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1.
The electric sense of elasmobranch fishes (sharks and rays) is an important sensory modality known to mediate the detection of bioelectric stimuli. Although the best known function for the use of the elasmobranch electric sense is prey detection, relatively few studies have investigated other possible biological functions. Here, we review recent studies that demonstrate the elasmobranch electrosensory system functions in a wide number of behavioral contexts including social, reproductive and anti-predator behaviors. Recent work on non-electrogenic stingrays demonstrates that the electric sense is used during reproduction and courtship for conspecific detection and localization. Electrogenic skates may use their electrosensory encoding capabilities and electric organ discharges for communication during social and reproductive interactions. The electric sense may also be used to detect and avoid predators during early life history stages in many elasmobranch species. Embryonic clearnose skates demonstrate a ventilatory freeze response when a weak low-frequency electric field is imposed upon the egg capsule. Peak frequency sensitivity of the peripheral electrosensory system in embryonic skates matches the low frequencies of phasic electric stimuli produced by natural fish egg-predators. Neurophysiology experiments reveal that electrosensory tuning changes across the life history of a species and also seasonally due to steroid hormone changes during the reproductive season. We argue that the ontogenetic and seasonal variation in electrosensory tuning represent an adaptive electrosensory plasticity that may be common to many elasmobranchs to enhance an individual's fitness throughout its life history. 相似文献
2.
T. C. Tricas J. G. New 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):89-101
Elasmobranch fishes localize weak electric sources at field intensities of <5 ηV cm−1, but the response dynamics of electrosensory primary afferent neurons to near threshold stimuli in situ are not well characterized.
Electrosensory primary afferents in the round stingray, Urolophus halleri, have a relatively high discharge rate, a regular discharge pattern and entrain to 1-Hz sinusoidal peak electric field gradients
of ≤20 ηV cm−1. Peak neural discharge for units increases as a non-linear function of stimulus intensity, and unit sensitivity (gain) decreases
as stimulus intensity increases. Average peak rate-intensity encoding is commonly lost when peak spike rate approximately
doubles that of resting, and for many units occurs at intensities <1 μV cm−1. Best neural sensitivity for nearly all units is at 1–2 Hz with a low-frequency slope of 8 dB/decade and a high-frequency
slope of −23 dB/decade. The response characteristics of stingray electrosensory primary afferents indicate sensory adaptations
for detection of extremely weak phasic fields near 1–2 Hz. We argue that these properties reflect evolutionary adaptations
in elasmobranch fishes to enhance detection of prey, communication and social interactions, and possibly electric-mediated
geomagnetic orientation.
Accepted: 20 June 1997 相似文献
3.
M. E. Nelson Z. Xu J. R. Payne 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,181(5):532-544
The first stage of information processing in the electrosensory system involves the encoding of local changes in transdermal
potential into trains of action potentials in primary electrosensory afferent nerve fibers. To develop a quantitative model
of this encoding process for P-type (probability-coding) afferent fibers in the weakly electric fish Apteronotus leptorhynchus, we recorded single unit activity from electrosensory afferent axons in the posterior branch of the anterior lateral line
nerve and analyzed responses to electronically generated sinusoidal amplitude modulations of the local transdermal potential.
Over a range of AM frequencies from 0.1 to 200 Hz, the modulation transfer function of P-type afferents is high-pass in character,
with a gain that increases monotonically up to AM frequencies of 100 Hz where it begins to roll off, and a phase advance with
a range of 15–60 degrees. Based on quantitative analysis of the observed gain and phase characteristics, we present a computationally
efficient model of P-type afferent response dynamics which accurately characterizes changes in afferent firing rate in response
to amplitude modulations of the fish's own electric organ discharge over a wide range of AM frequencies relevant to active
electrolocation.
Accepted: 14 June 1997 相似文献
4.
