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  • 1
    Electronic Resource
    Electronic Resource
    Marcescence and senescence in a submediterranean oak (Quercus subpyrenaica E.H. del Villar): photosynthetic characteristics and nutrient composition (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have studied some characteristics of marcescent leaves (withered retained leaves) and senescent leaves in Quercus subpyrenaica, a tree species that plays a major role in the climatic transition forests between temperate and mediterranean environments in north-eastern Spain. Leaves were taken from the upper and lower halves of the tree crown, both in the south- and north-exposed parts of the tree. Leaves receiving low photosynthetic photon flux density (PPFD) undergo autumnal senescence, which is associated with decreases in photosynthetic pigments and decreases in the chlorophyll a to chlorophyll b ratio. Leaves receiving higher PPFD underwent senescence at a later date. Leaves situated in the upper, south-exposed part of the tree, which receive the highest PPFD, showed no signs of senescence and remained photosynthetically active for a longer period of time, marcescence occurring suddenly at the end of the season. Marcescence is unlikely to cause an improvement in nutrient recycling, since the removal of nutrients proceeded similarly in marcescent and senescent leaves. Marcescence may increase the time-span of the assimilation capacity for a significant period of time during September and October, when high light intensities and mild temperatures occur. The phenomena triggering marcescence may be related to low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00403.x
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  • 2
    Electronic Resource
    Electronic Resource
    Iron deficiency-induced changes in the photosynthetic pigment composition of field-grown pear (Pyrus communis L) leaves (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this work we characterize the changes induced by iron deficiency in the pigment composition of pear (Pyrus communis L.) leaves grown under high light intensities in field conditions in Spain. Iron deficiency induced decreases in neoxanthin and β-carotene concomitantly with decreases in chlorophyll a, whereas lutein and carotenoids within the xanthophyll cycle were less affected. Iron deficiency caused major increases in the lutein/chlorophyll a and xanthophyll cycle pigments/chlorophyll a molar ratios. The chlorophyll a/chlorophyll b ratio increased in response to iron deficiency. The carotenoids within the xanthophyll cycle in iron-deficient and in iron-sufficient (control) leaves underwent epoxidations and de-epoxidations in response to ambient light conditions. In control leaves dark-adapted for several hours, most of the xanthophyll cycle pigment pool was in the epoxidated form vio-laxanthin, whereas iron-deficient leaves had significant amounts of zeaxanthin. Iron-deficient leaves also exhibited an increased non-photochemical quenching, supporting the possibility of a role for pigments within the xanthophyll cycle in photoprotection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb02013.x
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  • 3
    Electronic Resource
    Electronic Resource
    Income distribution and composition of consumer demand in the Spanish economy
    Amsterdam : Elsevier
    European Economic Review 29 (1985), S. 1-13 
    Details
    ISSN: 0014-2921
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0014-2921(85)90035-2
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  • 4
    Electronic Resource
    Electronic Resource
    Inflation, relative prices and welfare redistribution in Spain, 1976-1984
    Amsterdam : Elsevier
    Economics Letters 20 (1986), S. 387-390 
    Details
    ISSN: 0165-1765
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0165-1765(86)90019-4
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  • 5
    Electronic Resource
    Electronic Resource
    An index of prices and taxes - Spain 1981-1987
    Amsterdam : Elsevier
    Economics Letters 28 (1988), S. 243-246 
    Details
    ISSN: 0165-1765
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0165-1765(88)90123-1
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  • 6
    Electronic Resource
    Electronic Resource
    Differences in the response of carbon assimilation to summer stress (water deficits, high light and temperature) in four Mediterranean tree species (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 102 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Daily changes in photoprotective mechanisms were studied in sun leaves of Quercus suber L., Quercus ilex L., Olea europaea L. and Eucalyptus globulus Labill. trees during the summer in Portugal. Even though stomatal closure explained most of the diurnal variation in carbon assimilation along the summer, a decline in the photochemical yield of photosystem II (F′v/F′m) also occurred, as a result of an excess of intercepted solar radiation when carbon assimilation is limited by stomatal closure due to high vapour pressure deficits and/or soil water deficits. These changes were accompanied by the conversion of violaxanthin to antheraxanthin and zeaxanthin which were correlated with thermal dissipation of excess photon energy. In spite of a common general response, differences between species were observed -Olea europaea, which is a slow-growing tree, had the lowest net photosynthetic rates, the highest proportion of carotenoids in relation to chlorophyll and the highest rates of de-epoxidation of violaxanthin. This enabled a large thermal dissipation of the excess intercepted radiation but led to rather small values of light utilisation for photochemistry (ca 20%). In contrast, in E. globulus, a fast-growing tree, photosynthetic rates were the highest, thermal dissipation of absorbed radiation the lowest and maximal values of light utilisation for photochemistry reached ca 50%. The two Quercus species exhibited an intermediate response. A high degree of co-ordination is apparent between stomatal behaviour, photosynthetic capacity and photoprotection mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1020310.x
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  • 7
    Electronic Resource
    Electronic Resource
