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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 66 (1986), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Blooms of Dianthus caryophyllus cv. Crowley Pink (carnations) were held under standard environmental conditions in a range of vase solutions. In the absence of preservative solution the senescence of the flower was characterized by a single sharp peak of ethylene production. Culture in preservative solution greatly extended the life of the bloom and also reduced the output of ethylene. In addition, there was great variability between individual blooms in the timing, the extent and the pattern of ethylene production. Instead of a single peak some blooms had two or even three small peaks which, in some cases, were separated by intervals of several days. Senescence of these flowers was also characteristic of blooms that were not producing ethylene in that the petals often did not inroll. Putrescine and spermidine, when added to the culture solutions, did not delay the onset of senescence, nor did they inhibit ethylene production. In fact, both additives resulted in the earlier production of ethylene and shorter longevity when applied in conjunction with preservatives. Their effects were similar, but less marked when they were applied alone. Although polyamines have been reported to delay senescence in a number of tissues, spermine and putrescine did not have a protective effect in carnation flowers; indeed, in some treatments they advanced senescence.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cucurbita pepo L. cv. Trailing Marrow is monoecious, bearing separate male and female flowers and the first functional flowers are usually male. Treatment with 300 ppm ethephon delayed and greatly reduced male flower production and also increased female flower numbers. When plants were sprayed with aminoethoxyvinylglycine (AVG) no female flowers were produced but male flower production was unaffected. Even when ethephon was applied to AVG-treated plants there was still complete inhibition of female flower production. Similarly, AVG-treated plants subsequently exposed to 4000 ppm ethylene for two days never produced female flowers. AVG inhibits the penultimate stage in ethylene biosynthesis i.e. immediately before 1-aminocyclopropane-1-carboxylic acid (ACC). Although spraying AVG-treated plants with ACC did not reverse the inhibition, application of ACC via a cut petiole for a 72 h period following AVG application did cause female flowers to form. The evidence indicates that ACC and not ethylene is the factor controlling female flower production in C. pepo.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 58 (1983), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The application of ethephon to a single leaf of Cucurbita pepo L. cv. Trailing Marrow plants caused a huge increase in ethylene production from the treated organ and an increased rate of ethylene production from other parts of the plant. These increases were particularly marked in the shoot apex and expanding leaf. Prior treatment with aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor, blocked the increased production of ethylene at sites distant from the point of ethephon application. This strongly suggests that the increased ethylene production at these distant sites is due to ethylene biosynthesis and not a result of the translocation of ethylene released by the breakdown of ethephon at the site of application. Assays of 1-aminocyclopropane-l-carboxylic acid (ACC), an ethylene precursor, showed that it increased substantially after ethephon application but was at undetectable levels in the presence of AVG. It is proposed that the application of ethephon stimulates ethylene biosynthesis, but that transport through the plants is effected by ACC which is then converted to ethylene at the shoot apex and leaves.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 25 (1971), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Quantitative studies of the translocation of radiocarbon from a young expanded leaf of two tall varieties (Improved Pilot and Thomas Laxton) and two dwarf varieties (Little Marvel and Meteor) of Pisum sativum showed that 40 to 45 per cent of the radiocarbon was exported from the 14CO2 treated leaf after 24 hours in all four varieties. Although substantial export to the upper shoot always occurred it was more marked in the two tall varieties. Pre-treatment with GA did not affect total fixation but increased total export from the 14CO2 treated leaf in cv. Meteor and decreased it in cv. Improved Pilot. GA had no effect on the translocation pattern in the tall plants but modified that of the dwarf plants to correspond to that found in the tall varieties.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 22 (1969), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Rooting is shown to occur in excised cotyledons of Sinapis alba when grown in petri dishes on moist filter paper. Cotyledons were excised at intervals from 6 hours after the start of imbibition, when they were yellow, unexpanded and enclosed within the testa, to 27 days after sowing when the cotyledons were green and fully expanded and on plants possessing up to 3 foliage leaves. Rooting generally began 5 or 6 days after excision and was completed dining the following 5 days. The age of cotyledons at t ho time of excision had three effects on rooting: the lag period be-fore rooting began and the period during which rooting took place both increased with age: but the most marked effect was on the total number of cotyledons which were able to form roots, which increased until cotyledon expansion was almost complete, then decreased as the mature cotyledons became older. Optimal rooting was shown by cotyledons detached 8 days alter sowing, when they were half expanded. At this age S5 % of them formed roots between 6 days and 8 days after excision.