very likely yields an upper limit. The density inhomogeneity in the acceleration region spans more than one order of magnitude and is more than one order of magnitude larger in the associated type U sources. A peak-to-peak correlation does not always exist between type III, spike and HXR bursts. This discrepancy can be interpreted in terms of the different source conditions and propagation properties. Whereas spikes need special conditions to become visible, type III and peaks of HXR may be the product of many elementary accelerations.

Benz, A. O.↗
NASA NTRS2009

Stability and Control Analysis of the F-15B Quiet SpikeTM Aircraft

The primary purpose of the Quiet Spike(TradeMark) flight research program was to analyze the aerodynamic, structural, and mechanical proof-of-concept of a large multi-stage telescoping nose spike installed on the National Aeronautics and Space Administration Dryden Flight Research Center (Edwards, California) F-15B airplane. This report describes the preflight stability and control analysis performed to assess the effect of the spike on the stability, controllability, and handling qualities of the airplane; and to develop an envelope expansion approach to maintain safety of flight. The overall flight test objective was to collect flight data to validate the spike structural dynamics and loads model up to Mach 1.8. Other objectives included validating the mechanical feasibility of a morphing fuselage at operational conditions and determining the near-field shock wave characterization. The two main issues relevant to the stability and control objectives were the effects of the spike-influenced aerodynamics on the F-15B airplane flight dynamics, and the air data and angle-of-attack sensors. The analysis covered the sensitivity of the stability margins, and the handling qualities due to aerodynamic variation and the maneuvering limitations of the F-15B Quiet Spike configuration. The results of the analysis and the implications for the flight test program are also presented.

McWherter, Shaun C.↗
NASA NTRS1990

Morphological Analyses of Spring Wheat (CIMMYT cv. PCYT-10) Somaclones

The objectives of this study were to induce callus from single immature wheat embryos, produce multiple seedlings from the induced callus, and analyse the somaclonal regenerants for potential grain production in a space garden. Immature wheat, Triticum aestivum L. (cv. PCYT-10), embryos were excised 10 to 12 days post-anthesis and cultured on modified Murashige and Skoog's inorganic salts. Embryos cultured on medium containing kinetin (6-furfurylaminopurine) at 0.5mg/l plus 2 or 3mg/l dicamba (1-methoxy-3,6- dichlorobenzoic acid) or 0.2mg/l 2,4-dichlorophenoxyacetic acid produced calli from which 24, 35 and 39% of the explant tissue exhibited regenerants, respectively. The size of flag leaves, plant heights, tillers per plant, spike lengths, awn lengths, and seeds per spike were significantly different in regenerants of two-selfed recurrent generations (SC(sub 1), SC(sub 2)) than in parental controls. However, there were no significant differences in spikelets per spike between the SC(sub 2) and parental controls. Desirable characteristics that were obtained included longer spikes, more seeds per spike, supernumerary spikelets, and larger flag leaves, variants that should be useful in wheat improvement programs.

Campbell, W. F.↗
NASA NTRS1999

Power Management in Regenerative Life Support Systems

Effective management of power can reduce the cost of launch and operation of regenerative life support systems. Variations in power may be quite severe and may manifest as surges or spikes, While the power plant may have some ability to deal with these variations, with batteries for example, over-capacity is expensive and does nothing to address the fundamental issue of excessive demand. Because the power unit must be sized to accommodate the largest demand, avoiding power spikes has the potential to reduce the required size of the power plant while at the same time increasing the dependability of the system. Scheduling of processors can help to reduce potential power spikes. However, not all power-consuming equipment is easily scheduled. Therefore, active power management is needed to further decrease the risk of surges or spikes. We investigate the use of a hierarchical scheme to actively manage power for a model of a regenerative life support system. Local level controllers individually determine subsystem power usage. A higher level controller monitors overall system power and detects surges or spikes. When a surge condition is detected, the higher level controller conducts an 'auction' and describes subsystem power usage to re-allocate power. The result is an overall reduction in total power during a power surge. The auction involves each subsystem making a 'bid' to buy or sell power based on local needs. However, this re-allocation cannot come at the expense of life support function. To this end, participation in the auction is restricted to those processes meeting certain tolerance constraints. These tolerances represent acceptable limits within which system processes can be operated. We present a simulation model and discuss some of our results.