Investigations using electrical impedance spectroscopy to measure the responses of fish embryos to the cryoprotective chemicals,
methanol and dimethyl sulphoxide (DMSO), were carried out. Zebrafish (Danio rerio) embryos were used as a model to study the newly proposed technique. The normalised permittivity and conductivity changes
of the embryos were measured continuously over a 20-min period in a customised embryo-holding chamber. The normalised permittivity
and conductivity spectra were obtained during embryo exposure to different concentrations of methanol (1.0, 2.0 and 3.0 M)
and DMSO (0.5, 1.0 and 2.0 M) solutions. The results showed significant permittivity and conductivity changes after embryo
exposure to methanol and DMSO at the optimum embryo loading level (six embryos). Embryos in different concentrations of methanol
and DMSO also resulted in quantitative responses shown in the normalised permittivity and conductivity spectra. The results
demonstrated that fish embryo membrane permeability to cryoprotective chemicals could be monitored in real-time. The measurement
of permittivity at a lower frequency range (10–103 Hz) and conductivity at a higher frequency range (104–106 Hz) during fish embryo exposure to cryoprotective chemicals using impedance spectroscopy can be used as a new tool for the
fast screening of most effective cryoprotective chemicals. The results from the present study also demonstrated the possibility
of quantifying the level of cryoprotective chemicals penetrating the fish embryos. 相似文献
5.
I. Kaunzinger B. Kramer 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,179(3):323-330
The electric organ discharge (EOD) of the South American knifefish Eigenmannia sp. is a permanently present wave signal of usually constant amplitude and frequency (similar to a sine wave). A fish perceives discharges of other fish as a modulation of its own. At frequency identity (F = 0 Hz) the phase difference between a fish's own electric discharge and that of another fish affects the superimposed waveform. It was unclear whether or not the electrosensory stimulus-intensity threshold as behaviourally determined depends on the phase difference between a fish's own EOD and a sine-wave stimulus (at F = 0 Hz). Also the strength of the jamming avoidance response (JAR), a discharge frequency shift away from a stimulus that is sufficiently close to the EOD frequency, as a function of phase difference was studied. Sine-wave stimuli were both frequency-clamped and phase-locked to a fish's discharge frequency (F = 0 Hz). In food-rewarded fish, the electrosensory stimulus-intensity threshold depended significantly on the phase difference between a fish's discharge and the stimulus. Stimulus-intensity thresholds were low (down to 3 V/cm, peak-to-peak) when the superimposed complex wave changed such that the shift in zero-crossings times relative to the original EOD was large but amplitude change minimal; stimulus-intensity thresholds were high (up to 16.9 V/cm, peak-to-peak) when the shift in zero-crossings times was small but amplitude change maximal. Similar results were obtained for the non-conditioned JAR: at constant supra-threshold stimulus intensities and F = 0 Hz, the phase difference significantly affected the strength of the JAR, although variability between individuals was higher than that observed in the conditioned experiments.Abbreviations
ACP
active phase coupling
-
EOD
electric organ discharge
-
JAR
jamming avoidance response
-
F
frequency (fish) — frequency (stimulus) [Hz]
-
p-p
peak-to-peak 相似文献
6.
During the day, weakly electric snoutfish, such as Marcusenius altisambesi from the Okavango delta, avoid visually oriented predators by hiding in sheltered, dark places where they discharge their
electric organs at a low and variable rate, interspersed with occasional short bursts (mean discharge rate, 4–12 Hz). Hence,
histograms of inter-discharge intervals (IDI) are broad and bimodal (IDI range, about 15–500 ms; “variable IDI pattern”).
We report here that with a female neighbor in electrical communication reach, captive males of M. altisambesi (N = 4) each showed a novel type of IDI resting pattern that was characterized by a higher and more constant discharge rate
(16–28 Hz). These IDI histograms were unimodal and narrow (IDI range, about 11–100 ms; “regularized IDI pattern”). In each
of these males, the regularized pattern vanished when the female neighbors were replaced by males, and the common variable
IDI pattern of low rate was observed instead. In an unforced choice paradigm, six M. altisambesi experimental females were allowed to choose between two electric fish decoys, one playing back the novel regularized IDI
pattern and one playing back the variable IDI pattern. Five experimental females significantly preferred staying close to
the decoy playing back the regularized IDI pattern, whereas one female showed the opposite preference. It appears that males
advertise to females during their diurnal period of overt inactivity, with an inconspicuous signal that neither threatens
conspecifics nor alerts predators by overt behavior. A secondary function of the regularized male IDI pattern could be to
advance the reproductive cycle of females. 相似文献
7.
