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  • 1
    Electronic Resource
    Electronic Resource
    Seasonal dynamics of carbohydrate and nitrogenous components in the roots of perennial weeds (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Chicory (Cichorium intybus L.) and dandelion (Taraxacum officinale L.) are persistent weeds, the aerial portions of which do not survive in winter. However, subterranean tissues remain viable and facilitate the rapid resumption of growth in early spring. The source of nutrients for growth prior to the establishment of foliage is the roots. Carbohydrate and N reserves are accrued during late summer and autumn, respectively. Hydrolysis of fructans during late autumn occurs coincidentally with increments in sucrose, the latter providing a readily accessible C pool. Nitrate, free amino acids and soluble protein all play substantial roles in nitrogen storage. Asparagine is the predominant amino acid in the free pool during winter, followed by glutamine, ornithine, serine, aspartic acid and glutamic acid. Storage reserves remain at peak levels throughout winter and deeline prior to the resumption of growth. The patterns observed here provide evidence that N is an important currency of storage metabolism and, thus, a framework has been provided for the examination of regulation of N storage in perennial weeds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1990.tb02139.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of temperature and moisture stress on the accumulation of abscisic acid in bean (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 58 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Levels of abscisic acid (ABA) and several indicators of leaf-water status were measured in excised and intact primary leaves of bean (Phaseolus vulgaris cv. Kinghorn) exposed to different temperature and moisture regimes. After 2 h at 5°, 25° or 45°C under moist conditions, the water status of detached leaves showed only minor changes, and there was no increase in ABA. Under conditions favoring water loss, ABA rose over 10-fold at 25°C, and trends towards higher ABA levels were observed at 5° and 45°C. When intact leaves on whole plants were exposed to the same temperatures for 10 h, there was still no evidence of a temperature-dependent rise in ABA that was not associated with a disturbance in the water balance of the plant. These data suggest that the rapid accumulation of ABA during temperature stress is a function of induced moisture deficits and does not result from high or low temperatures per se.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb04165.x
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  • 3
    Electronic Resource
    Electronic Resource
    Seasonal Levels of Abscisic Acid in Buds and Stems of Acer saccharum (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 45 (1979), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in abscisic acid (ABA) were followed in the buds and youngest stems of 6-year-old sugar maple (Acer saccharum Marsh.) saplings at approximately monthly intervals during the year. High levels present in the buds in July and August showed a moderate decline through early October, but subsequently increased following leaf fall and reached the maximum values detected during the study in November and December. Thereafter ABA fell sharply, reaching its lowest point immediately prior to budbreak in early May. While ABA in the stems followed a somewhat similar pattern, only minor changes were observed in the relatively low values detected between June and November. Except for the spring months, when concentrations of ABA in the stems and buds were at minimum levels, the buds always contained several times more inhibitor per unit dry weight of tissue. Analysis of selected samples from both tissues showed that bound (alkaline-hydrolyzable) ABA increased during the overwintering season, with the highest values noted in the spring. Although the patterns of change observed in this study are indicative of a role for ABA in the overwintering process, ABA does not appear to be the primary endogenous factor responsible for initiation of the dormant state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1979.tb01689.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of moisture stress and senescence on the synthesis of abscisic acid in the primary leaves of bean (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 51 (1981), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The capacity for ABA synthesis during moisture stress of primary leaves of bean (Phaseolus vulgaris cv. Kinghorn) was defined in terms of leaf age and associated changes in several physiological parameters. The leaves were fully expanded within 9 days after emergence. Fresh and dry weights per unit of leaf area fell during all 5 weeks of the study, from leaf expansion through advanced senescence. The most significant losses in weight occurred during the third and fourth weeks and coincided with a sharp drop in protein content that began immediately after full-leaf. Chlorophyll concentrations declined rapidly during leaf expansion and then more slowly through the end of the fifth week when the leaves were ready to abscise. The