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  • 1
    ISSN: 1432-1939
    Keywords: Carbon isotope ratio ; Gas exchange ; Metrosideros ; Nitrogen-use efficiency ; Water-use efficiency ; Bog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Carbon isotope composition, photosynthetic gas exchange, and nitrogen content were measured in leaves of three varieties of Metrosideros polymorpha growing in sites presenting a variety of precipitation, temperature and edaphic regimes. The eight populations studied could be divided into two groups on the basis of their mean foliar δ13C values, one group consisting of three populations with mean δ13C values ca.-26‰ and another group with δ13C values ca.-28‰. Less negative δ13C values appeared to be associated with reduced physiological availability of soil moisture resulting from hypoxic conditions at a poorly drained high elevation bog site and from low precipitation at a welldrained, low elevation leeward site. Gas exchange measurements indicated that foliar δ13C and intrinsic wateruse efficiency were positively correlated. Maximum photosynthetic rates were nearly constant while maximum stomatal conductance varied substantially in individuals with foliar δ13C ranging from-29 to-24‰. In contrast with the patterns of δ13C observed, leaf nitrogen content appeared to be genetically determined and independent of site characteristics. Photosynthetic nitrogenuse efficiency was nearly constant over the range of δ13C observed, suggesting that a compromise between intrinsic water- and N-use efficiency did not occur. In one population variations in foliar δ13C and gas exchange with leaf cohort age, caused the ratio of intercellular to atmospheric partial pressure of CO2 predicted from gas exchange and that calculated from δ13C to be in close agreement only in the two youngest cohorts of fully expanded leaves. The results indicated that with suitable precautions concerning measurement protocol, foliar δ13C and gas exchange measurements were reliable indicators of potential resource use efficiency by M. polymorpha along environmental gradients.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Mistletoes ; Mangrove trees ; Gas exchange ; Water relations ; Carbon isotope ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gas exchange and water relations of the hemiparasite Pthirusa maritima and two its mangrove host species, Conocarpus erectus and Coccoloba uvifera, were studied in an intertidal zone of the Venezuelan coast. Carbon uptake and transpiration, leaf osmotic and total water potential, as well as nutrient content in the xylem sap and leaves of mistletoes and hosts were followed through the dry and wet season. In addition, carbon isotope ratios of leaf tissue were measured to further evaluate water use efficiency. Under similar light and humidity conditions, mistletoes had higher transpiration rates, lower leaf water potentials, and lower water use efficiencies than their hosts. Potassium content was much higher in mistletoes than in host leaves, but mineral nutrient content in the xylem sap of mistletoes was relatively low. The resistance of the liquid pathway from the soil to the leaf surface of mistletoes was larger than the total liquid flow resistance of host plants. Differences in the daily cycles of osmotic potential of the xylem sap also indicate the existence of a high resistance pathway along the vascular connection between the parasite pathway along the vascular connection between the parasite and its host. P. maritima mistletoes adjust to the different physiological characteristics of the host species which it parasitizes, thus ensuring an adequate water and carbon balance.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 242 (1985), S. 17-23 
    ISSN: 1432-0878
    Keywords: Brain lesions ; 3H Thymidine incorporation ; Astrocytes ; Monocytes/Macrophages ; Capillaries ; Ischemia ; Mongolian gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Tritiated thymidine autoradiography was used to measure cellular proliferation after ischemic injury in gerbil brain. Gerbils were subjected to bilateral occlusion of the common carotid arteries which resulted in areas of necrosis, or infarcts, in the posterior thalamus or midbrain. From 12 h to 10 days following the ischemia, gerbils were injected with 3H thymidine, sacrificed 4 h later, and the brains sectioned. In order to identify astrocytes and monocytes/macrophages, immunocytochemistry was performed prior to autoradiography, using antisera against glial fibrillary acidic protein and endothelial-monocyte reticuloendothelial antigen, respectively. Immunocytochemistry was also used to visualize microvessel laminin, myelin, and leakage of serum albumin. Lastly, a histochemical procedure for acid phosphatase activity was employed to verify cellular phagocytic activity in the wound. A reproducible sequence of reactions took place during the first 10 days after ischemia. Early changes included leakage of albumin and myelin breakdown, followed by arrival of monocytes at 2 days and their differentiation into macrophages by 5 days. These cells exhibited intense proliferation from 2 to 6 days post-ischemia. Microvessel endothelial cells were maximally labeled at 4 days post-ischemia. Hypertrophied astrocytes were apparent at 2 days and proliferated from 3 to 7 days post-ischemia, and by 10 days the wound was replaced by a “glial scar”.
    Type of Medium: Electronic Resource
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