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131.
C. T. Phan 《Plant cell reports》1991,9(9):517-519
The occurrence of a developmental anomaly i in vitro culture, named vitreous plant, has been shown to be a deficiency in lignification. Several causes have been proposed, most recently the physical state of the culture medium and ethylene. Experiments, conducted to verify these suggestions, led toresults that did not confirm either the physical state or ethylene as causal agents. It rather appeared that cytokinins did induce the anomaly, probably by excessively promoting cell-divisions at the expense of cell-differentiation. 相似文献
132.
Primary explants of Picea abies (L.) Karst. and Pinus sylvestris L. were incubated for various periods in solutions containing different concentrations of [14 C]-benzyladenine. Time course analysis showed that uptake was linear for the initial 60 min; after this time linear uptake continued but at a much reduced rate. The amount of benzyladenine taken up by the explants saturated at a concentration about one third of that of the medium, Concentration dependence experiments showed that BA uptake was directly proportional to the external concentration. These results and those from experiments in which uptake was examined at different temperatures are consistent with a passive mode of BA uptake. The results are discussed with respect to in vitro micropropagation. 相似文献
133.
Plant growth substances (PGSs) were analysed in liquid endosperm of black walnut using HPLC and an ELISA procedure. Of all the PGSs studied, we show no GA3, low levels of cytokinins (io6A, i6Ade, i6Ado) and ABA, and very high level of IAAAbbreviations ABA
Abscisic acid:
- Ade
Adenine:
- GA3
Gibberellic acid:
- IAA
Indole-3-acetic acid:
- i6Ade
N6(2-1) adenine:
- i6Ado
N6(2-isopentenyl adenosine:
- io6A
Zeatin riboside: 相似文献
134.
135.
Grand Rapids lettuce (Lactuca sativa L.) seeds were stored in an imbibed state for up to two years. Embryos dissected from stored seeds showed a progressive loss with time in their ability to germinate on polyethylene glycol (PEG) solutions. Little germination of dissected embryos from one-month imbibed seeds occurred on-6 bar PEG but only after four months of storage did the dissected embryos fail to germinate on-4 bar PEG. After two years storage 30% of dissected embryos still were able to germinate on-2 bar PEG. This loss of germination potential, which may be a symptom of the development of an embryo dormancy, could be reversed by N6-benzyladenine (BA) and red light (R) applied together or separately to dissected embryos. Two weeks of chilling of 12-month imbibed seeds restored sensitivity to R and a 48-h BA pretreatment prior to R resulted in germination rates similar to those of seeds emerging from primary dormancy. There was loss of embryo control of endo--mannanase activity after two weeks of storage even though the endosperms themselves retained their capacity for enzyme synthesis for six more weeks. Eventually, then, endo--mannanase synthesis is not possible because of inherent changes in both the embryo and endosperm, although each tissue undergoes changes at its own rate. Oxygen uptake by embryos dissected from two-month imbibed seeds did not increase to the same extent as embryos dissected from freshly imbibed seeds. In intact seeds germinating from a skotodormant state, oxygen uptake increased at a time coincident with radicle protrusion, but did not achieve the levels of uptake of those seeds germinating from a primary dormant state. The decline in uptake of oxygen by secondary dormant seeds is the result of a lowered respiratory capability of the embryo itself, rather than of changes in permeability of the surrounding structures.Abbreviations BA
N6-benzyladenine
- Pfr
active (far-redabsorbing) form of phytochrome
- R
red light
- PEG
polyethylene glycol 相似文献
136.
The maintenance of species-specific behavioural repertoires and traditions is an important but often implicit goal of conservation efforts. When captive rearing is used as a conservation practice, it becomes critical to address its possible implications for the social and behavioural traits of developing individuals. In particular, animals must retain or acquire many of their behavioural abilities to increase the likelihood of survival upon release into the wild. This study investigated the behavioural development of critically endangered kaki (black stilt: Himantopus novaezelandiae ) chicks reared without live adult conspecifics. The captive rearing programme included playbacks of adult kaki alarm calls during cleaning and handling of precocial chicks housed as groups. We used videotaped observations and playback experiments to address the following questions: do kaki chicks respond differentially to (1) familiar versus unfamiliar adult kaki alarm calls and (2) conspecific alarm versus heterospecific control vocalizations. Adult-naïve kaki chicks exhibited a varied behavioural repertoire over their early development. In multivariate analyses, when age was statistically controlled, chicks showed responses to familiar and unfamiliar alarm calls that were similar in magnitude. In contrast, following conspecific alarm calls chicks had longer average latencies to resume pre-playback activities than following heterospecific vocalizations. Although the generality of these conclusions is limited by experimental constraints stemming from working with an endangered species, the findings suggest that current management techniques produce captive-reared kaki for release into the wild that possess many of the behavioural and auditory recognition skills that are required for survival. 相似文献
137.