ratio of chlorophyll a to b rose steeply over the first 4 weeks of the study.Although a rapid loss of protein provided the most definitive indication of the early stages of leaf senescence, a marked decline in the ability to synthesize ABA was more closely associated with the termination of rapid leaf growth. This relationship between leaf expansion and the capacity for ABA synthesis during moisture stress remained unchanged when ABA content was expressed on a per unit chlorophyll, protein or dry weight basis.A water deficit between 5 and 10% of fresh weight, representing a drop in water potential of less than 150 kPa, was sufficient to initiate accumulation of ABA in young leaves. Slightly more intensive levels of stress were required to stimulate ABA synthesis in senescent leaves, but total accumulation was less than one-tenth of the amount recorded in the younger tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1981.tb05579.x
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  • 5
    Electronic Resource
    Electronic Resource
    In vitro evidence for the involvement of activated oxygen in light-induced aggregation of thylakoid proteins (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 82 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Protein aggregation in thylakoids incurred in situ during light-induced heat shock damage can be simulated in vitro by illuminating isolated thylakoids at normal temperatures. Aggregation is detectable in the in vitro model system by fluorography of [35-S]-methionine-labelled thylakoids fractionated by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and also by Coomassie staining after SDS-PAGE of unlabelled thylakoids. As in the case of light-induced heat shock damage, protein aggregation in the in vitro system is completely light dependent, and the D-1 protein of PS][is present in the protein aggregate. The model system has also provided evidence for the involvement of activated oxygen in aggregation of thylakoid proteins. Histidine, which scavenges singlet oxygen, and n-propylgallate; a non-specific scavenger of activated oxygen, both provided complete protection against light induced protein aggregation in isolated thylakoids. These compounds also strongly reduced the levels of activated oxygen by illuminated thylakoids as measured by electron spin resonance. The involvement of activated oxygen is further supported by the finding that protein aggregation in the model system proved to be oxygen dependent. The herbicide dichlorophenyldimethyl urea, which binds to the QB site of the D-1 protein of PSII and provides protection against photoinhibition and light dependent degradation of the D-1 protein, also provided partial protection against protein aggregation in the in vitro system. Protein continues to aggregate after PSII activity has reached undetectable levels suggesting that aggregation is a consequence rather than a cause of photoinhibition. The observations collectively indicate that aggregation of thylakoid proteins is attributable to activated oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb02922.x
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  • 6
    Electronic Resource
    Electronic Resource
    Triadimefon stimulates rooting in bean hypocotyl (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 73 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Triadimefon, a broad spectrum fungicide and an inhibitor of gibberellic biosynthesis, whitened, thickened, and shortened the roots of bean (Phaseolus vulgaris L. cv. Spring Green) seedlings and stimulated the development of root primordia along the hypocotyl. In a comparative study, triadimefon, IAA, spermidine, putrescine and spermine all stimulated adventitious root growth, but triadimefon was more effective than the other 4 compounds. Equimolar concentrations of gibberellic acid (GA3) completely eliminated the stimulatory effect of triadimefon. Stimulation of root development by triadimefon was accompanied by inhibition of ethylene biosynthesis followed by removal of basal dominance and an increase in polyamine levels, both of which occurred after rooting had begun. Although triadimefon was effective in stimulating rooting, its mechanism of action is apparently not mediated via the control of ethylene and polyamine biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb00617.x
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  • 7
    Electronic Resource
    Electronic Resource