A. Silva L. Quintana M. Galeano P. Errandonea O. Macadar 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(2):187-197
The mechanisms that trigger the onset of the breeding season depend on geographical latitude. At the edge of Gymnotiform
distribution in America, variations in day length and water temperature are likely cues to initiate breeding. In this study
we aim to clarify the role of temperature and the interaction between temperature and hormonal state upon electric organ discharge
waveform. In breeding ponds, we measured naturally occurring changes of water temperature and of electric organ discharge
waveform during two 48-h periods in a sample of identified mature males and females of Brachyhypopomus pinnicaudatus. Water temperature, day-night cycle, and sexual maturity each modified electric organ discharge waveform. Temperature sensitivity
was also evaluated in the laboratory in adult sexually-differentiated individuals, adult non-differentiated fish, juveniles,
and testosterone-treated fish. Our data strongly suggest an interaction between the effects of temperature and steroid hormones
upon electric organ discharge waveform. High temperature (30 °C) induced a significant decay of head negative phase amplitude
in temperature-sensitive fish. This sensitivity was observed in physiological conditions that coincide with low levels of
steroid hormones: juveniles and adult fish kept in captivity at 20–21 °C. Conversely, temperature resistance was observed
in mature fish in the breeding habitat and was induced by testosterone treatment and by captivity at 27–28 °C.
Accepted: 23 May 1999 相似文献
8.
The electric fish, Eigenmannia, will smoothly shift the frequency of its electric organ discharge away from an interfering electric signal. This shift in frequency is called the jamming avoidance response (JAR). In this article, we analyze the behavioral development of the JAR and the anatomical development of structures critical for the performance of the JAR. The JAR first appears when juvenile Eigenmannia are approximately 1 month old, at a total length of 13-18 mm. We have found that the establishment of much of the sensory periphery and of central connections precedes the onset of the JAR. We describe three aspects of the behavioral development of the JAR: (a) the onset and development of the behavior is closely correlated with size, not age; (b) the magnitude (in Hz) of the JAR increases with size until the juveniles display values within the adult range (10-20 Hz) at a total length of 25-30 mm; and (3) the JAR does not require prior experience or exposure to electrical signals. Raised in total electrical isolation from the egg stage, animals tested at a total length of 25 mm performed a correct JAR when first exposed to the stimulus. We examine the development of anatomical areas important for the performance of the JAR: the peripheral electrosensory system (mechano- and electroreceptors and peripheral nerves); and central electrosensory pathways and nuclei [the electrosensory lateral line lobe (ELL), the lateral lemniscus, the torus semicircularis, and the pace-maker nucleus]. The first recognizable structures in the developing electrosensory system are the peripheral neurites of the anterior lateral line nerve. The afferent nerves are established by day 2, which is prior to the formation of receptors in the epidermis. Thus, the neurites wait for their targets. This sequence of events suggests that receptor formation may be induced by innervation of primordial cells within the epidermis. Mechanoreceptors are first formed between day 3 and 4, while electroreceptors are first formed on day 7. Electroreceptor multiplication is observed for the first time at an age of 25 days and correlates with the onset of the JAR. The somata of the anterior lateral line nerve ganglion project afferents out to peripheral electroreceptors and also send axons centrally into the ELL. The first electroreceptive axons invade the ELL by day 6, and presumably a rough somatotopic organization and segmentation within the ELL may arise as early as day 7. Axonal projections from the ELL to the torus develop after day 18.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
9.
K. Suhasini A. P. Sagare K. V. Krishnamurthy 《In vitro cellular & developmental biology. Plant》1996,32(1):6-10
Summary Somatic embryos which originated from mature embryo axes of the chickpea (Cicer arietinum L.) showed varied morphologies. Embryos were classified based on shape of the embryo and number of cotyledons. “Normal” (zygotic-like)
embryos were bipolar structures with two cotyledons and a well-developed shoot and root apical meristem, whereas “aberrant”
embryos were horn-shaped, had single and multiple cotyledons, and were fasciated. Histological examination revealed the absence
of a shoot apical meristem in horn-shaped embryos. Fasciated embryos showed diaxial fusion of two embryos. Secondary embryogenesis
was also observed, in which the embryos emerged from the hypocotyl and cotyledonary region of the primary somatic embryo.
