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1

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Comparative measurements of chlorophyll a fluorescence, acid accumulation and gas exchange in exposed and shaded plants of Clusia minor L. and Clusia multiflora H. B. K. in the field (1997)

Grams, T. E. E. ; Haag-Kerwer, A. ; Olivares, Elizabeth ; [et al.]

Springer

Trees 11 (1997), S. 240-247

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ISSN: 0931-1890

Keywords: Key words Chlorophyll a fluorescence ; Clusia ; Crassulacean acid metabolism (CAM) ; Electron transport rate through photosystem II ; Malate decarboxylation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Changes in chlorophyll a fluorescence during the day and diurnal-changes of net CO2-exchange and organic acid contents were determined in two species of the genus Clusia during the dry season in Venezuela. The investigations included plants of the C3/CAM intermediate species Clusia minor and the C3 species C. multiflora growing at exposed and shaded sites. Both species showed a C3 pattern of net CO2-exchange at the exposed site. In the shade under extreme drought stress C. minor showed a weak expression of CAM without CO2-uptake during the afternoon (phase IV of CAM). C. multiflora growing in the shade exhibited a C3-pattern of net CO2-exchange and a small but significant nocturnal accumulation of citrate. Shaded plants of C. minor were able to double their light utilisation for electron transport and to reduce non-photochemical quenching during phase III compared to phase II of CAM. Furthermore, increase of electron transport rate through photosystem II in phase III of CAM is correlated to decarboxylation of malate. At the exposed site C. multiflora was less negatively affected by high PPFD than C. minor. This was shown by a lower reduction of potential electron quantum yield (Fv/Fm) and higher light utilisation of electron transport of C. multiflora compared to C. minor. At the exposed site C. minor did not make use of the CAM option to increase light utilisation of electron transport and to reduce non-photochemical quenching as did the plants growing in the shade.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/PL00009670

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Phosphoenolpyruvate carboxylase in mistletoe leaves: Regulation of gene expression, protein content, and covalent modification (2001)

Li, Xuemei ; Wanek, Wolfgang ; Nehls, U. ; [et al.]

Copenhagen : Munksgaard International Publishers

Physiologia plantarum 112 (2001), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Seasonal changes in the activity of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31), a key enzyme in the interaction of carbohydrate and nitrogen metabolism, were studied in leaves of the C3 semiparasitic mistletoe, Viscum album, growing on different host trees. Maximum extractable PEPCase activities were higher in leaves of mistletoes growing on Betulapendula and Alnusglutinosa hosts compared with those on the conifers, Abies alba and Larix decidua. Independent of host, maximum extractable PEPCase activities were high in spring and autumn while low in summer. Samples with higher PEPCase activities showed higher amounts of PEPCase protein and higher PEPCase mRNA levels. A curvilinear correlation between leaf total nitrogen content and the maximum extractable PEPCase activity as well as PEPCase mRNA level suggested that nitrogen might affect the activity of PEPCase of mistletoe by up-regulating gene expression. In addition to extractable activity, seasonal changes of the PEPCase activation state, the ratio of activities resulting from limited:non-limited assays, were found, which was correlated to the variation of malate content in leaves of mistletoe. ATP-dependent activation of PEPCase was characterized by an increase in I0.5(l-malate), indicating that PEPCase of leaves of mistletoes is probably regulated via phosphorylation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1120307.x

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3

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Responses of communities of tropical tree species to elevated CO2 in a forest clearing (1998)

Lovelock, Catherine E. ; Winter, Klaus ; Mersits, Roman ; [et al.]

Springer

Oecologia 116 (1998), S. 207-218

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ISSN: 1432-1939

Keywords: Key words Elevated CO2 ; Biomass allocation ; Successional status ; Leaf chemistry ; Tropical forest tree species