    Senescence in cut carnation flowers: Temporal and physiological relationships among water status, ethylene, abscisic acid and membrane permeability (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 68 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in water status, membrane permeability, ethylene production and levels of abscisic acid (ABA) were measured during senescence of cut carnation flowers (Dianthus caryophyllus L. cv. White Sim) in order to clarify the temporal sequence of physiological events during this post-harvest period. Ethylene production and ABA content of the petal tissue rose essentially in parallel during natural senescence and after treatment of young flowers with exogenous ethylene, indicating that their syntheses are not widely separated in time. However, solute leakage, reflecting membrane deterioration, was apparent well before the natural rise in ethylene and ABA had begun. In addition, there were marked changes in water status of the tissue, including losses in water potential (ψw), and turgor (ψp), that preceded the rise in ABA and ethylene. As senescence progressed, ψw continued to decline, but ψp returned to normal levels. These temporal relationships were less well resolved when senescence of young flowers was induced by treatment with ethylene, presumably because the time-scale had been shortened. Thus changes in membrane permeability and an associated water stress in petal tissue appear to be earlier symptoms of flower senescence than the rises in ABA or ethylene. These observations support the contention that the climacteric-like rise in ethylene production is not the initial or primary event of senescence and that the rise in ABA titre may simply be a response to changes in water status.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb01934.x
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  • 8
    Electronic Resource
    Electronic Resource
    Exogenous polyamines alter membrane fluidity in bean leaves — a basis for potential misinterpretation of their true physiological role (1986)
    Springer
    Planta 167 (1986), S. 395-401 
    Details
    ISSN: 1432-2048
    Keywords: Membrane fluidity ; Phaseolus (polyamine effects) ; Polyamine ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the rotational motion of paramagnetic and fluorescent lipid-soluble probes were used to assess the effects of putrescine, spermidine and spermine on the fluidity of microsomal membranes from primary leaves of bean (Phaseolus vulgaris L.). Surface probes were more strongly immobilized by physiological concentrations of the polyamines than probes that partitioned deep into the bilayer interior. Spermidine and spermine were more effective than putrescine at reducing membrane fluidity, and at equimolar concentrations, the polyamines and calcium had similar effects on the mobility of the membrane probes. Spermine had essentially equivalent effects on the fluidity of native membranes, heat-denatured membranes and liposomes prepared from the total lipid extract of the membranes, indicating that polyamines associate with membrane lipid. These results raise the possibility that some of the physiological effects previously attributed to exogenously added polyamines could reflect membrane rigidification rather than a true physiological response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391345
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and oxidative insolubilization of cell-wall proteins during osmotic stress (1999)
    Springer
    Planta 208 (1999), S. 401-408 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Cell wall ; Osmotic stress ; Oxidative insolubilization ; Pinus (root turgor) ; Root polypeptides ; Turgor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The cell walls in the new white roots of jack pine (Pinus banksiana Lamb.) were observed to constrict around the shrinking protoplast of osmotically stressed roots, and pressure was maintained via an apparent adjustment of cell-wall size and elasticity. These elastic alterations of the cell wall permitted the root cells to maintain full turgor despite the loss of most of the water in the tissue. The constriction of the root cell wall around the dehydrating protoplasts to maintain turgor may reflect changes in cell wall structure. We found that these shrinking root cells synthesize and secrete into the intercellular fluid a set of proteins. These proteins become tightly associated (i.e. guanidine HCl- and sodium dodecyl sulfate-insoluble) with the cell wall but can be released from the matrix, after briefly boiling in 0.1% sodium dodecyl sulfate, by the combination of guanidine HCl, CaCl2 and dithiothreitol. However, these cell-wall proteins became insoluble with time. The proteins could subsequently be destructively extracted from the wall with acid NaClO2 treatments. After these proteins were incorporated into the cell walls, the roots adopted a new, smaller maximal tissue volume and elastic coefficients returned to normal levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050575
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  • 10
    Electronic Resource
    Electronic Resource
    Microbial responses to salt-induced osmotic stress (1984)
    Springer
    Plant and soil 80 (1984), S. 363-371 
    Details
    ISSN: 1573-5036
    Keywords: Fluorescence microscopy ; Exudates ; Microbial ecology ; Model root ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The construction and assembly of a model root region is described. The model was used to manipulate the soil matrix, soil microorganisms, and to simulate release of root exudates. The design of the apparatus facilitated long-term, direct microscopic observations of microbial activity in soil and on artificial roots. Preliminary studies indicate that microbial responses to osmotic stress and to changes in components of exudate solutions are easily monitored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02140043
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