The Physiological Basis for the Contrasting Distribution Patterns of Acer Saccharum and Thuja Occidentalis at Cliff Edges

1990 ◽  
Vol 78 (4) ◽  
pp. 1063 ◽  
Author(s):  
R. M. Bartlett ◽  
D. W. Larson
Keyword(s):  
Acer Saccharum ◽  
Distribution Patterns ◽  
Physiological Basis ◽  
Thuja Occidentalis

Mineral Cycling and Lichens: The Physiological Basis

1991 ◽  
Vol 23 (3) ◽  
pp. 293-307 ◽  
Author(s):  
Dennis H. Brown ◽  
Rosalie M. Brown
Keyword(s):  
Toxic Metal ◽  
Distribution Patterns ◽  
Essential Elements ◽  
Mineral Matter ◽  
Physiological Basis ◽  
Wet And Dry Deposition ◽  
Mineral Cycling ◽  
Physiological Processes ◽  
Field And Laboratory Conditions

AbstractA number of physiological processes relevant to the role of lichens in mineral cycling are discussed. Consideration is given to the cellular location of positively-charged cations, showing (a) the benefits of quantifying intracellular elements for the interpretation of toxic metal stress, and (b) how distribution patterns of physiologically essential elements may be altered by desiccation and rehydration under field and laboratory conditions. The quantitative significance of these dynamic processes associated with metal uptake and loss requires verification under field conditions. A modified sequential elution procedure is proposed that enables quantification of insoluble paniculate mineral matter (acquired by wet and dry deposition) in addition to soluble elements in intercellular, extracellular-exchangeable and intracellular sites.

Mycorrhizal colonization and macronutrient status of cliff-edge Thuja occidentalis and Acer saccharum

Ecography ◽  
1992 ◽  
Vol 15 (3) ◽  
pp. 262-266 ◽  
Author(s):  
Uta Matthes-Sears ◽  
Christoph Neeser ◽  
Douglas W. Larson
Keyword(s):  
Acer Saccharum ◽  
Mycorrhizal Colonization ◽  
Thuja Occidentalis

Salinity tolerance in Spergularia marina

1985 ◽  
Vol 63 (10) ◽  
pp. 1762-1768 ◽  
Author(s):  
John M. Cheeseman ◽  
P. Bloebaum ◽  
Carol Enkoji ◽  
Linda K. Wickens
Keyword(s):  
Fresh Water ◽  
Higher Plants ◽  
Specific Effect ◽  
Distribution Patterns ◽  
Growth Stimulation ◽  
Solution Culture ◽  
Ion Content ◽  
Physiological Basis ◽  
Leaf Surface Area ◽  
Spergularia Marina

Attributes of the coastal halophyte Spergularia marina (L.) Griseb. that make it useful for studies of the physiological basis for salt tolerance in fully autotrophic higher plants are discussed. Growth, morphological, and ion-content characteristics are presented to serve as a background for subsequent studies of transport physiology. Plants were grown in solution culture on dilutions of artificial seawater or on the same solution without NaCl ("fresh water") from the time at which they could be conveniently transferred as seedlings (about 2 weeks old) to the onset of flowering about 5 weeks later. Eighteen days after transfer, plants growing on 0.2 × seawater were larger, being nearly twice the size of plants on fresh water. A Na+ specific effect was indicated, as the major part of the growth stimulation (54%) resulted from a 1 mM NaCl supplementation of "fresh water." Succulence was not a consideration in the growth response: root length was directly proportional to weight as was leaf surface area and neither was affected by salinity. Total Na+ plus K+ per gram root or shoot showed little variation with salinity from 1 to 180 mM Na+ levels. In roots, the relative Na+ and K+ contents were also little affected by salinity, but in the shoots, increasing salinity resulted in higher Na+ and lower K+ contents. Distribution within the shoots of 0.2 × plants showed no regions either free of or exceptionally high in Na+. The ion content and distribution patterns are compared with those in a number of other halophytes.

Environmental controls of carbon uptake in two woody species with contrasting distributions at the edge of cliffs

1990 ◽  
Vol 68 (11) ◽  
pp. 2371-2380 ◽  
Author(s):  
U. Matthes-Sears ◽  
D. W. Larson
Keyword(s):  
Water Potential ◽  
Acer Saccharum ◽  
Deciduous Forest ◽  
Light Limitation ◽  
Carbon Gain ◽  
Carbon Uptake ◽  
Severe Drought ◽  
Xylem Water Potential ◽  
Thuja Occidentalis ◽  
Environmental Controls

Thuja occidentalis L. and Acer saccharum Marsh, show mutually exclusive distribution patterns along forested cliff edges of the Niagara Escarpment; T. occidentalis occurs at the cliff edge and on the cliff face, whereas A. saccharum occurs with increasing frequency away from the cliff edge. To reveal the controls of such patterns, seasonal and diurnal courses of net photosynthesis (Pn), stomatal conductance (gs), and xylem water potential were measured in situ and related to fluctuations in light, temperature, and moisture. For each species, saplings growing in the cedar zone near the cliff edge were compared with saplings growing in the deciduous forest zone farther from the cliff edge on the plateau. The carbon uptake of both species was most often limited by light; limitation by temperature, atmospheric, or soil moisture was rare. Acer saccharum was slightly better adapted than T. occidentalis to growth at the low light levels in both zones because of a greater light-use efficiency. During severe drought, both species showed reductions in Pn and gs when growing near the cliff edge. In the deciduous forest, in contrast, Pn of T. occidentalis, but not A. saccharum, was significantly reduced, suggesting that A. saccharum may outcompete T. occidentalis for water. In the spring and fall, T. occidentalis had higher Pn and gs in the deciduous forest than at the cliff edge. However, all differences in gas exchange rates between trees in the deciduous forest and at the cliff edge were small and relatively rare. During most of the growing season, Pn and gs differed little between saplings in the two zones. This suggests that the pattern of abundance is not controlled to a substantial degree by carbon gain at the sapling stage. Key words: photosynthesis, water potential, Acer saccharum, Thuja occidentalis, plant zonation, cliff–forest ecotone.