This report documents the absence of an apical meristem as a vital factor in the lack of conversion of aberrant somatic embryos. 相似文献
10.
Ravinder Kaur Grewal Monika Lulsdorf Janine Croser Sergio Ochatt Albert Vandenberg Thomas D. Warkentin 《Plant cell reports》2009,28(8):1289-1299
This is the first report on the production of double-haploid chickpea embryos and regenerated plants through anther culture
using Canadian cultivar CDC Xena (kabuli) and Australian cultivar Sonali (desi). Maximum anther induction rates were 69% for
Sonali and 63% for CDC Xena. Under optimal conditions, embryo formation occurred within 15–20 days of culture initiation with
2.3 embryos produced per anther for CDC Xena and 2.0 embryos per anther for Sonali. For anther induction, the following stress
treatments were used: (1) flower clusters were treated at 4°C for 4 days, (2) anthers were subjected to electric shock treatment
of three exponentially decaying pulses of 50–400 V with 25 μF capacitance and 25 Ω resistance, (3) anthers were centrifuged
at 168–1,509g for 2–15 min, and finally (4) anthers were cultured for 4 days in high-osmotic pressure (563 mmol) liquid medium. Anthers
were then transferred to a solid embryo development medium and, 15–20 days later, embryo development was observed concomitant
with a small amount of callus growth of 0.1–3 mm. Anther-derived embryos were regenerated on plant regeneration medium. Electroporation
treatment of anthers enhanced root formation, which is often a major hurdle in legume regeneration protocols. Cytological
studies using DAPI staining showed a wide range of ploidy levels from haploid to tetraploid in 10–30-day-old calli. Flow cytometric
analysis of calli, embryos and regenerated plants showed haploid profiles and/or spontaneous doubling of the chromosomes during
early regeneration stages. 相似文献
11.
Gerhard von der Emde Horst Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,171(5):683-694
Summary
Gnathonemus petersii discriminates between ohmic and capacitive objects. To investigate the sensory basis of this discrimination we recorded from primary afférents that innervate either A or B mormyromast sensory cells. Modified and natural electric organ discharges were used as stimuli. In both A and B fibres frequencies below the peak-power frequency (3.8 to 4.5 kHz) of the electric organ discharge caused minimal first-spike latencies and a maximum number of spikes. A fibres did not discriminate phase-shifted stimuli, whereas B fibres responded significantly with a decrease in first-spike latency if the phase shift was only — 1°. In both A and B fibres an amplitude increase caused a decrease in spike latency and an increase in spike number; an amplitude decrease had the reverse effect. If stimulated with quasi-natural electric organ discharges distorted by capacitive objects, the responses of A fibres decreased with increasing signal distortion. In contrast, the responses of B fibres increased until amplitude effects began to dominate. Gnathonemus may use the physiological differences between A and B fibres to detect and discriminate between capacitive and purely ohmic objects.Abbreviations ELL
electrosensory lateral line lobe
- EOD
electric organ discharge
- LFS
local filtered signal
- p-p
peak-to-peak 相似文献
12.
The influence of pollen irradiation on the production of in vitro haploid plants from in situ induced haploid embryos was
investigated in winter squash (Cucurbita maxima Duchesne ex Lam.). Pollen were irradiated at different gamma-ray doses (50, 100, 200 and 300 Gray) and durations (9, 11,
15, 21, and 28 July). Production of in vitro haploid plantlets was influenced by irradiation dose, irradiation duration, genotype,
and embryo type and embryo stage. Embryos were only obtained from lower irradiation doses (50 Gray and 100 Gray) and earlier
irradiation durations (9, 11, and 15 July). The greatest embryo number per fruit was procured from “G14” and “55SI06” genotypes
at 50 Gray gamma-ray dose. Necrotic embryos were higher than normal embryos at delayed harvest times (5 and 6 weeks after
the pollination). The convenient harvest time for embryo rescue was observed about 4 weeks (between 25 and 30 days) after
pollination. All cotyledon and amorphous embryos had only diploid plants while late-torpedo, arrow-tip, and pro-cotyledon
embryos produced 33.3, 50.0, and 66.7% haploid plant. The frequency of haploid plantlets was 0.11, 1.17, 10.96 and 0.28 per
100 seeds, 100 embryos, 100 plantlets and a fruit at 50 Gray gamma-ray dose, respectively. 相似文献
13.