Roger Guevara 《Biotropica》2011,43(1):122-130
For all its positive attributes, the recent expansion of ecotourism has resulted in greater influxes of people into natural areas, causing a range of impacts including behavioral disruptions among wildlife. How animals respond to conversation is poorly understood, but noise reduction may reduce the impact of ecotourists while simultaneously enhancing their experience with higher wildlife encounter rates. We tested the response of a rain forest bird community to noise by playing a recorded conversation while conducting point censuses in a terra firme forest in Tambopata, Peru. Fifty decibel conversation (approximately library speaking volume) caused declines of 35 percent in total detections and 33 percent in detected species richness. Birds reacted similarly to 60 dB (approximately the volume of an excited child): average detections declined by 39 percent and detected species richness by 37 percent. Specifically, noise‐induced detection declines were manifest both in decreased vocalizations (37% decline) and decreased physical sightings (44% decline). Lowered detection frequencies indicate behavioral shifts. As vocalization is involved in territory defense, breeding behavior, and predator detection, strong noise responsiveness indicates potential harm for birds. Insectivores were the most affected bird guild, raising conservation concerns, as insectivorous birds are sensitive to habitat modification. Birds reacted strongly to noise both near an established ecotourist lodge and in an intact reserve, indicating an absence of habituation. Thus, as a method for reducing ecotourism's footprint on native fauna and improving tourist satisfaction with increased wildlife sightings, noise reduction seems promising, even for well‐established ecotourist lodges. 相似文献
138.
Pascal Lambé Hity Schié Nkung Mutambel Jean-Gabriel Fouché Roger Deltour Jean-Michel Foidart Thomas Gaspar 《In vitro cellular & developmental biology. Plant》1997,33(3):155-162
Summary Progressive loss of organogenic totipotency appears to be a common event in long-term plant tissue culture. This loss of totipotency,
which has been proposed to be a typical trait of plant neoplastic progression, is compared to some mechanisms that occur during
the establishment of animal differentiation-resistant cancer lines in vitro. Evidence is presented that alteration in DNA methylation patterns and expression of genes occur during long-term callus
culture. An effect of the auxin, 2,4-dichlorophenoxyacetic acid, in the progressive methylation, is moreover suggested. Methylation
of genes relevant to cell differentiation and progressive elimination of cells capable of differentiation is proposed as being
responsible for this progressive loss of organogenic potential. Finally, the epigenetic alteration (DNA methylation) that
occurs during prolonged periods of culture may induce other irreversible genetic alterations that ultimately make the loss
of totipotency irreversible. 相似文献
139.
Two pairs of harbor ( Phoca vitulina ) and three pairs of gray ( Halicboeruls grypus ) seals were exposed to one of three human handlers for 15 min, twice a day, for a total of six sessions. Following habituation to the familiar handler, animals were then exposed to a novel human for 7 min, and then retested for 7 min with the familiar human. In all cases, animals responded to the unfamiliar human with increased vigilant behavior, i. e., they spent more time oriented towards the unfamiliar handler during the first 2 min of the test session than during the same interval of either the final habituation session or the retest with the familiar human ( P = 0.03 in all cases). There was also a tendency for seals to contact the familiar handler with their noses more rapidly than the novel human ( P = 0.06). These results support the hypothesis that phocid seals are capable of discriminating between individual humans in their environment, setting the stage for human-based Pavlovian conditioning. 相似文献
140.
Zeatin is a highly active and ubiquitous cytokinin. O-Glycosylation of zeatin occurs widely in plant tissues and is likely to be important in regulating the level of active cytokinins. Enzymes mediating the conversion of zeatin to O-glucosylzeatin and O-xylosylzeatin have been isolated from Phaseolus seeds. The corresponding genes have been cloned recently. The current status of molecular and biochemical studies of these genes and enzymes is summarised in this paper. 相似文献