Organization of the Niagara Escarpment cliff community. II. Characterization of the physical environment

1990 ◽  
Vol 68 (9) ◽  
pp. 1931-1941 ◽  
Author(s):  
R. M. Bartlett ◽  
U. Matthes-Sears ◽  
D. W. Larson
Keyword(s):  
Soil Moisture ◽  
Physical Environment ◽  
Acer Saccharum ◽  
Environmental Gradient ◽  
Deciduous Forest ◽  
Thuja Occidentalis ◽  
Active Radiation ◽  
Niagara Escarpment ◽  
Forest Habitats

In cliff-edge forests along the Niagara Escarpment, an array of species, including Thuja occidentals, is restricted to the cliff edge while different species, including Acer saccharum, are increasingly dominant away from the cliff on the plateau. This paper presents detailed analyses of 13 components of the physical environment, measured over an 18-month period, as they change across the plateau and towards the cliff edge. Statistically significant differences between the cliff-edge habitat and the adjacent deciduous forest were found in most of the 13 variables, and the results indicate a strong environmental gradient between the cliff edge and deciduous forest habitats. Lower and more rapidly fluctuating soil moisture levels combined with low photosynthetically active radiation at the cliff edge suggest that conditions there are frequently more severe for plants than in the deciduous forest in summer. Additionally, the cliff edge was snow free during the winter and the soils were frozen for a more protracted period than the deciduous forest soils. Soil and litter depths decreased significantly from the deciduous forest toward the cliff edge. The effects of these differences are discussed with reference to the characteristics of species that dominate the deciduous and coniferous cliff-edge zones. Key words: cliff, gradient, Thuja occidentalis, Acer saccharum, microclimate, Niagara Escarpment.

Comparative responses of Lolium perenne and Phalaris aquatica to multiple growth stresses

2006 ◽  
Vol 46 (9) ◽  
pp. 1131 ◽  
Author(s):  
B. R. Cullen ◽  
D. F. Chapman ◽  
P. E. Quigley
Keyword(s):  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Nitrogen Limitation ◽  
Nitrogen Availability ◽  
Nitrogen Deficiency ◽  
Distribution Patterns ◽  
Carbon Distribution ◽  
Physiological Basis ◽  
Growth Stresses ◽  
Phalaris Aquatica

The growth and carbon distribution patterns of perennial ryegrass (Lolium perenne L. cv. Yatsyn1) and phalaris (Phalaris aquatica L. cv. Holdfast) were analysed in response to defoliation and limited nitrogen availability stresses, imposed both individually and in combination. Both species showed similar responses to defoliation and nitrogen limitation when applied individually. Defoliation increased proportional export of carbon from residual leaves and carbon distribution to tillers was increased at the expense of roots. Nitrogen deficiency resulted in increased export of carbon to the root system. These results are consistent with source–sink theory. A key finding from this study was that the species responded differently when defoliation and nitrogen limitation were imposed simultaneously. Under these conditions, carbon distribution patterns in phalaris resembled those seen in plants subjected to nitrogen stress, that is, favouring root growth. The response of perennial ryegrass was to continue to support shoot growth at the expense of roots. These results suggest a physiological basis for the poor survival of perennial ryegrass often observed under continuous grazing in dry regions of southern Australia. Results are discussed in relation to the environments to which each species is adapted, and the management requirements for species persistence in marginal environments.

How to Psychologically Minimize Scratching Impulses

2014 ◽  
Vol 222 (3) ◽  
pp. 140-147 ◽  
Author(s):  
Ariane Sölle ◽  
Theresa Bartholomäus ◽  
Margitta Worm ◽  
Regine Klinger
Keyword(s):  
Cognitive Processes ◽  
Placebo Effect ◽  
Psychological Factors ◽  
Pharmacological Treatments ◽  
Physiological Basis ◽  
Psychological Mechanisms ◽  
Physical Complaints ◽  
Factors Influencing ◽  
The Impact ◽  
Placebo Model

Research in recent years, especially in the analgesic field, has intensively studied the placebo effect and its mechanisms. It has been shown that physical complaints can be efficiently reduced via learning and cognitive processes (conditioning and expectancies). However, despite evidence demonstrating a large variety of physiological similarities between pain and itch, the possible transfer of the analgesic placebo model to itch has not yet been widely discussed in research. This review therefore aims at highlighting potential transfers of placebo mechanisms to itch processes by demonstrating the therapeutic issues in pharmacological treatments for pruritus on a physiological basis and by discussing the impact of psychological mechanisms and psychological factors influencing itch sensations.

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