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  • 1
    Electronic Resource
    Electronic Resource
    Occurrence of hydroxylated jasmonic acids in leaflets of Solanum demissum plants grown under long- and short-day conditions (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 88 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Under short-day (SD) conditions both 11-OH-jasmonic acid (11-OH-JA) and a smaller quantity of 12-OH-JA occurred in leaflets of Solanum demissum Lindl. Plants which had formed tubers. This is the first time that 11-OH-JA has been detected as a native substance in higher plants. Under long-day (LD) conditions no tubers were formed and none of these compounds were detectable. A positive correlation was found between the occurrence of 11-OH-JA and 12-OH-JA in leaflets of S. demissum and tuber formation, but a causal relation has yet to be proved. The (-)-JA content in leaflets was not significantly different under short and long days. Mild stress applied to detached SD and LD leaflets caused a rapid accumulation of JA in these leaflets. Upon this treatment an increase in the levels of hydroxylated JAs was detected in SD leaflets only.JA was a potent promotor of tuber formation in vitro in S. demissum explants. Lipoxygenase (LOX: EC 1.13.11.12) is involved in the biosynthesis of JA. Under SD conditions, application of salicylhydroxamic acid (SHAM), an inhibitor of LOX activity, to the roots did not prevent tuber formation in vivo. It is suggested that daylength controls the hydroxylation of JA. The enzyme(s), responsible for the hydroxylation of JA, would only be effective under SD conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb01384.x
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  • 2
    Electronic Resource
    Electronic Resource
    Uptake of 13C-glucose by cell suspensions of carrot (Daucus carota) measured by in vivo NMR: Cycling of triose-, pentose- and hexose-phosphates (2000)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 108 (2000), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: After a lag phase of 2 days, batch-grown cells of carrot (Daucus carota L.) cv. Flakkese entered the exponential growth phase and started to accumulate sucrose and hexoses. Short-term feeding 13C-glucose in this period resulted in only minor labelling of sucrose or fructose. CO2 production from [1-13C]- and [6-13C]-glucose revealed, that at least 40% of the added glucose passed through the oxidative pentose phosphate pathway (OPPP), up to 40% through glycolysis leaving only minor 13C-glucose for incorporation in various cell components in the exponential growth phase. After about 11 days of culture, the medium sugars were exhausted, cells entered the stationary growth phase and consumed stored sugar. Both neutral and acid invertase (EC 3.2.1.26) and sucrose synthase (EC 2.4.1.13) increased 50% from day 0 to days 11–13; thereafter their levels decreased again. Labelling with 13C-glucose resulted in the accumulation of labelled sucrose and fructose during the stationary growth phase. Sucrose labelling was transient, i.e. after 6 h its level started to decrease again. Labelled fructose, however, evolved slower and increased even after 8 h. In sucrose and fructose up to 20% of the 13C-label was exchanged from C-1 to C-6 carbons, indicating intensive cycling of at least 40% of the carbon between hexoses and triose phosphates. In the stationary phase only 10% of the labelled glucose passed through the OPPP and about 30% passed through the respiratory pathway; the remaining 60% was incorporated in cell constituents and sugars. Comparing the various cycles revealed that the regulation of the OPPP operated relatively independently from the cytosolic cycling of hexose phosphates through sucrose and from the cycling between hexose phosphates and triose phosphates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.108002125.x
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  • 3
    Electronic Resource
    Electronic Resource
    In situ analysis of enzymes involved in sucrose to hexose-phosphate conversion during stolon-to-tuber transition of potato (2002)
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 115 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An in situ study of enzymes involved in sucrose to hexose-phosphate conversion during in vitro stolon-to-tuber transition of potato (Solanum tuberosum L. cv. Bintje) was employed to follow developmental changes in spatial patterns. In situ activity of the respective enzymes was visualized by specific activity-staining techniques and they revealed distinct spatially and developmentally regulated patterns. Two of the enzymes studied were also subject to in situ investigations at the transcriptional level. During the stages of stolon formation high hexokinase (EC 2.7.1.1) and acid (cell wall-bound) invertase (EC 3.2.1.26) activities were restricted to the mitotically active (sub)apical region, suggesting a possible importance of these enzymes for cell division. At the onset of tuberization sucrose synthase (EC 2.4.1.13) and fructokinase (EC 2.7.1.4) were strongly induced (visualized at transcriptional and translational level) and the acid invertase activities disappeared from the swelling subapical region as expected. The high degree of similarity in the spatial pattern and the temporal induction of sucrose synthase and fructokinase suggests a tightly co-ordinated coarse (up)regulation, which may be subject to a sugar-modulated mechanism(s) by which genes involved in the metabolic sucrose-starch converting potential are co-ordinately regulated during tuber growth. The overall activity of uridine-5-diphosphoglucose pyrophosphorylase (EC 2.7.7.9) was present in all tissues during stolon and tuber development, implying that its coarse control is not subject to (in)direct developmental regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1150218.x
