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  • 11
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Leaves of Stephania japonica and Smilax australis were characterized in situ on the coast of north-eastern New South Wales, Australia, where they were growing naturally in three different light environments: deep shade, in the understory of an open Eucalyptus forest where they received frequent sunflecks of high intensity, and in an exposed site receiving full sunlight. In deep shade the xanthophyll cycle remained epoxidized during the day and the vast majority of absorbed light was utilized for photosynthesis. In the exposed site both deepoxidation and epoxidation of the xanthophyll cycle and changes in the level of xanthophyll-dependent thermal energy dissipation largely tracked the diurnal changes in photon flux density (PFD). In the understory the xanthophyll cycle became largely deepoxidized to zeaxanthin and antheraxanthin upon exposure of the leaves to the first high intensity sunfleck and this high level of deepoxidation was maintained throughout the day both during and between subsequent sunflecks. In contrast, thermal energy dissipation activity, and the efficiency of photosystem II, fluctuated rapidly in response to the changes in incident PFD. These findings suggest a fine level of control over the engagement of zeaxanthin and antheraxanthin in energy dissipation activity, presumably through rapid changes in thylakoid acidification, such that they became rapidly engaged for photoprotection during the sunflecks and rapidly disengaged upon return to low light when continued engagement might limit carbon gain.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical & experimental allergy 24 (1994), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. A follow-up study was carried out to determine whether either impaired or disproportionate fetal growth are associated with a raised total serum IgE concentration in men and women aged 50 years. The serum IgE concentration was measured in 146 men and 134 women born in Preston (Lancashire, UK) between 1935 and 1943, whose size at birth had been measured in detail.Sixty-two subjects were found to have an IgE concentration above 80 IU/ml. Compared with subjects with a normal IgE on average they had a 0.30 inch larger head circumference at birth (P -0.004) and weighed 5.6 ounces more at birth (P= 0.04). People with a raised and with a normal IgE were of similar crown-heel length at birth, indicating that in utero those with a raised IgE had had disproportionate growth of the head in relation to the trunk and limbs. The prevalence of a raised IgE rose from 14% in subjects whose head circumference at birth was 13 inches or less to 37% in those whose head circumference was more than 14 inches. This association was independent of gestational age at birth and of the mother's pelvic size and parity. It was also independent of adult physique, social class and smoking, and was similar in men and women. In multiple logistic regression analyses odds ratios of a raised IgE rose progressively to more than 4 as head circumference at birth increased from 13 inches or less to more than 14 inches.One possibility is that these associations reflect the long-term effects of sustaining fetal brain growth at the expense of the trunk, in particular the thymus. This may be a consequence of fetal under-nutrition in late gestation.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 376 (1995), S. 630-630 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - If one does not manipulate the numbers, the research output, impact and cost effectiveness in Australian universities continue to be dominated by the Institute of Advanced Studies (LAS) and the faculties of the Australian National University (ANU), not by the "sandstone club". For example, ...
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Plant Science Letters 32 (1983), S. 115-123 
    ISSN: 0304-4211
    Keywords: Excised wheat roots ; Ion uptake ; Malate decarboxylation ; Malate synthesis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The consequences of biotic stress have been poorly understood, partly because its application is difficult to control and partly because its physiological consequences are highly variable. Many plant viruses are recognised on the basis of leaf symptoms that depend on localised changes to chloroplast structure and function. This paper reviews recent progress in understanding early interactions between plant viruses and the photosynthetic apparatus, using chlorophyll fluorescence analysis of novel, defined algal-virus systems and using high resolution imaging of chlorophyll fluorescence and other photosynthetic processes in higher plant systems. We then consider the consequences of viral effects on photosynthetic functioning for whole plants and populations with an emphasis on the potential interactions with other environmental factors. Early responses indicated by increase in both non-photochemical quenching of fluorescence and increased reduction state of the primary electron transport acceptor QA suggest that, not surprisingly, both photoprotective and photoinhibitory processes contribute to the accelerated local demise of the photosynthetic apparatus and symptom development. In other cases, localised accumulations of carbohydrate and source-sink imbalance following infection may inhibit gene expression, leading to altered levels of chloroplast protein complexes and enzymes of photosynthetic metabolism coincident with symptom development. Recent experiments suggest that much of the variability in plant responses to biotic stress may result from interactions with other environmental factors, such as light intensity and nutrition. Experiments suggest that virus infections may have greater effects on fitness and competitive ability in low N, high light environments than in shaded, high nutrient conditions. Some ecological implications of these observations are discussed.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 58 (1971), S. 414-415 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-dependent 14CO2 fixation by the algae of Diplosoma virens (Hartmeyer) ranged between about 3 and 27 μmoles mg-1 chlorophyll h-1. The principal first products of 14C fixation were 3-phosphoglyceric acid and phosphorylated sugars, indicating that ribulose bisphosphate carboxylase was the primary carboxylation enzyme. The activity of this enzyme in crude extracts of the algae was 4 to 6 μmoles CO2 mg-1 chlorophyll h-1. The principal end product of 14C fixation by these algae in the ascidian host was a water-soluble oligosaccharide which was an α-1,4-glucan. A maximum of 7% of the 14C fixed was found in insoluble materials of the algae or its host after 60 min 14CO2 fixation. Whether the α-1,4-glucan is a product of algal or animal metabolism remains to be determined.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary At constant cladode temperature the stomatal resistance of O. inermis increased when the cladode-air vapor pressure difference was increased and stomatal resistance decreased when the cladode-air vapor pressure difference was lowered. Net CO2 fixation in the dark was very responsive to these humidity dependent changes in stomatal resistance. Net CO2 fixation and stomatal resistance in the light did not respond to changes in cladode-air vapor pressure differences in the light under the conditions tested. When temperature response functions for dark CO2 fixation were examined at constant ambient humidity, the reduction in dark CO2 fixation at higher temperatures was largely due to stomatal closure in response to the increased vapor pressure difference. The water requirement for net CO2 fixation in the dark at typical nocturnal vapor pressure differences was about 10 times lower than that of net CO2 fixation in the light at vapor pressure differences typical of the late afternoon. The role of the stomatal responses to humidity in determining the patterns and rates of net CO2 exchange in the light or dark, and its possible ecological significance is discussed.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 57 (1983), S. 316-321 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When grown with adequate water and nitrogen (12 mM NO 3 - ) four clones of Solanum dulcamara from sun or shade habitats in Europe showed similar potential for acclimation of photosynthesis to irradiance level during growth. When grown with limiting nitrogen (0.6 mM NO 3 - ) all clones showed a low potential for acclimation of photosynthesis to irradiance during growth. If limiting nitrogen was accompanied by water stress at high irradiance, the initial slope of the irradiance response curve, and the irradiance saturated rate of photosynthesis were depressed, especially in a clone from a shaded habitat. These interactions are discussed in terms of earlier reports on the sunshade responses and sun-shade ecotypic differentiation in this species.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 314 (1985), S. 200-200 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] KEELEY ET AL. REPLY-We agree with Cockburn that, although the presence of CAM in astomatous Stylites does not support his theory on the stomatal origin of CAM, it does not necessarily falsify the theory either. We also agree with Thomas that Stylites most reasonably should be included with ...
    Type of Medium: Electronic Resource
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