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1

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Abscisic-acid-induced turion formation in Spirodela polyrrhiza L. IV. Comparative ion flux characteristics of the turion and the vegetative frond and the effect of ABA during early turion development (1984)

SMART, CHERYL C. ; TREWAVAS, ANTHONY J.

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 7 (1984), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract Using the method of compartmental analysis, the ion fluxes and compartment concentrations of Ca2+, K+ and Cl- have been compared in the untreated vegetative frond and the abscisic acid (ABA) induced turion of Spirodela polyrrhiza. The ABA-induced turion is characterized by reduced Ca2+ exchange across the tonoplast and low vacuolar Ca2+ concentration relative to the vegetative frond. In addition the turion exhibits a higher plasmalemma flux with a correspondingly high Ca2+ concentration in the cytoplasm. The concentration of K+ and Cl- is much lower in the cytoplasm of the ABA-induced turion than in the vegetative frond with the influx/efflux ratio at both the plasmalemma and the tonoplast being less than 1, a finding exhibited also in dormant storage tissue.Treatment of vegetative fronds with ABA for 18 h resulted in a reduced K+ plasmalemma efflux relative to untreated vegetative fronds and a concomitant increase in the cytoplasmic concentration. There was no rapid effect of ABA on Ca2+, K+ or Cl- fluxes through either membrane. These results are consistent with the notion that drastic changes in ion fluxes and concentrations in the turion are a secondary consequence of ABA-induced development, possibly due to prior regulation by ABA of enzymes inherent to processes involved in membrane transport.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/1365-3040.ep11616215

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Abscisic-acid-induced turion formation in Spirodela polyrrhiza L. II. Ultrastructure of the turion; a stereological analysis (1983)

SMART, CHERYL C. ; TREWAVAS, ANTHONY J.

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 6 (1983), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract The ultrastructural features of the abscisic-acid-induced turion of Spirodela polyrrhiza are briefly described and a comparison between turion and vegetative frond tissue was made by stereological analysis. The turion is characterized by its small size, reniform shape, and dark-brown coloration; the mesophyll is undifferentiated and totally lacking the substantial acrenchyma development found in the vegetative frond. The turion cells have a smaller vacuole and a denser cytoplasm than the cells of the vegetative frond. Stereological analysis showed that the tissues differed quantitatively only in three main respects: air space formation, vacuolation, and starch and cell wall material accumulation. During development, it is suggested that the cells of the turion, while reaching the same final size as the vegetative frond cells, accumulate numerous starch grains, thick cell walls, and large deposits of tannins and anthocyanin pigment at the expense of the vacuolar expansion characteristic of the normal maturity programme. Certain features of the turion ultrastructure indicate a differential cell sensitivity to ABA.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/1365-3040.ep11588143

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Abscisic-acid-induced turion formation in Spirodela polyrrhiza L III. Specific changes in protein synthesis and translatable RNA during turion development (1984)

SMART, CHERYL C. ; TREWAVAS, ANTHONY J.

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 7 (1984), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract The developmental process leading to the formation of the abscisic acid (ABA) induced turion of Spirodela polyrrhiza was accompanied by a repression of nucleic acid and protein synthesis. DNA synthesis in the developing lurion (induced by 10−4mol m−3 ABA) was inhibited within 3h of ABA addition, followed by a repression of protein synthesis after 24 h, while RNA synthesis was not inhibited until 3 d. The inhibitory effect of ABA on protein synthesis was found to be selective and the synthesis of several novel proteins appeared to be induced. These effects were specific to ABA-sensitive tissue.The relationship between the changes in the protein and mRNA profiles during the development of the turion was investigated. The rapid general inhibition of protein synthesis at early stages of lurion formation could not be accounted for by the level of translatable mRNA, indicating an effect of ABA at the translational level. The specific alteration to the pattern of in vivo labelled proteins could have resulted, however, from control of the level of specific mRNAs for those particular proteins. Only after 3 d in ABA, when the developing primordium is committed to the turion developmental pathway, is there a total inhibition in the production of mRNA leading to the shutdown of all primary processes and the onset of the irreversible events leading to the dormant state.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3040.1984.tb01565.x

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4

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Abscisic-acid-induced turion formation in Spirodela polyrrhiza L. I. Production and development of the turion (1983)

SMART, CHERYL C. ; TREWAVAS, ANTHONY J.