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 22 (1969), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Unequal two shoot systems of tall and dwarf varieties of Pisum sativum L. ev, Improved Pilot and Meteor, respectively, were used in experiments where manipulative treatments involving the removal of one or other or both of the shoot apices were carried out. These were combined with GA treatments. Twenty four hours after treatment, 14CO2 was applied to the lowest expanded leaf on the larger shoot, and the distribution of radioactivity was determined after a further 24 hours. Removal ot the apex of the larger shoot reduced the level of translocation from the treated leaf, the effect being enhanced by the additional removal of the other apex. This (Heel was more marked in the tall than in the dwarf variety.In untreated control plants of both varieties there was very little transfer ot labelled material from the larger (dominant) shoot to the smaller (weaker) shoot. This pattern was not affected by the removal of the apex from the weaker shoot. In Improved Pilot, removal of the apex from the stronger shoot led to considerable transfer of radioactive material to the weaker shoot, GA treatment having little effect. However, in Meteor, transfer of radioactivity from the stronger to the weaker shoot. after removal of the apex from the stronger shoot, only occurred after the application of GA. Removal of both shoot apices again resulted in low levels of transfer of labelled material to the weaker shoot in both varieties.These results are consistent with the hypothesis that there is competition between the two shoots for photosynthates produced by the leaves and that treatments reducing the competitive ability of one shoot, reduce the level of nutrients received by that shoot and can result in transfer of materials from it to the other shoot. Continuation of such a situation will result in increased inequality and perhaps ultimately in the death of the weaker shoot.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 23 (1970), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pods of Pisum sativum cv. Meteor were supplied with 14CO2 and the fixation and distribution of the radiocarbon studied. A high fixation rate was found in all of the treated pods. In intact control plants about 60 per cent of the total radiocarbon fixed was exported from the carpet into the seeds of the treated pod in the 24 hour period following fixation. Almost all of the remainder was relained in the carpel itself. It was found that the seeds in the treated pod were the major sink for these fixation products and that the weight of the seed determined the level of import of radiocarbon from the carpel in both attached and detached pods. Removal of the seeds from the treated pod prior to 14CO2 treatment reduced export from the fed carpel from 60 to 15 per cent, this being distributed mainly in the other pods and stem fractions. It appears that carpet photosynthate is likely to be of great importance in the growth and development of seeds enclosed by the carpel. control of fixation and export of radiocarbon seemed to be a function of the carpel and the seeds enclosed by the carpel and to be relatively independent of the rest of the plant. This could explain the absence of effect of GA on these processes.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 23 (1970), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: When localized areas of blades of recently excised mustard cotyledons were fed with 14CO2 it was found that the fixation products passed rapidly into the veins and then were translocated to the petiole. Since other cotyledons similarly treated subsequently rooted at the petiole base, this suggested that it acted as a sink for assimilates. Treatment of excised cotyledons with benzylaminopurine (BAP) resulted in the enhancement of blade growth and the suppression of root initiation and development. Quantitative determinations of labelled assimilate in both the cotyledon blade and the terminal 2 mm portion of the petiole were made. It was found that cotyledons treated with BAP at a concentration high enough to suppress completely root initiation had a higher level of radioactivity in the petiole base than the terminal segments in untreated petioles, whether expressed as specific activity or as a percentage of the total radiocarbon fixed. BAP-treated cotyledons also fixed consistently higher levels of 14CO2, probably due to an increase in photosynthetic area. The results suggest that BAP alters the pattern of differentiation at the base of the petiole rather than the polarity of movement of assimilates to the petiole base.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 61 (1984), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cuttings of Agathis australis (D. Don) Lindl passed through a well-defined series of morphological changes prior to root emergence. These phases were incorporated into a morphological index which can be used as a guide for the selection of cuttings at known developmental and anatomical stages. After a variable period (lag phase) during which no external change occurred there was an increase in stem diameter a few milimetres above the cut base. This swelling gradually increased in size and isolated bulges developed. Longitudinal splits then arose in the epidermis over the bulges, followed by root emergence through the splits. Root initiation occurred shortly after the sub-basal swelling commenced in cuttings that eventually rooted. Removal of the basal 8 mm of a rooted cutting (which included the roots) usually led to re-rooting of the cuttings. However, if the roots were merely trimmed off, the cutting never formed new roots and always died. The basal region apparently has the capacity to produce only one set of roots. Occasionally the stem diameter continued to increase and the swelling extended to include the basal region. Such cuttings never formed isolated wellings and never rooted.In general the younger the plant from which the cutting was taken, the shorter the lag phase and the higher the final percentage rooting. Cuttings taken from older plants had a lower rooting percentage and a more variable lag phase, which was related to the time of year the cuttings were taken since root emergence always occurred in spring. Irrespective of the age of the original material there was a constant time period (3–4 weeks) from root initiation to root emergence.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 23 (1970), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Senescence of detached mustard cotyledons was greatest in full light or at low light intensity but was reduced at intermediate light intensities. The location of yellowing in the blade depended on the conditions in which it was maintained after excision. Cotyledons cultured at full light intensity in the absence of exogenous nutrients formed roots at the base and yellowed around the margins. Reduction in light intensity and increasing nutrient concentrations resulted in an increasing proportion of the cotyledons yellowing from the base upwards, and fewer developed roots. At low light intensity with high nutrient levels rooting was suppressed and basal senescence predominated.The location of yellowing in the cotyledon may be associated with mobilisation gradients induced by the differential effects of light and mineral nutrient level on root initiation and blade growth.
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