    Iron-deficiency in pea leaves: Effect on lipid composition and synthesis (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 72 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The lipid composition of chlorotic leaves of Pisum sativum L. cv. Kelvedon Wonder, developed under iron-deficiency was determined and compared to similar material developed under normal nutrient conditions. All lipid classes were affected by iron-deficiency but to different extents, and thylakoid lipids were more affected than non-thylakoid lipids. The most striking results concerned changes in the fatty acid content of the main polar lipids. The linolenic acid of the galactolipids decreased to the benefit of more saturated fatty acids, mainly linoleic acid. In phosphatidylglycerol, the proportion of Δ3-trans-hexadecenoic acid decreased. Using radioactive acetate, lipid synthesis was investigated. Desaturation leading to linoleic acid was less affected by iron-deficiency than desaturation leading to Δ3-trans-hexadecenoic and linolenic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb06370.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of Salinity on Chlorophyll Fluorescence and Photosynthesis of Barley (Hordeum Vulgare L.) Grown Under a Triple-Line-Source Sprinkler System in the Field (1999)
    Springer
    Photosynthetica 36 (1999), S. 375-387 
    Details
    ISSN: 1573-9058
    Keywords: chlorophyll fluorescence ; cultivar differences ; photosystem 2 efficiency ; stomatal conductance and frequency ; transpiration rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In flag leaves of four cultivars of barley (Hordeum vulgare L.) grown in the field under a triple-line-source sprinkler system, that produces a linear soil salinity gradient, a decrease in net carbon dioxide assimilation rate (PN) and stomatal conductance for water vapour (gs) was found. These changes were related to salinity tolerance at moderate salinity. With increasing salinity, PN was saturated at low irradiances and stomatal frequencies increased. A decrease in photosystem 2 (PS2) efficiency was not found in the field after dark adaptation even at high salinity. Salinity induced only small decreases in the actual PS2 efficiency at midday steady-state photosynthesis, indicating that the photosynthetic electron transport was little affected by salinity. Therefore, using PS2 efficiency estimates in attached leaves is probably not a useful tool to screen barley genotypes grown under saline conditions in the field for salinity tolerance. In contrast, excised flag leaves from high salinity plots, once in the laboratory, exhibited a decrease in the variable to maximum chlorophyll fluorescence ratio as compared to excised leaves from control plants. On the other hand, the PN rate might allow for a good discrimination between tolerant and non-tolerant cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007019918225
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in sugar beet leaf plasma membrane Fe(III)-chelate reductase activities mediated by Fe-deficiency, assay buffer composition, anaerobiosis and the presence of flavins (1998)
    Springer
    Protoplasma 205 (1998), S. 163-168 
    Details
    ISSN: 1615-6102
    Keywords: Leaf plasma membrane ; Iron deficiency ; Ferric chelate reductase ; Flavin ; Apoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different assay conditions induce changes in the ferric chelate reductase activities of leaf plasma membrane preparations from Fe-deficient and Fe-sufficient sugar beet. With an apoplasttype assay medium the ferric chelate reductase activities did not change significantly when Fe(III)-EDTA was the substrate. However, with ferric citrate as substrate, the effect depended on the citrateto-Fe ratio. When the citrate-to-Fe ratio was 20 ∶ 1, the effects were practically unappreciable. However, with a lower citrate-to-Fe ratio of 5 ∶ 1 the activities were significantly lower with the apoplast-type medium than with the standard assay medium. Our data also indicate that anaerobiosis during the assay facilitates the reduction of ferric malate and Fe(III)-EDTA by plasma membrane preparations. Anaerobiosis increased by approximately 50% the plasma membrane ferric chelate reductase activities when Fe(III)-EDTA was the substrate. With ferric malate anaerobiosis increased activities by 70–90% over the values obtained in aerobic conditions. However, with ferric citrate the increase in activity by anaerobiosis was not significant. We have also tested the effect of riboflavin, flavin adenine dinucleotide, and flavin mononucleotide on the plasma membrane ferric chelate reductase activities. The presence of flavins generally increased activities in plasma membrane preparations from control and Fe-deficient plants. Increases in activity were generally moderate (lower than twofold). These increases occurred with Fe(III)-EDTA and Fe(III)-citrate as substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279306
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  • 10
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    Effects of cadmium on cork oak (Quercus suber L.) plants grown in hydroponics (2011)
    Oxford University Press
    Details
    Publication Date: 2011-12-13
    Description: Cork oak ( Quercus suber L.) is an autochthonous tree species that is being used for reforestation in heavy-metal-contaminated areas in Spain. A hydroponics experiment was carried out to characterize the effects of Cd on several morphological and physiological parameters in this species, including shoot length, nutrient concentrations and allocation in different organs, leaf pigment concentrations, photosynthetic efficiency, root ferric chelate reductase (FCR) activity and organic acid concentrations in xylem sap. Four different Cd treatments were applied, adding Cd chelated with EDTA or as chloride salt at two different concentrations (10 and 50 µM Cd). After 1 month of Cd treatment, plant growth was significantly inhibited in all treatments. Results indicate that Cd accumulates in all organs 7- to 500-fold when compared with control plants. The highest Cd concentration was found in the 50 µM CdCl 2 treatment, which led to concentrations of ~30, 123 and 1153 µg Cd g –1 dry weight in leaves, stems and roots, respectively. In the strongest Cd treatments the concentrations of P and Ca decreased in some plant parts, whereas the Mn leaf concentrations decreased with three of the four Cd treatments applied. The concentrations of chlorophyll and carotenoids on an area basis decreased, whereas the (zeaxanthin plus antheraxanthin)/(total violaxanthin cycle carotenoids) ratio and the non-photochemical quenching increased significantly in all Cd treatments. Cadmium treatments caused significant increases in the activity of the enzyme FCR in roots and in the concentrations of organic acids in xylem sap. Some of the physiological changes found support the fact that Cd induces a deficiency of Fe in cork oak, although the plant Fe concentrations were not reduced significantly. At higher concentrations the effects of Cd were more pronounced, and were more marked when Cd was in the free ion form than when present in the form of Cd-EDTA.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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