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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 24 (2001), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relationship between drought, oxidative stress and leaf senescence was evaluated in field-grown sage (Salvia officinalis L.), a drought-susceptible species that shows symptoms of senescence when exposed to stress. Despite the photoprotection conferred by the xanthophyll cycle, drought-stressed senescing leaves showed enhanced lipid peroxidation, chlorophyll loss, reduced photosynthetic activity and strong reductions of membrane-bound chloroplastic antioxidant defences (i.e. β-carotene and α-tocopherol), which is indicative of oxidative stress in chloroplasts. H2O2 accumulated in drought-stressed senescing leaves. Subcellular localization studies showed that H2O2 accumulated first in xylem vessels and the cell wall and later in the plasma membrane of mesophyll cells, but not in chloroplasts, indicating reactive oxygen species other than H2O2 as direct responsible for the oxidative stress observed in the chloroplasts of drought-stressed senescing leaves. The strong degradation of β-carotene and α-tocopherol suggests an enhanced formation of singlet oxygen as the putative reactive oxygen species responsible for oxidative stress to senescing chloroplasts. This study demonstrates that oxidative stress in chloroplasts mediates drought-induced leaf senescence in sage growing in Mediterranean field conditions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography A 503 (1990), S. 459-465 
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 210 (2000), S. 263-267 
    ISSN: 1438-2385
    Keywords: Key words Rosmarinus officinalis ; Phenolic diterpenes ; Carnosic acid ; Carnosol ; 11,12-Di-O-methylisorosmanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The formation of phenolic diterpenes in the leaves of rosemary plants grown under Mediterranean climate was investigated. Low precipitation coincided with high solar radiation during the summer, resulting in water and light stress of the plants. The highest concentrations of the major diterpenes carnosic acid and carnosol were found during the winter and the lowest concentrations during the summer, which is likely to be the result of their enzymatic conversion in the presence of singlet oxygen. All other diterpenes followed different trends during the season. The concentration of carnosic acid increased with the relative water content of the leaf but decreased with increasing solar radiation and temperature. 11,12-di-O-Methylisorosmanol was found for the first time in rosemary leaves.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2048
    Keywords: Key words: Antioxidant – Chlorophyll – Diterpene – Drought –Rosmarinus (drought stress) – Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months and the chlorophyll content of leaves was reduced by up to 85% during the drought. In severe stress: (i) α-tocopherol increased 9-fold per g dry weight and 20-fold per unit of chlorophyll; (ii) lutein and β-carotene contents decreased on a dry-weight basis, but an 80% increase in lutein and constant levels of β-carotene were observed on a chlorophyll basis; (iii) there were transient and sustained increases in the de-epoxidation state of the xanthophyll cycle; and (iv) the highly oxidised abietane diterpene isorosmanol increased 8-fold as a result of the oxidation of carnosic acid. With the autumn rainfalls, water status, α-tocopherol and violaxanthin recovered first and the levels of photosynthetic pigments and abietane diterpenes increased later. The photoprotection conferred by the xanthophyll cycle and the antioxidant function of tocopherols, lutein and diterpenes may help to avoid irreversible damage in severe drought, making possible the recovery of functional membranes after the autumn rainfalls. Besides, chlorophyll loss reduces the amount of photons absorbed by leaves, which enhances the photoprotective and antioxidant capacity of leaves per amount of photons absorbed, since the ratios of xanthophylls, α-tocopherol and abietane diterpenes to chlorophyll increase.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5036
    Keywords: bermudagrass (Cynodon dactylon (L.) Pers.) ; nutrient content ; osmotic potential ; plant production ; seasonal changes ; water deficits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seasonal changes in water relations, production and mineral composition were studied in a sward ofCynodon dactylon (L). Pers. subjected to water deficits during a dry summer, and at recovery in autumn. The experiment was carried out under Mediterranean field conditions. Water deficits during summer reduced total dry matter production by 60%, but in autumn there were no differences between treatments. Compared to well-watered sward, the sward grown under drought showed an increase in potassium, calcium and nitrogen of 55, 10 and 10% respectively. These differences decreased with the arrival of autumn rains. Leaf osmotic potential (ΨΠ) fell during the dry summer to −2.8 MPa in well-watered plants and to −4.2 MPa in stressed plants. In autumn there were no differences between treatments. Nevertheless, relative water content (RWC) only decreased to 0.86 in droughted plants. In summer potassium contributed to the osmotic adjustment. In contrast, under water deficits a decrease of 71% in sodium and, to a lesser but significant extent decreases in phosphorus, magnesium and chlorine was observed. Nitrogen, phosphorus and sulphur showed low concentrations during summer and increased in autumn.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5087