Mary Hagedorn Heinrich A. Vischer Walter Heiligenberg 《Developmental neurobiology》1992,23(10):1446-1466
The electric fish, Eigenmannia, will smoothly shift the frequency of its electric organ discharge away from an interfering electric signal. This shift in frequency is called the jamming avoidance response (JAR). In this article, we analyze the behavioral development of the JAR and the anatomical development of structures critical for the performance of the JAR. The JAR first appears when juvenile Eigenmannia are approximately 1 month old, at a total length of 13–18 mm. We have found that the establishment of much of the sensory periphery and of central connections precedes the onset of the JAR. We describe three aspects of the behavioral development of the JAR: (a) the onset and development of the behavior is closely correlated with size, not age; (b) the magnitude (in Hz) of the JAR increases with size until the juveniles display values within the adult range (10–20 Hz) at a total length of 25–30 mm; and (3) the JAR does not require prior experience or exposure to electrical signals. Raised in total electrical isolation from the egg stage, animals tested at a total length of 25 mm performed a correct JAR when first exposed to the stimulus. We examine the development of anatomical areas important for the performance of the JAR: the peripheral electrosensory system (mechano- and electroreceptors and peripheral nerves); and central electrosensory pathways and nuclei [the electrosensory lateral line lobe (ELL), the lateral lemniscus, the torus semicircularis, and the pacemaker nucleus]. The first recognizable structures in the developing electrosensory system are the peripheral neurites of the anterior lateral line nerve. The afferent nerves are established by day 2, which is prior to the formation of receptors in the epidermis. Thus, the neurites wait for their targets. This sequence of events suggests that receptor formation may be induced by innervation of primordial cells within the epidermis. Mechanoreceptors are first formed between day 3 and 4, while electroreceptors are first formed on day 7. Electroreceptor multiplication is observed for the first time at an age of 25 days and correlates with the onset of the JAR. The somata of the anterior lateral line nerve ganglion project afferents out to peripheral electroreceptors and also send axons centrally into the ELL. The first electroreceptive axons invade the ELL by day 6, and presumably a rough somatotopic organization and segmentation within the ELL may arise as early as day 7. Axonal projections from the ELL to the torus develop after day 18. Within the torus semicircularis, giant cells are necessary for the performance of the JAR. Giant cell numbers increase exponentially during development and the onset of the JAR coincides with a minimum of at least 150 giant cells and the attainment of a total length of at least 15 mm and at least 150 giant cells. Pacemaker and relay cells comprise the adult Eigenmannia pacemaker nucleus. The growth and differentiation of these cell types also correlates with the onset of the JAR in developing animals. We describe a gradual improvement of sensory abilities, as opposed to an explosive onset of the mature JAR. We further suggest that this may be a rule common in most developing behavioral systems. © 1992 John Wiley & Sons, Inc. 相似文献
14.