Crawford, Sekou↗
NASA NTRS2000

Analysis of the Spaceflight Effects on Growth and Development of Super Dwarf Wheat Grown on the Space Station Mir

The hypothesis being tested is that Super Dwarf wheat, Triticum aestivum L., plants in the Svet Greenhouse onboard the Russian Space Station Mir will complete a life cycle in spaceflight, providing that the environmental conditions necessary for adequate growth on Earth are supplied. Twenty six seeds of wheat were planted in each of 2 rows of 2 root compartments for a total of 104 seeds in Svet. Germination rate at 7 d was 56 and 73% on Mir and 75 and 90% in ground-based controls. Plants were grown throughout the whole cycle of ontogenesis (123 d) with samples gathered at different times to validate the morphological and reproductive stages of the plants. Young plants showed vigorous early seedling growth, with large biomass production, including the formation of 280 floral spikes. Upon return to Earth, comparative analyses showed that the number of tillers and flowers per spikelet were 63.2% and 40% greater, respectively, in Mir-grown plants than in the controls. By contrast, the stem length (52.4%), spike mass (49.2%) and length (23.1%), awn length (75.7%), number of spikelets per spike (42.8%) and number of seeds per spike (100% sterile) from Mir-grown plants were substantially less than the controls. Distribution of moisture and roots throughout the substrate was very good. All florets on Mir-grown spikes ceased development at the same stage of ontogeny. Lack of caryopses formation was attributed to male sterility occurring at different stages of staminal development. Anthers failed to dehisce and pollen grains were smaller and shriveled compared to the controls, suggesting a chronic stress had occurred in the Svet growth chamber. Recent ground-based studies indicated that ethylene, which was measured at 0.3 to 1.8 mg per kilogram in the Mir, almost certainly could have induced male sterility in the wheat plants grown on the Mir.

Levinskikh, M. A.↗
NASA NTRS1992

Electrophysiology of the mammillary complex in vitro. II. Medial mammillary neurons

1. The electrophysiological properties of guinea pig medial mammillary body (MMB) neurons were studied using an in vitro slice preparation. 2. The neurons (n = 80) had an average resting potential of -57 +/- 5.5 (SD) mV, an input resistance of 176 +/- 83 M omega, and a spike amplitude of 58 +/- 15.7 mV. Most of the neurons were silent at rest (n = 52), but some fired spontaneous single spikes (n = 16) or spike bursts (n = 14). 3. The main electrophysiological characteristic of MMB neurons was the ability to generate Ca(2+)-dependent regenerative events, which resulted in very robust burst responses. However, this regenerative event was not the same for all neurons, ranging from typical low-threshold Ca2+ spikes (LTSs) to intermediate-threshold plateau potentials (ITPs). 4. The ITPs were distinct from the LTSs in that they lasted > or = 100 ms and were not inactivated at membrane potentials at or positive to -55 mV. 5. Some cells with a prominent ITP and no LTS (n = 36) displayed repetitive, usually rhythmic, bursting (n = 14). This ITP could be powerful enough to maintain rhythmic membrane potential oscillations after pharmacological block of Na+ conductances. 6. A group of 32 MMB neurons displayed complex bursting that was generated by activation of both LTSs and ITPs. This was established on the basis of their distinct time- and voltage-dependent characteristics. In a group of neurons (n = 14), the burst responses were exclusively generated by an LTS; however, a Ca(2+)-dependent plateau potential contributed to the generation of rebound-triggered oscillatory firing. 7. In addition to the Ca(2+)-dependent LTS and/or ITP, MMB neurons always displayed high-threshold Ca2+ spikes after reduction of K+ conductances with tetraethylammonium. 8. MMB neurons display one of the richer varieties of voltage-dependent Ca2+ conductances so far encountered in mammalian CNS. We propose that the very prominent endogenous bursting and oscillatory properties of MB neurons allow this nuclear complex to function as an oscillatory relay for the transmission of low-frequency rhythmic activities throughout the limbic circuit.