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 6 (1983), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract The production, growth, and development of the abscisic-acid-induced turion (a small dormant bud) of Spirodela polyrrhiza were investigated. Addition of ABA to a culture of S. polyrrhiza resulted in growth inhibition at concentrations as low as 10−6molm−3, growth being completely arrested at 10−2 mol m. Over a single order of magnitude range around I0−4molm−3, ABA also induced the production of turions. The range of turion-producing concentrations of ABA was found to be much narrower than previously reported, turion production having a clearly defined threshold, optimum, and upper limit. The possibility that growth inhibition and turion formation are integrally linked aspects of a single response is discussed. Only primordia ≤0.7 mm long at the time of ABA addition could be induced to develop into turions and the events leading to turion formation were found to be reversible up to 72 h in ABA. It is concluded that in terms of turion formation there is a sensitivity window to abscisic acid lasting some 4–20h in the normal developmental life of frond cells. Providing cells experience the appropriate signal in this sensitivity window they initiate a new programme which eventually leads to turion formation. Microscopical analysis showed that the cells within this sensitivity window were still actively dividing. It is suggested that the developmental switch-over to rapid cell expansion and separation marks the end of this ABA sensitivity window.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/1365-3040.ep11588135

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5

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Abscisic acid-induced changes in inositol metabolism in Spirodela polyrrhiza (2000)

Flores, Susan ; Smart, Cheryl C.

Springer

Planta 211 (2000), S. 823-832

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ISSN: 1432-2048

Keywords: Key words: Abscisic acid – Inositol – Inositol trisphosphate synthase – Phytic acid –Spirodela– Turion

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. In response to abscisic acid (ABA), the duckweed Spirodela polyrrhiza (L.) activates a developmental pathway that culminates in the formation of dormant structures known as turions. Levels of the mRNA encoding d-myo-inositol-3-phosphate synthase (EC.5.5.1.4) which converts glucose-6-phosphate to inositol-3-phosphate, increase early in response to ABA. In order to understand the role of this enzyme in turion formation, we have investigated changes in inositol metabolism in ABA-treated plants. Here, we show that ABA-treatment leads to a 3-fold increase in free inositol, which peaks 2 d after treatment. This increase is followed by sequential increases in inositol phosphates and in accumulation of inositol hexakisphosphate (InsP6), in particular. In addition, we observed an early increase in a novel inositol bisphosphate which is not directly on the pathway to InsP6. In control plants, we observed synthesis and turnover of both inositol pentakisphosphate and InsP6. Two compounds more polar than InsP6 (diphosphoinositol polyphosphates) were present in both ABA-treated and control plants. Together, this suggests that the role of InsP6 in plants may be more complex than simply that of a storage compound during dormancy.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250000348

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6

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Overexpression of D-myo-inositol-3-phosphate synthase leads to elevated levels of inositol in Arabidopsis (1997)

Smart*, Cheryl C. ; Flores, Susan

Springer

Plant molecular biology 33 (1997), S. 811-820

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ISSN: 1573-5028

Keywords: Spirodela polyrrhiza/ ; D-myo-inositol-3-phosphate synthase ; inositol ; overproduction ; Arabidopsis thaliana/ ; salt stress

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract In this paper, we report on the generation of transgenic Arabidopsis plants containing elevated levels of the gene product encoding the enzyme catalysing the first committed step in inositol biosynthesis, D-myo-inositol-3-phosphate (Ins3P) synthase. These plants exhibit both an increase in Ins3P synthase activity and an increase in the level of free inositol of over four-fold compared to wild-type plants. Despite these changes, we could detect no significant difference in phenotype in the transgenic plants for a number of characteristics linked with putative functions of inositol and inositol-derived metabolites. Our results indicate that the proposed engineering of inositol metabolism to generate specific plant phenotypes (e.g. salt tolerance) may require the manipulation of several genes, and that Ins3P synthase activity can be manipulated to increase the pool size of free inositol.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005754425440

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7

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The influence of lignification on the development of vascular tissue inVigna radiata L. (1985)

Smart, Cheryl C. ; Amrhein, N.

Springer

Protoplasma 124 (1985), S. 87-95

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ISSN: 1615-6102

Keywords: L-α-aminooxy-β-phenylpropionic acid ; Lignification ; Secondary cell wall ; Ultrastructure ; Vigna radiata ; Xylem

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary During the early development of mungbean seedlings, treatment with L-α-aminooxy-β-phenylpropionic acid (AOPP), a potent specific inhibitor of phenylalanine ammonia-lyase, results in an inhibition of anthocyanin and lignin synthesis. The xylem vessels of the hypocotyl and root of AOPP treated seedlings collapse, and the cellulose microfibrils of the unlignified secondary wall are separated from one another and lie disorganized in the lumen of the mature xylem cell. The differentiation of the secondary cell wall appears unaffected by AOPP treatment, as does the ultrastructure of the wall of the mature phloem fibers of the root which is also lignified in untreated tissue. The results are discussed in the light of current thinking on the role and development of lignification in the xylem vessel.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01279727

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