Somatic embryogenesis in soybean via somatic embryo cycling 总被引:4,自引:0,他引:4
Wennuan Liu Patricia J. Moore Glenn B. Collins 《In vitro cellular & developmental biology. Plant》1992,28(3):153-160
Summary The objectives of the present research were: a) to develop an efficient soybean embryogenic regeneration system characterized
by a high frequency of explant response and a large number of somatic embryos per explant; b) to evaluate the factors affecting
somatic embryogenesis via somatic embryo cycling; and c) to identify the origin of somatic embryos in the system. A highly
improved and efficient system for soybean somatic embryogenesis was established using somatic embryo cotyledons and somatic
embryo hypocotyl/radicle explants plated on α-naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D) supplemented
MS basal media. The system included somatic embryo cycling between liquid and solid medium and it consistently gave rise to
a much higher frequency of explant response and a larger number of embryos per responding explant than those obtained from
zygotic cotyledon explant tissues. Genotype, differences were observed for response in some of the treatments with cv “Fayette”
being more responsive than “J103”. Histological studies revealed that somatic embryos induced in the somatic embryo cycling
system originated almost exclusively from epidermal cells on both 2,4-D and NAA inductive media. The cells of the epidermis
proliferated to produce somatic embryos directly without an intervening callus phase. A single-cell origin of somatic embryos
was observed in cultures on a 40 mg/liter 2,4-D treatment. A large number of responding cells in the epidermis was also observed
in the 10 mg/liter NAA treatment. The single-cell origin of somatic embryos from epidermal layers of the explant tissues should
facilitate development of an efficient transformation system for soybean. 相似文献
15.
Dormancy removal in apple embryos by nitric oxide or cyanide involves modifications in ethylene biosynthetic pathway 总被引:1,自引:0,他引:1
The connection between classical phytohormone-ethylene and two signaling molecules, nitric oxide (NO) and hydrogen cyanide
(HCN), was investigated in dormancy removal and germination “sensu stricto” of apple (Malus domestica Borkh.) embryos. Deep dormancy of apple embryos was removed by short-term (3–6 h) pre-treatment with NO or HCN. NO- or HCN-mediated
stimulation of germination was associated with enhanced emission of ethylene by the embryos, coupled with transient increase
in ROS concentration in embryos. Ethylene vapors stimulated germination of dormant apple embryos and eliminated morphological
anomalies characteristic for young seedlings developed from dormant embryos. Inhibitors of ethylene receptors completely impeded
beneficial effect of NO and HCN on embryo germination. NO- and HCN-induced ethylene emission by apple embryo was only slightly
reduced by inhibitor of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity during first 4 days of germination. Short-term pre-treatment of
the embryos with NO and HCN modified activity of both key enzymes of ethylene biosynthetic pathway: ACC synthase and ACC oxidase.
Activity of ACC synthase declined during first 4 days of germination, while activity of ACC oxidase increased markedly at
that time. Additional experiments point to non-enzymatic conversion of ACC to ethylene in the presence of ROS (H2O2). The results indicate that NO and HCN may alleviate dormancy of apple embryos “via” transient accumulation of ROS, leading
to enhanced ethylene emission which is required to terminate germination “sensu stricto”. Therefore, ethylene seems to be
a trigger factor in control of apple embryo dormancy removal and germination. 相似文献
16.
Interactions of varying ancymidol concentrations with those of α-naphthaleneacetic acid (NAA) or sucrose in embryo induction medium were related to the production and development of asparagus
(Asparagus officinalis L.) somatic embryos, and to the ability of these embryos to germinate. A significant sucrose×ancymidol interaction was observed
only for the production of bipolar embryos; 4% sucrose with 0.75 mg l–1 ancymidol gave the best result, 78 g–1 callus. The frequency of globular embryos decreased as sucrose or ancymidol concentrations increased. Sucrose concentration
affected embryo germination; 3% and 4% sucrose were optimal with approximately 60% and 40% of bipolar and globular embryos
germinating, respectively. Significant ancymidol×NAA interactions were observed for the production of bipolar and globular
embryos and their germination. Varying ancymidol concentrations affected embryo production and germination in combination
with 0.1 mg l–1 NAA, but not with 1.0 mg l–1 NAA. The treatment combination of 0.1 mg l–1 NAA with 0.75 mg l–1 ancymidol produced the most bipolar embryos, 64 g–1 callus, and the greatest percentages of bipolar and globular embryos germinated, 63% and 42%, respectively.
Received: 19 August 1996 / Revision received: 24 April 1997 / Accepted: 22 May 1997 相似文献
17.