    Keywords: Lavandula stoechas ; Rosmarinus officinalis ; ABA ; IAA ; ZR ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Water stress induced an increase in endogenous concentrations of ABA in Lavandula stoechas L. plants to 13100 pmol ABA g−1 FW, which may contribute to the maintenance of water relations between the second and the third day of water stress treatment. After the third day, a sharp decrease in ABA levels was observed to 2630 pmol ABA g−1 FW, together with a decrease in water content and water potential and a loss of plant response to water stress. Water deficit did not induce an increase in endogenous ABA concentration, which remained at 514 pmol ABA g−1 FW in Rosmarinus officinalis L., which is more sclerophyllous than L. stoechas. Nevertheless, the relative water content of Rosmarinus officinalis L. after seven days of water stress decreased more than 40% and ψ reached values of −3.2 MPa. R. officinalis showed lower levels of ABA, but significantly higher levels of IAA and ZR than L. stoechas (4 times and 6 times respectively in well watered-plants). The increase in ABA levels is not a common mechanism in these two Mediterranean shrubs which survive under water stress conditions.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5087
    Keywords: endogenous abscisic acid ; Fatsia japonica ; indole-3-acetic acid ; leaf water potential ; ultrastructure ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ultrastructural alterations in mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in water-stressed field-grown plants of Fatsia japonica. Under water deficit cellular membranes were modified and an increase in vesicles was observed. The main damage to the chloroplasts included thylakoid swelling and disruption of the chloroplast envelope. Concomitant variations in abscisic acid and indole-3-acetic acid were observed. Despite the expected increased in endogenous ABA concentration in relation to water stress, after the highest concentration of ABA, observed at predawn in severely stressed plants (29-1), there was a sharp decline from 2768 pmol g fw−1 to 145 pmol g fw−1; thus in severely stressed plants ABA levels were not related to changes in bulk leaf ABA contents. Water stress did not influence the concentrations of indole-3-acetic acid, although the increase in the endogenous abscisic acid concentration could be related with the ultrastructural changes.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5087
    Keywords: cell ultrastructure ; endogenous abscisic acid ; Fatsia japonica ; indole-3-acetic acid ; leaf water potential ; PEG ; selective staining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ultrastructural alterations in epidermal and mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in PEG-treated plants of Fatsia japonica Decne & Plank. Under stress induced by PEG vesicles containing fibrous material and electron-dense bodies associated with plasma membranes were observed. Cytochemical examination indicated that electron-dense bodies corresponded to lipids and the fibrous material of the vesicles were polysaccharides. Chloroplasts, mitochondria, nuclei and Golgi apparatus also showed modifications. A strong relationship was found between increasing PEG-induced water stress, increasing endogenous ABA and ultrastructural changes. In relation with leaf ontogeny and ABA concentration a higher ABA level was observed in younger than in older leaves. The differences in the endogenous concentrations of indole-3-acetic acid are unclear, except after 7 days of PEG-treatment. The increase in the endogenous abscisic acid concentration could be related with the ultrastructural changes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 16 (1995), S. 287-292 
    ISSN: 1573-5087
    Keywords: abscisic acid ; chloroplast ultrastructure ; immunolocalization ; Lavandula stoechas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A monoclonal antibody was used to localize abscisic acid in Lavandula stoechas L. plants treated with 1 μM abscisic acid. ABA localization was performed using EDC as the only fixative, which preserves antigenicity and improves the specificity of monoclonal antibodies. A relationship was observed between the effect of abscisic acid on chloroplast ultrastructure and ABA accumulation. Gold particles accumulated on swollen chloroplasts. Our findings provide cytochemical evidence that the chloroplast is a trapping compartment, and yield valuable information on the relation between chloroplast ultrastructure and ABA accumulation.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Photosynthetica 34 (1997), S. 67-76 
    ISSN: 1573-9058
    Keywords: Hordeum vulgare ; net photosynthetic rate ; osmotic adjustment ; osmotic potential ; relative water content ; stomatal conductance ; water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of water stress on plant water status and net photosynthetic gas exchange (PN) in six barley genotypes (Hordeum vulgare L.) differing in productivity and drought tolerance was studied in a controlled growth chamber. Osmotic adjustment (OA), PN, stomatal conductance (gs), and the ratio intercellular/ambient. CO2 concentration (Ci/Ca) were evaluated at four different levels of soil water availability, corresponding to 75, 35, 25 and 15 % of total available water. Variability in OA capacity was observed between genotypes: the drought tolerant genotypes Albacete and Alpha showed higher OA than drought susceptible genotypes Express and Mogador. The genotype Albacete exhibited also higher PN than the others at low water potential (Ψ). The ratios of PN/gs and Ci/Ca showed that differences in photosynthetic inhibition between genotypes at low Ψ were probably due to nonstomatal effects. In Tichedrett, a landrace genotype with a very extensive root development, OA was not observed, however, it exhibited a capacity to maintain its photosynthetic activity under water stress.
    Type of Medium: Electronic Resource
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