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  • 4
    Electronic Resource
    Electronic Resource
    Tuber morphology and starch accumulation are independent phenomena: Evidence from ipt-transgenic potato lines (2000)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 108 (2000), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tuber formation and carbohydrate metabolism in potatoes were studied using transgenic potato plants carrying the Agrobacterium tumefaciensipt gene, involved in cytokinin biosynthesis. Three independent transformants, viz. clones 1, 11 and 13, whose cytokinin and auxin content had previously been shown to be different from each other and from the wild-type, were analysed in vitro. Clones 11 and 13 showed a higher ability to form stolons and tubers, as evident from: (1) stolon development in whole plants grown under non-inductive conditions, (2) total number and weight of tubers formed by cuttings of this clone in darkness, (3) tubers appeared earlier than tubers of wild-type plants and at a lower sucrose concentration in the medium. Clone 1 did not form stolons or tubers under any conditions tested, but rather formed short shoots. A series of metabolic changes, known to be characteristic for tubers, were analysed in leaves, stems and developing buds. It was found that the short type of shoots, formed by clone 1, had metabolic characteristics very similar to tubers formed in wild-type or clones 11 and 13, including glucose, fructose, sucrose, and starch levels, and activities of invertase, sucrose synthase and fructokinase. It is concluded that the regulation of the stolon swelling and of carbohydrate metabolism, normally occurring simultaneously, can be uncoupled, and are thus, at least partly independent phenomena. The present data obtained with a high-cytokinin line indicate that cytokinins (probably in concert with auxins) might be mainly involved in the regulation of tuber morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.100414.x
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  • 5
    Electronic Resource
    Electronic Resource
    Gene expression and carbohydrate content during stolon to tuber transition in potatoes (Solanum tuberosum) (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 90 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In using an efficient and synchronised in vitro tuberisation system the transition of axillary buds from stolons to tubers in Solanum tuberosum L. cv. Bintje was followed. After 5 or 6 days on tuber-inducing medium all axillary buds had formed tubers which increased in size until the experiment was ended at day 10. Concomitantly with the visible appearance of tubers the fresh weight of the axillary buds increased as well as their starch content. Soluble sugar content, notably glucose, increased until tuberisation occurred and dropped after that. In the daily sampled explants gene expression was studied at several levels. RNA was isolated from the different explants during the whole tuberisation experiment and northern blots were probed with cDNAs encoding genes involved in starch- and patatin-biosynthesis. It was shown that in the very early stages of development hardly any transcript could be detected. Only one day before visible swelling occurred were clear signals obtained for all the genes investigated. Although it was evident that coordinate expression of starch biosynthetic genes did occur, it was not in a similar fashion for all the genes. Sucrose synthase and ADPG-pyrophosphorylase B were expressed in an identical fashion which was different from ADPG-pyrophosphorylase S, granule-bound starch synthase and branching enzyme. The RNA levels of these three latter genes reached a maximum at day 5, remaining constant until the experiment was finished. The transcript levels of sucrose synthase and ADPG-pyrophosphorylase B reached their highest level at day 5 after which they dropped to a lower level at day 10. Patatin gene expression was clearly different from that of the starch biosynthetic genes: it steadily increased from day 4 until the end of the experiment. Enzyme activities of sucrose synthase. ADPG-pyrophosphorylase and branching enzyme confirmed the RNA expression data and showed that ADPG-pyrophosphorylase enzyme activity reached a maximum at day 4 after which it dropped. The other two enzyme activities could be detected at or one day after tuberisation occurred and increased until the experiment was ended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb00389.x
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  • 6
    Electronic Resource
    Electronic Resource
    An integrated view of the hormonal regulation of tuber formation in potato (Solanum tuberosum) (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 75 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The hormonal regulation of the consecutive steps in the formation of tubers on the potato plant (Solanum tuberosum L.) is described and discussed. An integrated view of the complex regulation of the initiation and growth of stolons and tubers is presented, with special emphasis on the commonly observed lack of synchronization of the various steps in tuber formation within a plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb05619.x