S. B. Thencane S. R. Deodhar S. V. Bhosle S. K. Rawal 《In vitro cellular & developmental biology. Plant》2006,42(3):256-261
Summary Immature seeds of Garcinia indica Choiss, were exeised from immature fruits and cultured on Lloyd and McCown (1980), woody plant medium (WPM) with different
combinations of auxins and cytokinins. Somatic embryos were obtained on the media supplemented with 6-benzy laminopurine (BA;
2.2–22.1 μM) alone or in combination with α-naphthalene acetic acid (NAA; 2.6 μM) with 80% frequency within a period of 2–3 wk. Subculture of embryos on medium containing BA (16.0 μM) supplemented with indole-3-acetic acid (IAA: 2.8–5.7 μM) and/or kinetin (4.6 μM) gave rise to clusters of secondary somatic embryos along with maturation of primary embryos. In subsequent subculture on
hormone-free half-strength WPM, the embryo clusters germinated with an increase in the number of secondary somatic embryos.
About 70% of somatic embryos germinated into complete plantlets, which were successfully established under greenhouse conditions. 相似文献
18.
Summary The effects of abscisic acid (ABA) (0, 0.09 μM, 0.19 μM, 0.28 μM, and 0.38 μM) or ancymidol (0, 0.98 μM, 1.95 μM, 2.93 μM, 3.90 μM) in embryo germination medium on the conversion of primary embryos to plantlets and secondary embryogenesis were evaluated
for asparagus. ABA and ancymidol each significantly enhanced both responses. ABA was more effective than ancymidol in promoting
the conversion of primary embryos to plantlets, while the converse was true for the production of secondary embryos. The most
effective treatments for embryo conversion were 0.19 and 0.28 μM ABA; 75–77% bipolar and 55–57% globular embryos converted to plantlets. For secondary embryogenesis, the most effective treatments
were 1.95 and 2.93 μM ancymidol; 99–101 and 84–86 somatic embryos were produced from 10 globular and 10 bipolar embryos, respectively. Bipolar
embryos generally converted to plantlets better than globular embryos, but more secondary embryos were produced from globular
embryos than from bipolar embryos in all treatments. ABA and ancymidol also affected the morphology of the plantlets produced.
The plantlets from the embryos incubated on the medium with ancymidol had strong and thick shoots and roots, while those on
the medium with ABA had long, thin shoots and short thin roots. 相似文献
19.
V. I. Minakov 《Plasma Physics Reports》2009,35(9):754-767
A new type of plasma electron-emitting source capable of increasing the temperature of plasma electrons behind the edge of
a stationary plasma thruster (SPT) to 7–15 eV has been developed and investigated experimentally. For the same parameters
of the main discharge, the thrust, the thrust efficiency, the mass use factor, and the lifetime of the “SPT anode unit-plasma
electron-emitting source” assembly are found to increase substantially as compared to a thruster equipped with a conventional
cathode compensator. Simultaneously, the neutral particle pressure required for the existence of self-consistent distributions
of the electric field and charged particle density in the drift space of the neutralized ion beam decreases appreciably. It
is shown that the volume of the region in which primary slow ions are produced increases with increasing ionization frequency.
Three additional channels for discharge control are implemented. The ranges in which the discharge parameters can be controlled
are extended. 相似文献
20.
S. R. Soffe 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):711-715
Young Xenopus tadpoles were used to test whether the pattern of discharge in specific sensory neurons can determine the motor response
of a whole animal. Young Xenopus tadpoles show two main rhythmic behaviours: swimming and struggling. Touch-sensitive skin sensory neurons in the spinal cord
of immobilised tadpoles were penetrated singly or in pairs using microelectrodes to allow precise control of their firing
patterns. A single impulse in one Rohon-Beard neuron (= light touch) could sometimes trigger “fictive” swimming. Two to six
impulses at 30–50 Hz (= a light stroke) reliably triggered fictive swimming. Neither stimulus evoked fictive struggling. Twenty-five
or more impulses at 30–50 Hz (= pressure) could evoke a pattern of rhythmic bursts, distinct from swimming and suitable to
drive slower, stronger movements. This pattern showed some or all the characteristics of “fictive” struggling. These results
demonstrate clearly that sensory neurons can determine the pattern of motor output simply by their pattern of discharge. This
provides a simple form of behavioural selection according to stimulus.
Accepted: 28 November 1996 相似文献