NASA Discipline Neuroscience↗
NASA NTRS1992

Electrophysiology of the mammillary complex in vitro. I. Tuberomammillary and lateral mammillary neurons

1. The electrophysiological properties of the tuberomammillary and lateral mammillary neurons in the guinea pig mammillary body were studied using an in vitro brain slice preparation. 2. Tuberomammillary (n = 79) neurons were recorded mainly ventral to the lateral mammillary body as well as ventromedially to the fornix within the rostral part of the medial mammillary nucleus. Intracellular staining with horseradish peroxidase (n = 9) and Lucifer yellow (n = 3) revealed that these cells have several thick, long, spiny dendrites emerging from large (20-35 microns) fusiform somata. 3. Most tuberomammillary neurons (66%) fired spontaneously at a relatively low frequency (0.5-10 Hz) at the resting membrane potential. The action potentials were broad (2.3 ms) with a prominent Ca(2+)-dependent shoulder on the falling phase. Deep (17.8 mV), long-lasting spike afterhyperpolarizations were largely Ca(2+)-independent. 4. All tuberomammillary neurons recorded displayed pronounced delayed firing when the cells were activated from a potential negative to the resting level. The cells also displayed a delayed return to the baseline at the break of hyperpolarizing pulses applied from a membrane potential level close to firing threshold. Analysis of the voltage- and time dependence of this delayed rectification suggested the presence of a transient outward current similar to the A current (IA). These were not completely blocked by high concentrations of 4-aminopyridine, whereas the delayed onset of firing was always abolished when voltage-dependent Ca2+ conductances were blocked by superfusion with Cd2+. 5. Tuberomammillary neurons also displayed inward rectification in the hyperpolarizing and, primarily, depolarizing range. Block of voltage-gated Na(+)-dependent conductances with tetrodotoxin (TTX) selectively abolished inward rectification in the depolarizing range, indicating the presence of a persistent low-threshold sodium-dependent conductance (gNap). In fact, persistent TTX-sensitive, plateau potentials were always elicited following Ca2+ block with Cd2+ when K+ currents were reduced by superfusion with tetraethylammonium. 6. The gNap in tuberomammillary neurons may subserve the pacemaker current underlying the spontaneous firing of these cells. The large-amplitude spike afterhyperpolarization of these neurons sets the availability of the transient outward rectifier, which, in conjunction with the pacemaker current, establishes the rate at which membrane potential approaches spike threshold. 7. Repetitive firing elicited by direct depolarization enhanced the spike shoulder of tuberomammillary neurons. Spike trains were followed by a Ca(2+)-dependent, apamine-sensitive, slow afterhyperpolarization. 8. Lateral mammillary neurons were morphologically and electrophysiologically different from tuberomammillary neurons. All lateral mammillary neurons neurons recorded (n = 44) were silent at rest (-60 mV).(ABSTRACT TRUNCATED AT 400 WORDS).

Non-NASA Center↗
NASA NTRS2005

Short Gamma-Ray Bursts with Extended Emission

The recent association of several short gamma-ray bursts (GRBs) with early type galaxies with low star formation rate demonstrates that short bursts arise from a different progenitor mechanism than long bursts. However, since the duration distributions of the two classes overlap, membership is not always easily established. The picture is complicated by the occasional presence of softer, extended emission lasting tens of seconds after the initial spike- like emission comprising an otherwise short burst. Using the large BATSE sample with time-tagged event (TTE) data, we show that the fundamental defining characteristic of the short burst class is that the initial spike exhibits negligible spectral evolution at energies above approx. 25 keV. This is behavior is nearly ubiquitous for the 260 bursts with T(sub 90) less than 2s where the BATSE TTE data type completely included the initial spike: Their spectral lags measured between the 25-50 keV and 100-300 energy ranges are consistent with zero in 90-95% of the cases, with most outliers probably representing the tail of the long burst class. We also analyze a small sample of "short" BATSE bursts - those with the most fluent, intense extended emission. The same lack of evolution on the pulse timescale obtains for the extended emission in the brighter bursts where significant measurements can be made. One possible inference is that both emission components may arise in the same region. We also show that the dynamic range in the ratio of peak intensities, spike : extended, is at least approx. l0(exp 3), and that for some bursts, the extended emission is only a factor of 2-5 lower. However, for our whole sample the total counts fluence of the extended component equals or exceeds that in the spike by a factor of several.