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Communities of ten species of tropical forest tree seedlings from three successional classes were grown at ambient and elevated CO2 in large open-top chambers on the edge of a forest in Panamá. Communities grew from 20 cm to approximately 2 m in height in 6 months. No enhancements in plant biomass accumulation occurred under elevated CO2 either in the whole communities or in growth of individual species. Reductions in leaf area index under elevated CO2 were observed, as were decreases in leaf nitrogen concentrations and increases in the C:N ratio of leaf tissue. Species tended to respond individualistically to elevated CO2, but some generalizations of how successional groupings responded could be made. Early and mid-successional species generally showed greater responses to elevated CO2 than late-successional species, particularly with respect to increases in photosynthetic rates and leaf starch concentrations, and reductions in leaf area ratio. Late-successional species showed greater increases in C:N ratios in response to elevated CO2 than did other species. Our results indicate that there may not be an increase in the growth of regenerating tropical forest under elevated CO2, but that there could be changes in soil nutrient availability because of reductions in leaf tissue quality, particularly in late-successional species.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004420050581

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4

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Chemical composition of halophytes from the Neusiedler Lake region in Austria (1977)

Albert, R. ; Popp, Marianne

Springer

Oecologia 27 (1977), S. 157-170

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The ionic relations in halophytes from the region east of Neusiedler Lake in Austria have been investigated. The study encompasses the following compounds: Na, K, Mg, Ca; Cl, SO4, phosphate, nitrate, and organic acids. The ionic composition varies substantially among the species investigated. Frequently a specific pattern of ion content can be found within a specific taxon. a) Dicotyledons: Extraordinary accumulation of sodium, high intake of inorganic ions (mainly Cl, less SO4), and regular occurrence of free oxalate, causing low Ca-concentrations, are typical for Chenopodiaceae and Caryophyllaceae (Spergularia media). Lepidium crassifolium shows similar sodium preponderance accompanied by high levels of SO4, Cl, and organic anions other than oxalate (mainly citrate and malate). The remaining dicotyledons show rather moderate salt content; Asteraceae and Cichoriaceae prefer Cl, and Plantago maritima accumulates high amounts of SO4 as well as Cl. Malate and citrate are, without exception, the main organic anions. The K:Na ratios in dicotyledons (esp. Chenopodiaceae and Lepidium-Brassicaceae) lie far below unity. b) Monocotyledons: In marked contrast, Poaceae, Cyperaceae, and Juncaceae are characterized by a general low salt status. With few exceptions, Cl is stored as the main inorganic anion, phosphate reaches higher levels than in dicotyledons and in many cases lies in nearly the same concentration range as SO4. The pattern of organic anions with malate and citrate as the main acids, does not basically differ from nonhalophilous species. In any case, K:Na ratio exceeds unity. Triglochin maritimum is the only monocotyle species exhibiting as high salt content and low K:Na ratios as dicotyledons. Nitrate and phosphate are of minor quantitative importance with regard to their osmotic efficiency; their mEq percentage of the total anion concentration range between 0.03 to 2.6 (NO3) and 0.5 to 13.6 (phosphate), respectively. The results are discussed from different points of view: on the one hand, the general problems of salt tolerance, on the other hand, the taxonomical and ecological aspects. beneficial to plant growth in view of salt sensitivity of enzymatic reactions. However, low osmotic potential of cell sap, and consequently, the acquisition of water is guaranteed by storing high amounts of sugars: according to our data (Albert and Popp, in preparation) total sugar concentration in halophilous Poaceae, Cyperaceae, and Juncaceae amounts to up to 200 mmol·l-1 fresh water, whereas in salt rich dicotyle species the sugar content is comparatively low (up to 50 mmol).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00345820

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5

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Effect of elevated CO2 on growth and crassulacean-acid-metabolism activity of Kalanchoë pinnata under tropical conditions (1997)

Winter, Klaus ; Richter, Andreas ; Engelbrecht, Bettina ; [et al.]

Springer

Planta 201 (1997), S. 389-396

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ISSN: 1432-2048

Keywords: Key words: Carbohydrate metabolism ; CO2 exchange ; Crassulacean acid metabolism (elevated CO2) ; Kalanchoë (elevated CO2) ; Organic acid metabolism