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of pH, sucrose and potassium ions in the phloem sap of castor bean (Ricinus communis) plants (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 77 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The composition of phloem sap, sampled at different heights along, the stem of castor bean (Ricinus communis L. cv. Gibsonii) plants, was determined. A gradient in pH was observed; the highest pH values occurred near the shoot apex, decreasing towards the base of the stem. The sucrose content of the exudate exhibited a similar gradient. The concentration of potassium ions was highest near the uppermost, full-grown leaves, decreasing towards the apex and the base of the stem. The importance of these findings for the understanding of phloem translocation and unloading is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb05657.x
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  • 8
    Electronic Resource
    Electronic Resource
    The genetics of plant metabolism (2006)
    [s.l.] : Nature Publishing Group
    Nature genetics 38 (2006), S. 842-849 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Variation for metabolite composition and content is often observed in plants. However, it is poorly understood to what extent this variation has a genetic basis. Here, we describe the genetic analysis of natural variation in the metabolite composition in Arabidopsis thaliana. Instead of focusing on ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/ng1815
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of phloem exudation from castor-bean cotyledons (1988)
    Springer
    Planta 174 (1988), S. 380-384 
    Details
    ISSN: 1432-2048
    Keywords: Phloem loading ; Phloem sap composition ; Phloem transport ; Ricinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exudate was collected fromRicinus communis L. cotyledons after cutting the hypocotyl. It contained high levels of sucrose and potassium, a low level of calcium, and a pH of approx. 7.5. After application of [14C] sucrose to the cotyledons, radioactivity could be recovered from the exudate, indicating that the exudate was derived from the phloem. Using data from a number of individual seedlings, correlations between loading rates of sucrose, translocation rates, and sucrose and potassium contents were analyzed. A positive correlation was found between the rate of sucrose loading and the rate of sucrose exudation, whereas a negative correlation existed between the contents of sucrose and potassium in the phloem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959524
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  • 10
    Electronic Resource
    Electronic Resource
    Developmental changes of enzymes involved in conversion of sucrose to hexose-phosphate during early tuberisation of potato (1997)
    Springer
    Planta 202 (1997), S. 220-226 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Fructokinase ; Hexokinase ; Invertase ; Solanum ; Sucrose synthase ; Tuberisation (sucrose metabolism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. A highly synchronised in-vitro tuberisation system, based on single-node cuttings containing an axillary bud, was used to investigate the activity patterns of enzymes involved in the conversion of sucrose to hexose-phosphates during stolon-to-tuber transition of potato (Solanum tuberosum L.). Two different non-tuberising systems were included to distinguish between changes that are or are not tuber-specific. At tuberisation the activity of soluble acid invertase decreased (13-fold) and of sucrose synthase increased (12-fold). The activity of both enzymes remained unchanged in the non-tuberising treatments. Based on the opposite patterns and large difference in activity of these two sucrolytic enzymes, we conclude that sucrose synthase constitutes the predominant route of sucrose breakdown after tuber initiation. During the period before tuberisation, the activity of cell-wall-bound invertase and of hexokinase showed a highly positive correlation (r 2 = 0.96 in all the three treatments, suggesting coordinated coarse control of both enzyme activities. After the onset of tuberisation cell-wall-bound invertase activity decreased to a very low level, a change not observed in the non-tuberising systems, indicating that cell-wall-bound invertase is presumably not involved in the unloading mechanism and/or short-distance transport of sucrose within the perimedulla of growing tubers. The overall activity of fructokinase and of hexokinase both showed a fourfold increase after tuber initiation, but remained unchanged in the non-tuberising systems. The increase of fructokinase suggests that the phosphorylation of fructose by fructokinase down-regulates the cytosolic fructose content in order to maintain a high sucrose-synthase-catalysed net flux of sucrose to phosphorylated hexoses during rapid tuber growth. The increase of total glucose-phosphorylating potential could be a response to the tuberisation-related starch accumulation process. The activity of UDP-glucose pyrophosphorylase showed no developmental change. The level of UDP-glucose pyrophosphorylase activity is very likely the result of metabolic regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050122
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