Norris, J. P.↗
NASA NTRS1958

Investigation of Inlet Control Parameters for an External-internal-compression Inlet from Mach 2.1 to 3.0

Investigation of the control parameters of an external-internal compression inlet indicates that the cowl-lip shock provides a signal to position the spike and to start the inlet over a Mach number range from 2.1 to 3.0. Use of a single fixed probe position to control the spike over the range of conditions resulted in a 3.7-count loss in total-pressure recovery at Mach 3.0 and 0 deg angle of attack. Three separate shock-sensing-probe positions were required to set the spike for peak recovery from Mach 2.1 to 3.0 and angles of attack from 0 deg to 6 deg. When the inlet was unstarted, an erroneous signal was obtained from the normal-shock control through most of the starting cycle that prevented the inlet from starting. Therefore, it was necessary to over-ride the normal-shock control signal and not allow the control to position the terminal shock until the spike was positioned.

POSITIONING EQUIPMENT↗
NASA NTRS1975

Occultation of beta Scorpii by Jupiter. V - The emersion of beta Scorpii C

Use of multicolor photometry to remove planetary limb contamination from occultation light curves is demonstrated. This color restoration procedure is shown to be more advantageous than limb scanning techniques since it allows continuous observation of the occultation. Sharp spikes appearing in the light curve of beta Sco C are compared with those observed during the occultation of beta Sco AB, and a model is developed for estimating the effects of all factors affecting the observed shape of a spike. The widths of the narrowest spikes are shown to correspond closely to the angular diameters of the occulted stars, suggesting that occultation spikes can be used to determine stellar diameters.

Elliot, J. L.↗
NASA NTRS1983

The water factor in harvest-sprouting of hard red spring wheat

Sprouting in unthreshed, ripe, hard red spring wheat (Triticum aestivum L.) is induced by rain, but sprouting does not necessarily occur because the crop is wetted. The spike and grain water conditions conducive to sprouting were determined in a series of laboratory experiments. Sprouting did not occur in field growing wheat wetted to 110% water concentration until the spike water concentration was reduced to 12% and maintained at this concentration for 2 days before wetting. When cut at growth stage 11.3, Feekes scale, Saratovskaya 20 (USSR) sprouted after 4 days drying, Olaf and Alex between 7 and 15 days drying and Columbus, recognized for its resistance to harvest time sprouting, after more than 15 days drying. Sprouting potential was enhanced after 4 wetting drying cycles in which any wetted interval was too brief to permit sufficient water imbibition to initiate sprouting. At harvest ripeness, grain water concentration exceeded spike water concentration by 0.7 percentage units. Following 6 months storage, 20% of the kernels in 300 spike bundles (simulating windrows) sprouted within 28 hrs after initiation of wetting to saturation (150% water concentration). Ninety percent sprouting occurred within 8 days in bundles maintained at 75% water concentration and higher, but less sprouting occurred in bundles dried to 50% water concentration before resaturation.

Bauer, A.↗
NASA NTRS1984

Methods to recover the narrow Dicke sub-Doppler feature in evacuated wall-coated cells without restrictions on cell size

The hyperfine resonance observed in evacuated wall-coated cells with dimensions lambda/2 (lambda is the hyperfine resonance wavelength) consists of a narrow Dicke sub-Doppler linewidth feature, the spike, superimposed on a broad pedestal. The hydrogen maser provides a classic example of this lineshape. As cell size is increased, an effect unique to evacuated wall-coated cells occurs. Certain combinations of microwave field distribution and cell size result in a lineshape having a pedestal with a small spike feature or only the broad pedestal with no spike. Such conditions are not appropriate for atomic frequency standard applications. The cause of the evacuated wall-coated cell lineshape is reviewed and methods to recover the narrow spike feature without restrictions on cell size is discussed. One example is a cell with dimensions having equal volumes of exposure to opposite phases of the microwave magnetic field.

Robinson, H. G.↗
NASA NTRS1986

Relation between solar narrow-band decimeter wave bursts and associated X-ray bursts

Results are reported of an initial comparison of solar narrow-band decimeter wave spike bursts with corresponding X-ray events for 25 solar flares. Contrary to the rather straighforward temporal and spatial relations which exist between typical impulsive microwave and X-ray bursts, narrow-band decimeter wave spike bursts show complex temporal structure relative to the associated X-ray features. The time delay between the hard X-ray and microwave emission peaks varies from -2 to 8 seconds. The associated X-ray events are very weak in intensity, are spectrally very soft, and do not show any peculiar spectral features. Although the total number of bursts is small, it is found that decimeter spike bursts are 100 to 1000 times stronger than normal impulsive microwave bursts for the same observed amount of hard X-ray emission. This feature, supplemented by the fact that 100% circular polarization is observed, strongly supports a maser origin for the decimeter spike bursts.