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. Kalanchoë pinnata (Lam.) Pers. (Crassulaceae), a succulent-leaved crassulacean-acid-metabolism plant, was grown in open-top chambers at ambient and elevated (two times ambient) CO2 concentrations under natural conditions at the Smithsonian Tropical Research Institute, Republic of Panama. Nocturnal increase in titratable acidity and nocturnal carbon gain were linearly related, increased with leaf age, and were unaffected by CO2 treatments. However, under elevated CO2, dry matter accumulation increased by 42–51%. Thus, the increased growth at elevated CO2 was attributable entirely to increased net CO2 uptake during daytime in the light. Malic acid was the major organic acid accumulated overnight. Nocturnal malate accumulation exceeded nocturnal citrate accumulation by six-to eightfold at both CO2 concentrations. Basal (predawn) starch levels were higher in leaves of plants grown at elevated CO2 but diurnal fluctuations of starch were of similar magnitude under both ambient and elevated CO2. In both treatments, nocturnal starch degradation accounted for between 78 and 89% of the nocturnal accumulation of malate and citrate. Glucose, fructose, and sucrose were not found to exhibit marked day-night fluctuations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250050081

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6

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Solutes and succulence in southern African mistletoes (1995)

Popp, Marianne ; Mensen, Ruth ; Richter, Andreas ; [et al.]

Springer

Trees 9 (1995), S. 303-310

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ISSN: 1432-2285

Keywords: Parasitic angiosperm ; Succulence ; Cations ; Organic osmolytes ; Cyclitols

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The inorganic ion and organic solute composition of Tapinanthus oleifolius (Loranthaceae) and Viscum rotundifolium (Viscaceae) growing on various host trees in Namibia were investigated. Organic osmolytes accounted for 22.8–45.1% of the total solutes determined in leaves of the mistletoes parasitizing Acacia nebrownii, Catophractes alexandri, Grewia flava and Ziziphus mucronata. On other hosts (Acacia karroo, Euphorbia virosa, Salvadora persica and Tamarix usneoides) T. oleifolius showed distinct succulence with increasing leaf age, with leaves more than 3 mm thick on E. virosa. In the more succulent leaves (〉 1.1 kg H2O m−2 leaf area) organic solutes were only of minor importance. Water content per leaf area was significantly correlated with chloride content per leaf area, suggesting that succulence served as a means to keep ion concentration at a physiological tolerable level. At whole plant levels 93.7% of the total sodium of the mistletoe bush was located in leaves thicker than 1 mm for T. oleifolius parasitizing Tamarix usneoides. This pronounced sequestration of sodium in older leaves as well as the high variability of the K/Na ratio in various parts of the parasite-host system point to highly selective ion distribution processes in this association.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00202493

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Effects of rhizospheric bicarbonate on net nitrate uptake and partitioning between the main nitrate utilising processes in Populus canescens and Sambucus nigra (2000)

Wanek, Wolfgang ; Popp, Marianne

Springer

Plant and soil 221 (2000), S. 13-24

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ISSN: 1573-5036

Keywords: assimilation ; dissolved inorganic carbon ; nitrate ; uptake ; xylem transport

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Increased levels of rhizospheric dissolved inorganic carbon have repeatedly been demonstrated to enhance plant growth by up to 80%, although carbon from dark fixation accounts for only 1–3% of total plant carbon gain. This study, therefore, aimed at investigating the effects of bicarbonate on nitrate uptake, assimilation and translocation to shoots. Clonal saplings of poplar (Populus canescens(Ait.) Sm.) and elder (Sambucus nigraL.) were grown hydroponically for 35 days in a nutrient solution containing 0, 0.5 and 1 mM bicarbonate and 2 mM nitrate as the sole nitrogen source at pH 7.0. Net nitrate uptake, root nitrate accumulation and reduction, and export of nitrogenous solutes to shoots were measured after incubating plants with 15N-labelled nitrate for 24 h. Net nitrate uptake increased non-significantly in plant species (19–61% compared to control plants) in response to 1 mM bicarbonate. Root nitrate reduction and nitrogen export to shoots increased by 80 and 95% and 15 and 44% in poplar and elder, respectively. With enhanced root zone bicarbonate, both species also exhibited a marked shift between the main nitrate utilising processes. Poplar plants increasingly utilised nitrate via nitrate reduction (73–88% of net nitrate uptake), whereas the proportions of export (20–9%) and storage in roots (7–3%) declined as plants were exposed to 1 mM external bicarbonate. On the other hand, elder plants exhibited a significant increase of root nitrate reduction (44–66%) and root nitrate accumulation (6–25%). Nitrate translocation to elder shoots decreased from 50 to 8% of net nitrate uptake. The improved supply of nitrogen to shoots did not translate into a significant stimulation of growth, relative growth rates increased by only 16% in poplar saplings and by 7% in elder plants.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004745823911

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