Enome, Shinzo↗
NASA NTRS1991

An analytical comparison of convective heat transfer correlations in supercritical hydrogen

Four correlations that cover the ranges of liquid to gas for turbulent flow convection of hydrogen are compared with CFD analysis over a range of expected design conditions for active cooling of hypersonic aircraft. Analysis of hydrogen cooling in a typical cooling panel shows how predicted design performance varies with the correlation utilized. The CFD heat transfer coefficient results for a heat spike differed significantly from all four correlations. An acceptable heat transfer coefficient can be calculated at the heat spike location by overlooking the coefficient at the spike and averaging the coefficient before and after the spike.

Dziedzic, William M.↗
NASA NTRS1998

A New and Fast Method for Smoothing Spectral Imaging Data

The Airborne Visible Infrared Imaging Spectrometer (AVIRIS) acquires spectral imaging data covering the 0.4 - 2.5 micron wavelength range in 224 10-nm-wide channels from a NASA ER-2 aircraft at 20 km. More than half of the spectral region is affected by atmospheric gaseous absorption. Over the past decade, several techniques have been used to remove atmospheric effects from AVIRIS data for the derivation of surface reflectance spectra. An operational atmosphere removal algorithm (ATREM), which is based on theoretical modeling of atmospheric absorption and scattering effects, has been developed and updated for deriving surface reflectance spectra from AVIRIS data. Due to small errors in assumed wavelengths and errors in line parameters compiled on the HITRAN database, small spikes (particularly near the centers of the 0.94- and 1.14-micron water vapor bands) are present in this spectrum. Similar small spikes are systematically present in entire ATREM output cubes. These spikes have distracted geologists who are interested in studying surface mineral features. A method based on the "global" fitting of spectra with low order polynomials or other functions for removing these weak spikes has recently been developed by Boardman (this volume). In this paper, we describe another technique, which fits spectra "locally" based on cubic spline smoothing, for quick post processing of ATREM apparent reflectance spectra derived from AVIRIS data. Results from our analysis of AVIRIS data acquired over Cuprite mining district in Nevada in June of 1995 are given. Comparisons between our smoothed spectra and those derived with the empirical line method are presented.

Gao, Bo-Cai↗
NASA NTRS2004

Winds, Water Budgets and Stable Isotopes in Tropical Cyclones using TRMM and QUICKSCAT

Water vapor is the most abundant greenhouse gas in the atmosphere. Changes in its concentration and distribution are controlled by the hydrologic cycle. Because of its capacity to absorb and emit long wave radiation, release latent heat during condensation in storms and reflect short wave radiation when clouds form it has a major impact on Global climate change. The stable isotope ratios of water are H20 H2l6O and H0 H2l6O. These ratios change whenever water undergoes a phase change. They also change in both rain and water vapor whenever an air parcel is exposed to rain. In addition the relative changes in the two ratios differ as a &nction of the relative humidity. In short, the stable isotope ratios in water vapor in the atmosphere contain an integrated history of the processes affecting the concentration and distribution of water vapor in the atmosphere. Therefore the measurement and interpretation of changes in these stable isotope ratios are a powerful tool matched by no other method in tracing the transport history of water in the atmosphere. Our initial studies under this grant focused on the changes of the stable isotope ratios of precipitation and water vapor in tropical cyclones. The changes in time and space were found to be very large and to trace the transport of water in the storms reflecting changes in basic structural features. Because the stable isotope ratios of rains from tropical cyclones are so low flooding associated with land falling tropical cyclones introduces a negative isotopic spike into the coastal surface waters. In addition the stable isotope ratios of water vapor in the vicinity of tropical cyclones is anomalously low. This suggests that carbonate shelled organisms such as ostracoda living in coastal waters have the potential to record the isotopic spike and thereby provide a long term record of tropical storm activity in sediment cores containing fossil shells. Likewise, tree rings in coastal environments offer a similar potential. We have analyzed the oxygen isotopic composition of ostrcoda shells formed in the floodwaters of Tropical Storm Allison (2001) and discovered the negative isotopic 1 16 spike. Because we had learned that storm activity has a major impact on the stable isotope ratios of water vapor in the tropics and sub-tropics we decided to analyze the isotopic compositions of water vapor in different locations in the tropics. We did this in Puerto Escondido, Mexico in July 1998, near Kwajalein Island in the Pacific in 1999 as part of a TRMM summer field program and in 2001 in Key West, Florida as part of the CAMEX 4 summer field program. Our isotopic studies along with our earlier tropical cyclone studies showed that the low isotopic ratios in water vapor induced by exposure to rains the storms persisted for 48 hours often far away from the original storm site. We also noted that positive isotopic spikes were introduced into atmospheric water vapor if winds were high and extensive sea spray was present. These findings have a significant impact on the interpretation of the stable isotope studies of tropical ice cores found in the high mountain regions of the tropics. The assumption made in interpreting the ice core record is that the source water vapor evaporated from the sea surface is in near isotopic equilibrium with the seawater and undergoes a decrease during its transport that reflects the change in temperature from the sea surface to the site of the ice core. Because an additional isotopic depletion occurs at the sea surface source area that depends on the intensity, duration and size of the tropical rain system the isotopic variations found in the ice cores must take into account changes in past storm activity in the tropics. These systems must be an important source of water vapor to the ice cores because they charge the troposphere with water vapor to a far greater vertical height than evaporation in quiescent regions. Finally, an interest in increased heat transfer in thnterior of tropical cyclones resulting from greater amounts of sea spray is a topic of considerable interest to the research community. Increases in sea spray may be related to rapid changes in the intensity of hurricanes, a feature of hurricanes that currently is very poorly forecast. Project CBLAST of the Hurricane Research Division of NOAA is an active program that uses P3 research aircraft to evaluate this problem. An instrument has been designed and built at the University of Houston that will be placed on the P3 research aircraft during the 2004 hurricane season. It continuously measures the salt content of rain in hurricanes. Changes in the salt content of the rains should reflect the abundance of sea spray at the sea surface. In this way maps of sea spray intensity in hurricanes may be forthcoming. This should help computer modelers who simulate hurricanes to better understand the potential of changes in sea spray to change the intensity of hurricanes. The cost of designing, building and installing this instrument was borne largely by funding from this NASA grant. A list of presentations at national meetings and publications that were as the result of funding from this NASA grant are found in the report.

Lawrence, James R.↗
NASA NTRS2001

State-space receptive fields of semicircular canal afferent neurons in the bullfrog

Receptive fields are commonly used to describe spatial characteristics of sensory neuron responses. They can be extended to characterize temporal or dynamical aspects by mapping neural responses in dynamical state spaces. The state-space receptive field of a neuron is the probability distribution of the dynamical state of the stimulus-generating system conditioned upon the occurrence of a spike. We have computed state-space receptive fields for semicircular canal afferent neurons in the bullfrog (Rana catesbeiana). We recorded spike times during broad-band Gaussian noise rotational velocity stimuli, computed the frequency distribution of head states at spike times, and normalized these to obtain conditional pdfs for the state. These state-space receptive fields quantify what the brain can deduce about the dynamical state of the head when a single spike arrives from the periphery. c2001 Elsevier Science B.V. All rights reserved.

Non-NASA Center↗
NASA NTRS1997

Reproductive Ontogeny of Wheat Grown on the MIR Space Station

The reproductive ontogeny of 'Super-Dwarf' wheat grown on the space station Mir is chronicled from the vegetative phase through flower development. Changes in the apical meristem associated with transition From the vegetative phase to floral initiation and development of the reproductive spike were all typical of 'Super Dwarf' wheat up to the point of anthesis. Filament elongation, which characteristically occurs just prior to anthesis and moves the anthers through the stigmatic branches thus facilitating pollination, did no1 xcur in the flowers of spikes grown on Mir. While development of spikes on tillers typically occurs later :han that of spikes on the main stem, all flowers appear to be arrested at the same developmental point.

Bubenheim, David L.↗